Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

Bogdan Ž. Stefanovi ć Department of Forestry, Faculty of Forestry, University of Belgrade, 1 Kneza Viseslava St., Belgrade 11030, Serbia Department of Forest Roads, SE “Serbia forests”, 113 Mihajla Pupina Bvd., New Belgrade 11070, Serbia

Abstract: The paper provides an overview of geometric solutions of marking all types of serpentine by the method of internal circular curve in designing forest roads directly in the field. The main objective of presenting this original method for marking all serpentine types in one place is to show similarities and differences in marking different types of serpentine, and identify opportunities for further research of this type. The method is based on the establishment of the minimum number of elements necessary to mark the serpentine on the forest roads and other budget elements and their design in the field. By using this method, construction errors or the number of attempts of serpentine marking are reduced, which increases the effects of design compared to the ones reached by the previous method of marking the serpentine on forest roads.

Key words: Forest roads, symmetric serpentine, asymmetric serpentine, full serpentine, half serpentine, internal circular curve method, Serbia.

1. Introduction and input and output curves have different directions

(left and right) and different radii R u ≠R i . The basic geometric elements of serpentines (complex In half serpentines (Fig. 4), the center of the base or combined curves) on forest roads are: base curve, curve ( О) is not on the centerline of refraction angle β n , input and/or output curves and directions. Directions but on the line perpendicular to one of the tangents, so connect input and output curves with the base curve. there are no input or output curves. The half According to the relative disposition of the geometric serpentine on forest roads is the most common mark elements, serpentines can be divided into 1st order

on the field [2].

serpentines—symmetric and asymmetric, and 2nd The selection of the serpentine type in forest road order serpentines—full and half serpentines [1]. construction depends on the characteristics of the In symmetric serpentines (Fig. 1), the center of the route section suitable for its location, i.e. on its base curve (O) is located on the centerline of position relative to the vertex and the center of the refraction angle β n , while input and output curves have serpentine base curve. The criteria for the selection of the same direction (left or right) and equal radii R u =R i . sites suitable for the location of a serpentine and In asymmetric serpentines (Fig. 2), the center of the determining the position of its center depend on local base curve (O) is not on the centerline of refraction terrain conditions. The construction design of the angle β n , but input and output curves have the same serpentine should enable the use of the largest direction (left or right) and equal R u =R i or different possible radius of the base curve with as little radii R u ≠R i . earthworks and artificial terrain protection as possible. In full serpentines (Fig. 3), the center of the base These road sites include terrains with a moderate slope, curve ( О) is not on the centerline of refraction angle β n , natural plateaus, terrains that require smaller volume

of rock works, sites with better drainage, stable Corresponding author: Bogdan Ž. Stefanovi ć, M.Sc., research field: forest road engineering.

terrains, etc [3].

40 Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

the so-called simplified method of forest road design [4]. The theory and practice of forest road engineering in Serbia have given a positive opinion on this method of forest road design [5], because it is simpler in comparison to the public transport road design, and its

use ensures sufficient accuracy needed for the construction of forest roads [6]. The current method of forest road design should be improved [7] by simplifying certain operations of data surveying in the field. It would further facilitate the designing process and increase its efficiency.

Fig. 1 Symmetric serpentine.

The principles and the geometry of the existing method are thoroughly explained and presented in

Fig. 2 Asymmetric serpentine.

figures for symmetric [8], asymmetric [9], half serpentine [10] and full serpentine [11] in order to

analyze them and identify their methodological shortcomings with an aim to investigate, find and offer a new method of marking forest road serpentines. Namely, the author’s experience in the design of serpentine [12-14] shows that they are, in terms of design, very complicated elements of road routes, which require not only solid technical knowledge but extensive experience in route marking and selecting the geometry of serpentine, as well as good spatial orientation in the forest [15]. In addition, it has been

Fig. 3 Full serpentine.

observed that the serpentine marking directly in the field by the so-called simplified method of forest road

design has organizational shortcomings which often result in the failure to mark the serpentine at the first attempt so that the entire process has to be repeated several times [16]. This is especially true with inexperienced designers because the design of forest roads is a highly subjective and intuitive job.

In the design of serpentines directly in the field by the simplified method, we first select the center of the base curve, then mark the entire circle of the base

Fig. 4 Half serpentine.

curve and finally position the beginning point ( РК о ) and the end point ( КК о ) of the base curve on the circle.

1.1 The Problem of Serpentine Design These points are then used to design the direction of

The design of forest road serpentines in Serbia is auxiliary curves and determine the position of their done while marking the route, directly in the field by

vertices. It is only then that we can calculate the

Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

values of the geometric elements necessary for the serpentine. In addition, previous studies related to this marking of serpentines. The biggest problem in the

issue have been thus systematized and presented to the process of serpentine design is to meet the relevant scientific and professional community [17]. requirement of the minimum radius of the auxiliary

2. Material and Method

curves that has been set in advance as part of the project task. If the designed serpentine elements do

The design and marking of all types of serpentine not meet the requirement of the minimum radius,

by the method of internal circular curve was primarily another beginning point ( РК о ) and end point ( КК о ) of

performed by using the method of comparative the base curve have to be selected. If several attempts

analysis. Apart from it, we used the modeling method, of marking fail, the whole procedure must be repeated

by applying mathematical, geometric and from the point of selecting the position of the center or

trigonometric relations and visualization. the radius of the base curve, or even the whole

The marking out of the serpentines by the internal serpentine has to be repositioned.

circular curve method is based on the necessary amount of measured data and the calculation of the

1.2 The Idea of New Serpentine Design necessary elements for the serpentine marking. The

This old method of serpentine marking is complex data for serpentine marking by this method are and it is not effective. Therefore, we have come to an

obtained on the basis of the calculations related to the idea to explore a new method of serpentine design

“interior part of the serpentine base curve”. Namely, which would overcome the observed problems. The

beginning point ( РК о ) and end point ( КК о ) of the resulting methodology solution is presented as a new

serpentine base curve divide the base circle into two method of marking symmetric [8], asymmetric [9],

circular arcs. One of them is an integrate part of the full [11] and half serpentines [10] on forest roads,

serpentine, being the circumference of the base curve. called the internal circular curve method.

The other curve is on the interior side of the circle in The main idea of the proposed method is to make

relation to the whole serpentine (this part of the circle the field work more effective and to optimize the

is in all figures given in this paper marked with a design of serpentine. The effectiveness is achieved by

dotted line). If we set the tangents to the circular curve changing the sequence of the marking operations and

that is on the interior side of the circle at beginning by surveying the minimum amount of data necessary

( РК о ) and end ( КК о ) points of the base curve and to calculate the serpentine elements. The possibility of

intersect them we obtain vertex ( Т o ) of the interior errors and the time needed for the design are thus

curve with refraction angle β о .

reduced. As its effectiveness increases, the serpentine

3. Results and Discussion

design becomes more optimized. The paper provides an overview of the

For the successful application of the internal methodology of marking all types of serpentine on

circular curve method, there is one basic condition forest roads by the method of internal circular curve.

that has to be satisfied in the field: refraction angle β n The main goal is to make a comparative analysis of

of the route directions should be measurable, i.e. the the required length and angle measurements as well as

position of vertex ( Т n ) must be determined in the field. the calculations of the elements necessary for the

3.1 Results

marking and to present the process of marking all types of serpentine in the field by showing the

As with the simplified method of laying out forest similarities and differences in marking certain types of

roads, the first step is to determine the directions of

42 Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

the route intersecting in vertex ( Т n ) using at least three poles. Pole  is set on the serpentine vertex ( Т n ), and in the direction of the previous (T n-1 ) and the subsequent vertex (T n+1 ) poles  and  are aligned.

Marking all types of serpentine in the field by the method of internal circular curve includes the following stages:

1. From the serpentine vertex ( Т n ) in the direction of the previous (T n-1 ) and the following vertex (T n+1 ) measure pre-selected lengths b p , b u and b i and with poles  and  mark the vertices of auxiliary curves ( Т р ). In symmetric serpentine (Fig. 5) lengths b p are equal, while asymmetric (Fig. 6) and full (Fig. 7)

serpentine have different lengths b u and b i . In half

Fig. 7 Marking of the full serpentine by internal circular

serpentine (Fig. 8), one vertex of auxiliary curve ( Т р )

curve method.

is marked with pole  and length b p is measured.

2. From the vertex of auxiliary ( Т р ), input ( Т u ) and output (T i ) curves, directions of the tangents to the future base circle are marked and the turning angles of

Fig. 8 Marking of half serpentine by internal circular curve method.

Fig. 5 Marking of symmetric serpentine by internal circular curve method.

input α u and output α i curves are measured for asymmetric (Fig. 6) and full (Fig. 7) serpentine. In

symmetric serpentine (Fig. 5), turning angles α р of auxiliary curves are equal, so only one of them is measured. The same applies to half serpentine which has only one turning angle α р of the auxiliary curve (Fig. 8).

3. Calculation of geometric elements for serpentine marking

The measured lengths b p , b u , and b i and angles β n , α р , α u and α i are used to calculate the elements of serpentine marking:

 Calculating the length of inner curve tangent

Fig. 6 Marking of asymmetric serpentine by internal circular curve method.

t о (m)

Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

where d p is the length between the vertices of t o  R o  ctg

2 auxiliary curves and vertex Т о , d u is the length The length of radius R о of the base curve is

between the vertex of input curve and vertex Т о and d i determined by the designer based on the is the length between the vertex of output curve and characteristics of the serpentine site. The minimum

vertex Т о .

length of radius R о of the serpentine base curve is 12 Lengths d p (m), d u (m) and d i (m) are calculated m [18].

based on the law of sines in Т u Т о Т i by the following Calculating refraction angle β о (˚)

formulas:

symmetric serpentine

sin 

(12) sin  o asymmetric serpentine

half serpentine

sin  n

(13) sin  o full serpentine

i     u     180

asymmetric and full serpentine

sin 

(14) sin  o half serpentine

 o        i   u   180 

sin 

(15) sin  o  o   p   n

Angle γ (˚), depending on the type of serpentine, is Angles  ˚) and (  ˚) are calculated based on the (

calculated by the following formulas: law of sines in  Т u Т n Т i by the following formulas:

symmetric serpentine

  180  n      p 

b sin   u sin     arcsin 

(16) L

b asymmetric and full serpentine

sin   i sin  n    arcsin 

 180        i 

(17) and the length L (m) between the vertices of the input

and output curves is calculated based on the law of While angle δ (˚), in the asymmetric and full

cosines in  Т u Т n Т i by the following formula: serpentine is calculated by the formulas: asymmetric serpentine

u  b i  2  b u  b i  cos  n

  180       u 

(18) Calculating lengths l p (m), l u (m) and l i (m) needed

full serpentine

to mark points РК о and КК о

  180      u 

symmetric and half serpentine

Calculating the length of tangent of auxiliary t (9) р (m) input t u (m) and output t i (m) curves

asymmetric and full serpentine

symmetric and half serpentine

t p  l p  a p (20)

asymmetric and full serpentine (11)

44 Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

- calculating angles  and  by formulas 6 and 7,

(21) - calculating refraction angle β о by formulas 2, 3, 4

and 5,

(22) - calculating the length of tangent t о by formula 1,

where a р is the length between the base and auxiliary - calculating angles  and  by formulas 16, 17, 18 curves, a u is the length between the base and the input

and 19,

curve and a i is the length between the base and output - calculating lengths d р , d u and d i by formulas 12, curve.

13, 14 and 15,

The minimum length of the straight section a min (m) - calculating length l р , l u and l i by formulas 9, 10 of forest roads is equal to the double length of the

and 11,

transition ramps l r (m). The length of the transition - calculating the length of tangents t р , t u and t i by ramps on the forest roads is l r = 10 m [4], so that the

formulas 20, 21 and 22,

min length of the straight sections between the base - calculating the length of radii R р , R u and R i by and the auxiliary curve is a min = 20 m.

formulas 23, 24 and 25.

4. Beginning point ( РК о ) and end point ( КК о ) of the auxiliary R р , input R u and output R i curves

Calculating the required length of the radius for

base curve are marked based on the calculated lengths The accuracy of the design of all types of serpentine

l р , l u and l i . We measure the lengths l р , l u and l i from by the method of internal circular curve is checked by

the vertex of auxiliary ( Т р ), input ( Т u ) or output (T i ) calculating the length of auxiliary R р (m), input R u (m)

curves in the direction of turning angles α p of auxiliary and output R i (m) curve radii, by the following

input α u and output α i curves, and mark beginning formulas:

( РК о ) and/or end points ( КК о ) of the base curve. In the symmetric and half serpentine

field, these points are on the symmetric (Fig. 5),

asymmetric (Fig. 6) and full (Fig. 7) serpentines R p 

marked with poles  and , and on the half

2 serpentine with pole  (Fig. 8).

asymmetric and full serpentine

5. Perpendicular lines are constructed at beginning

point ( РК о ) and end point ( КК о ) of the base curve to R u  u

tangent РК о - Т u and КК о -T i . The intersection of

2 perpendicular lines in symmetric (Fig. 5), asymmetric

(Fig. 6) and full (Fig. 7) serpentine produces central R i  i

point (O) of the base curve, which is in the field

2 marked with a peg and pole . The distance between If the calculated radii of auxiliary curves are at

РК о or КК о and center (O) of the base curve is R o , least two or three times greater than the radii of the

which should equal the selected value of the radius base curve [4] the serpentine can be marked.

used in formula 1 calculation.

Otherwise, survey of the data necessary for a repeated In half serpentine the length of radius R o of the base calculation of geometric elements should be curve is added to the normal line in the direction of performed.

tangent line РК о - Т р or КК о -T р and center (O) of the The elements necessary for serpentine marking are

base curve is determined. The center of the base curve calculated in the following order:

is marked with a peg and pole  (Fig. 8). From the - calculating length L by formula 8,

center point (O) of the base curve a normal line is

Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

constructed in the opposite direction of the route work, because we do not mark the entire base curve, (whose length b p has not been measured) and

but only its main points which are then used to beginning point ( РК о ) or end point ( КК о ) of the base

perceive the whole serpentine.

curve are marked. This point is in the field marked The internal circular curve method is an innovation with pole . The accuracy of the calculation and

based on an original idea that originated from the marking can be tested by checking whether the

attempts to overcome the perceived problems with length of the normal from center point (O) to start

serpentine marking on forest roads. The method is point ( РК о ) or end point ( КК о ) of the base curve

named internal circular curve because it is used for the equals the pre-selected length of radius R o of the base

calculation of the basic elements of the inner circle of curve.

the serpentine curve and it is similar for all types of

6. Directions of radius R o of base curve О-РК о and

serpentine.

О-КК о make central angle  о . When the centerline of The proposed method of serpentine marking, this angle is marked in the field and the length of

presented in this paper, needs to pass various tests and radius R o of the base curve added along it from center

checks before it is applied and verified in practice. Its (O) of the base curve, we obtain mid-point (S К о ) of

application and improvement open a range of issues the base curve. This point is on the symmetric (Fig. 5),

related to technical constraints and organizational asymmetric (Fig. 6) and full (Fig. 7) serpentine

solutions such as: research into the relations between marked with pole , and this point is on the half

individual elements of the serpentine marking, testing serpentine marked with pole  (Fig. 8). By observing

the limit values of serpentine geometric elements, its position in the field and the position of other points

comparing the time needed for serpentine marking by marked on the serpentine: center (O), beginning point

the old and the new method and assessing the ( РК о ) and end point ( КК о ) of the base curve, we can

performance. It is assumed that the application of this observe the position of the whole serpentine in the

method can shorten, facilitate and rationalize marking space.

forest road serpentines. However, these questions should be answered by further research.

3.2 Discussion

4. Conclusions

The internal circular curve method uses the minimum amount of necessary pre-required data to

Based on the presented method of marking all types calculate the values of other elements necessary to

of serpentine on forest roads we can draw the mark all types of serpentine. The marking out process

following conclusions:

begins by determining the position of the vertices of The previous method of marking different types of input ( Т u ) and output ( Т i ) curves, as well as input and

serpentines in the design of forest roads in the field output directions, taking into account the lengths of

had both organizational and methodological auxiliary curve tangents and straight sections. In this

shortcomings. Due to its shortcomings, it was way, it is possible to mark a curve of specific base R o ,

impossible or very difficult to achieve a satisfactory input R u and output R i radius. When we mark

solution at the first attempt. Therefore it was beginning point ( РК о ), end point ( КК о ) and mid-point

necessary to repeat the process of marking until the (S К о ) of the base curve, we can see the possibility of

best solution had been reached. It increased the time marking the entire serpentine. This practice can reduce

necessary to mark the serpentine, reduced the level of errors in determining the beginning and end points of

design performance, and consequently increased the the base curve and it can also decrease the amount of

cost of the design process in the field.

46 Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

Taking into account the perceived problems in University of Belgrade, Belgrade (in Serbian). [4] Simonovic, M., and Lalic, M. 1975. Practicum for Forest

marking all types of serpentine on forest roads, a new Road Design, Faculty of Forestry University of Belgrade,

method of serpentine marking called the internal

Belgrade (in Serbian).

circular curve method has been innovated. This [5] Stefanovic, B. Z. 1996. “Analysis of Elements of Axis method is based on the minimum amount of

Horizontal Projection of Forest Truck Road.” Forestry 6: 35-47 (in Serbian with English abstract and summary).

pre-required field data that are used to calculate the [6] Lalic, M. 1976. Feasibility Study of Application the

values of geometric elements necessary for marking Simplified Methods Making the Final Design of Forest the serpentine and then to mark them in the field. This

Roads, Ph.D. Thesis, Faculty of Forestry University of practice can reduce design errors and decrease the

Belgrade, Belgrade (in Serbian). [7] Stefanovic, B. Z. 1999. “Designing of Forest Roads:

amount of work because the serpentine geometric Basic Directions and Perspectives of Development.”

elements are calculated before they are marked in the Bulletin Faculty of Forestry 80-81: 107-17 (in Serbian field, without marking the entire base curve, but only

with English abstract and summary). its main points, based on which the entire serpentine

[8] Stefanovic, B. Z. 2005. “The Symmetric Serpentine Marking on Forest Roads by Internal Circular Curve

can be marked. Method.” Bulleting Faculty of Forestry 91: 219-29 (in

The internal circular curve method of serpentine Serbian with English abstract and summary). marking uses the elements of the inner circle of the

[9] Stefanovic, B. Z. 2005. “The Asymmetric Serpentine serpentine base curve which makes it similar for all Marking on Forest Roads by Internal Circular Curve Method.” Forestry 3: 107-16 (in Serbian with English

types of serpentine. However, the geometric

abstract and summary).

construction of each type of serpentine is different, so [10] Stefanovic, B. Z. 2009. “The Half Serpentine Marking on the amount of data to be surveyed is different, as well

Forest Roads by Internal Circular Curve Method.” as the method of calculation. However, the procedure

Bulleting Faculty of Forestry 99: 155-64 (in Serbian with English abstract and summary).

and the sequence of marking do not differ [11] Stefanovic, B. Z. 2009. “The Full Serpentine Marking on significantly. When surveying data for symmetric

Forest Roads by Internal Circular Curve Method.” serpentine, 3 data items are recorded, and 5 elements

Bulleting Faculty of Forestry 11, University of Banja are calculated to obtain the marking elements. In Luka, Srpska, Bosnia and Herzegovina: 123-35 (in Serbian with English abstract and summary).

asymmetric and full serpentine 5 data items are [12] Stefanovic, B. Z. 2002. Final Design of Forest Track

recorded and 13 elements calculated, while half Road “Golaca-Jovanov Laz-Bodevik” length 3.22 km, serpentine requires 3 data items and 4 elements.

investor: FE “Toplica” Kursumlija, project owner:

4. The use of the internal circular curve method for Institute of Forestry, PE “Serbia forests” (in Serbian). [13] Stefanovic, B. Z. 2002. Final Design of Forest Track

marking all types of serpentine on forest roads Road “Potok Biger-Tri poljane” length 3.65 km, investor:

requires verification and application in forest FE “Severni Kucaj” Kucevo, project owner: Institute of engineering practice, but it opens a series of questions

Forestry, PE “Serbia forests” (in Serbian). related to further research and improvement of this

[14] Stefanovic, B. Z., and Mitrovic, D. 2002. Final Design of Forest Track Road “Ujevac-Severni Revir” length

method of designing forest road serpentines. 1.27 km, investor: FE “Severni Kucaj” Kucevo, project

References owner: Institute of Forestry, PE “Serbia forests” (in

Serbian).

[1] Mitin, A. N. 1972. Serpentine, Transport, Moscow (in [15] Stefanovic, B. Z. 2004. “Specificity of Planning of Road Russian).

Infrastructure in the Forest Regions of Serbia.” [2] Acimovski, R. 1953. “The Making of Serpentine on

Proceedings of BSTU 2 (12), Minsk, Belorussia: 151-6 Forest Roads.” Proceedings of Agriculture and Forestry

(in Russian with English abstract). Faculty University of Skopje, Book IV, Skopje,

[16] Stefanovic, B. Z. 2006. “Comparative Analysis of Two Macedonia (in Macedonian).

Methods of Making Serpentine on Forest Roads.” In: [3] Acimovski, R. 1997. Forest Engineering: Forest Road,

Proceedings of 6th International Scientific Technical

Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia

Conference “Forest Complex: State and Development Forestry Congress “Future with forests”, Faculty of Prospects”, Bryansk State Technical University, Bryansk,

Forestry, University of Belgrade, Belgrade, Serbia, pp. Russia, pp. 48-51 (in Russian with English abstract).

588-601.

[17] Stefanovic, B. Z. 2010. “Design of Serpentine on Forest [18] Butulija, S., and Radjenovic, B. 1993. Guideline for Roads by Internal Circular Curve Method.” In:

Design of Forest Truck Roads, PE “Serbia forests”, Proceedings of International Conference: 1 st Serbian

Belgrade (in Serbian).

Journal of Life Sciences 10 (2016) 48-53

doi: 10.17265/1934-7391/2016.01.007

DAVID PUBLISHING

The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing Cardiovascular Risk in Patients on Hemodialysis

Irena Ivanova Gencheva-Angelova, Adelaida Lazarova Ruseva and Pavlina Dimitrova Yordanova-Laleva UMHAT, Medical University, Pleven 5800, Bulgaria

Abstract: Cardiovascular diseases constitute approximately 50% of deaths among dialysis patients in the USA and Europe. The increase in traditional and nontraditional cardiovascular risk factors in determining the high mortality of patients with end-stage renal disease (ESRD) is complicated due to the high frequency of risk factors in these patients. Some laboratory markers like homocysteine, albumin, cholesterol, triglycerides, LDL-cholesterol, and creatinine could be efficient in marking the risk of cardiovascular disease in these patients. We use Roche assay tests, based on routinely principles to determine this laboratory parameters used in the clinical laboratory. All laboratory parameters we measured on a biochemistry auto analyser Cobas Integra 400 at the clinical laboratory of University Hospital—Pleven. Using a statistical program a research was done on the quantitative characteristics and prognostic capabilities of homocysteine and other biochemical parameters. We determined the diagnostic specificity and sensitivity of our lab performance against vascular disease (heart attack or stroke) by ROC curves. For each of the observed values of biochemical parameters we calculated the diagnostic sensitivity and specificity. The threshold values for which the parameters have the highest sensitivity and specificity have been concluded. Summary of diagnostic value of parameters to judge the coefficient AUC—area under the curve, for cholesterol, LDL, triglycerides, albumin, it was a significant (P < 0.05). Homocysteine and the rest of the studied by us laboratory parameters can be regarded as laboratory markers of choice for assessing the risk of heart attack or stroke in patients on dialysis.

Key words: Homocysteine, albumin, end-stage renal disease, cardiovascular risk factors.

1. Introduction  with the exception of research Bostom et al. [15] and Moustapha et al. [16] in a total of 240 patients there is

Cardiovascular diseases form approximately 50%

a lack of connection between hyperhomocysteinemia of deaths among dialysis patients in the USA and and cardiovascular mortality in hemodialysis patients. Europe [1]. The increase in traditional and The issue is mainly important because a recent study nontraditional cardiovascular risk factors in probed that the reduced concentration of plasma determining the high mortality of patients with homocysteine, but not hyperhomocysteinemia, end-stage renal disease (ESRD) is complicated due to predicts reducing of the risk of vascular events [17]. the high frequency of risk factors in these patients [2]. The elevated Hcy shows atherogenic and Hyperhomocysteinemia is seen as a cardiovascular prothrombotic properties and histopathologic features risk factor in patients with chronic renal damage [3] of Hcy induced vascular damage. It is included and the issue is analyzed in several studies [4-12]. In thickening of the intimal disruption elastic layer relation to this, the observation that plasma vascular smooth muscle hypertrophy, marked homocysteine level (Hcy) is independently connected accumulation of platelets and the formation of to the aortic injury [13], and left ventricular platelet-enriched blood clots. The role of hypertrophy [14] are of particular interest. However, homocysteine in coronary heart disease and stroke is

Corresponding author: Irena Ivanova Gencheva-Angelova, not yet fully understood. In some randomized studies MD, research field: clinical laboratory.

The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing

Cardiovascular Risk in Patients on Hemodialysis

is reported that reduced levels of Hcy do not reduce Patients were followed for one year within six visits the overall risk of cardiovascular disease (CVD) [18,

for development of cardiovascular event (heart attack 19].

or stroke) or death due to such. In 18 patients (10 Genest and colleagues (2000) noted the link

women and 8 men) has come vascular events—heart between high levels of Hcy and atherosclerosis. The

attack or stroke, compared with 15 of them whose reliability of information derived mainly from outcome was fatal. All samples were analyzed with case-control studies, however, the strength of this

biochemical analyzer Cobas Integra 400 in medical association is not reliable in prospective studies. Thus

diagnostic laboratory of University Hospital “Dr. the causal link between total Hcy and heart disease is

George Stransky”—Pleven.

not so reliable as to make recommendations regarding The biological material is serum, without hemolysis screening and treatment for the prevention of CVD

and lipemia.

[20]. Patients in the course of a year are monitored for American Academy of Family Physicians (AAFP

homocysteine, albumin, cholesterol, triglycerides, 2012) concluded that for coronary heart disease, the

LDL-cholesterol, and creatinine.

current evidence is insufficient to assess the balance of We use Roche assay tests, based on routinely benefits and harm of using non-traditional risk factors

principles to determine a laboratory parameters used for prevention of vascular events.

in the clinical laboratory. Determination of

Non-traditional risk factors included in this homocysteine is the principle of testing the enzymatic recommendation are highly sensitive C-reactive cycle and evaluates the product from the conversion of protein, ankle-brachial index, leukocyte count, fasting

cosubstrate instead evaluating itself cosubstrate or levels of blood sugar, gum disease, the thickness of

products from the conversion of homocysteine. The the carotid intima, coronary artery calcification, HCY

concentration of homocysteine in the sample is levels and lipoprotein (a) level and other.

proportional to the amount of NADH, NAD + in turn. In patients with end-stage renal damage that have

For the determination of serum creatinine is used an much greater degree for risk of vascular events or

enzyme method, not the widely used test based on the death from such an incident is extremely important to

principle of Jaffe. The reference values are accepted determine to what extent these factors—traditional

for the laboratory parameters of healthy individuals of and non-traditional influence.

the Bulgarian population are: albumin 35-50 g/L, Hcy

Therefore, in our research we studied 120 < 12 umol/L, Tg < 2.3 mmol/L, Chol < 5.2 mmol/L, hemodialysis patients and have them monitored for

LDL cholesterol < 3.36 mmol/L, CreaP women < 84 cardiovascular events (heart attack or stroke) for one

umol/L, male < 104 umol/L.

year. Using a statistical program is done a research on the quantitative characteristics and prognostic capabilities

2. Materials and Methods

of homocysteine and other biochemical parameters. In our study, we studied 120 hemodialysis patients,

We determined the diagnostic specificity and women and men aged from 18 to 80 years, in a V

sensitivity of our lab performance against vascular stage CKD. Except hemodialysis patients are disease (heart attack or stroke) by ROC curves. examined and healthy subjects as controls without

3. Results and Discussion

renal or cardiovascular disease. All studied patients have consented to their results to be used for scientific

The diagnostic quality of the researched by us purposes.

laboratory indicators is evaluated by ROC curves

50 The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing

Cardiovascular Risk in Patients on Hemodialysis

based on the sensitivity and specificity of the tests. (Table 3). For cholesterol, LDL, triglycerides, albumin, (Table. 1)

and it was a significant (P < 0.05) and exceeds 0.66, Under Table 1 Sensitivity is defined by the

i.e..

proportion of positive cases of the test (s) in the Each of these laboratory parameters can properly actually sick (a + b) to the group itself, i.e. attitude

diagnose sick and healthy people over 66% of patients and/(a + b), and specificity—the attitude of negative

in the sample (N = 120) compared to cardiovascular test cases according to (d) in the healthy group (c + d),

disease. For the entire population of patients with

i.e. to the relation d/(c + d). chronic kidney disease on hemodialysis (V stage) this For each of the observed values of biochemical

percentage ranged from 52.3%-80.4% (TG) to parameters we calculated the sensitivity and 62.0%-89.3% (albumin). specificity. The threshold values for which the

With diagnostic value are creatinine and parameters have the highest sensitivity and specificity

homocysteine. Their P-values (0.087 and 0.089 are shown in Table 2

respectively) are greater than the critical point of 0.05 The pairs of the corresponding numbers for their

but less than 0.10—the highest significance level, sensitivity and specificity of a given indicator are

which also applies (albeit less frequently) in reflected as points on the rectangular coordinate

biostatistical research. Under this condition, system. Once joined, the resulting polyline is precisely

homocysteine may also be used as a diagnostic test the ROC curve (Fig. 1). The area below is a measure

against cardiovascular disease. For Hcy AUC = 0.632 of to what extent the values of biochemical indicator

95% CI = 0.476 ÷ 0.788. Its threshold values are > patients in the sample can be classified into one of two

47.30 that determine sensitivity of 62.5% and groups-patients/healthy.

specificity 55.8% (Table 2).

Fig. 1 shows the ROC curves of the 6 biochemical However, the diagnostic value of homocysteine is parameters of important diagnostic role in particularly high in terms of two categories—patients cardiovascular disease, namely curves: albumin (a),

on dialysis and controls. ROC curve for this case is cholesterol (b), LDL (c), creatinine (g), homocysteine

represented in Fig. 2.

(e), TG (f). AUC ratio is equal to 0.994 (p0000) with 95% CI = Summary of diagnostic value of parameters to

0.985 ÷ 1.000. Homocysteine is practically 100 percent judge the coefficient AUC—area under the curve

of properly diagnosed group of 140 persons of two

Table 1 Evaluation of diagnostic tests.

Diagnosis Testresults All Positive Negative Sick

Table 2 The threshold values of biochemical parameters.

Parameter Thresholdvalue Sensitivity% Specificity% Albumin

LDL

Cholesterol

Triglycerides

Creatinine

Homocysteine

The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing

Cardiovascular Risk in Patients on Hemodialysis

Fig. 1 ROC curves biochemical parameters against cardiovascular disease.

52 The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing

Cardiovascular Risk in Patients on Hemodialysis

Table 3 AUC—coefficients against cardiovascular disease.

Parameter AUC

95% CI Tg

0.664 0.072 0.035 0.523 0.804 Chol 0.710 0.060 0.007 0.593 0.828 LDL 0.739 0.064 0.002 0.614 0.864 Alb 0.757 0.070 0.001 0.620 0.893 CreaP 0.633 0.067 0.087 0.501 0.766 Hcys 0.632 0.080 0.089 0.476 0.788

1992. “Report on Management of Renal Failure in Europe XXII.” 1991 Nephrol. Dial. Transplant. 7 (2): 7-35.

[2] Levey, A. S. 1998. “Controlling the Epidemic of Cardiovascular Disease in Chronic Renal Disease: Where do We Start?” Am. J. Kidney Dis. 32 (3): 5-13. Wilcken,

D. E., and Gupta, V. J. 1979. “Sulphr Containing Amino Acids in Chronic Renal Failure with Particular Reference to Homocystine and Cysteine-homocysteine Mixed Disulphide.” Eur. J. Clin. Invest 9: 301-7.

[3] Chauveau, P., Chadefaux, B., and Coude, M., et al. 1993. “Hyperhomocysteinemia, a Risk Factor for Atherosclerosis in Chronic Uremic Patients.” Kidney Int.

43 (41): 72-7.

Fig. 2 ROC curve of homocysteine in dialysis patientst

[4] Bachmann, J., Tepel, M., and Raidt, H., et al. 1995. “Hyperhomocysteinemia and the Risk for Vascular

and controls.

Disease in Hemodialysis Patients.” J. Am. Soc. Nephrol.: categories: 120—patients with chronic renal damage

121-5.

and 20—healthy controls without kidney disease. [5] Bostom, A. G., Shemin, D., and Lapane, K. L., et al. 1995. “Hyperhomocysteinemia and Traditional Cardiovascular

There is a full coverage with reality. The threshold Disease Risk Factors in End-stage Renal Disease Patients values are ≥ 15.30, which defines sensitivity of 99.2%

on Dialysis: A Case-control Study.” Atherosclerosis 114: and specificity 90.0%. These results support the thesis

93-1037. Hultberg, B., Andersson, A., and Sterner, G. of the diagnostic value of homocysteine in certain 1993. “Plasma Homocysteine in Renal Failure.” Clin.

Nephrol. 41: 230-4.

disease manifestations in patients on hemodialysis. [6] Robinson, K., Gupta, A., and Dennis, V., et al. 1996. “Hyperhomocysteinemia Confers an Independent

4. Conclusions

Increased Risk of Atherosclerosis in End-stage Renal

In conclusion we can say that there is a relation Disease and is Closely Linked to Plasma Folate and

Pyridoxine Concentrations.” Circulation 94: 2743-8. between hyperhomocysteinemia and cardiovascular

[7] Bostom, A., Brosnan, J. T., and Hall, B., et al. 1995. “Net events in patients on dialysis. Homocysteine and the

Uptake of Plasma Homocysteine by the Rat Kidney in rest of the studied by us laboratory parameters can be

vivo.” Atherosclerosis 116: 59-62.

regarded as laboratory markers of choice for assessing [8] Guttormsen, A. B., Svarstad, E., Ueland, P. M., and Refsum, H. 1995. “Elimination of Homocysteine from the risk of heart attack or stroke in patients on dialysis.

Plasma in Subjects with End Stage Renal Failure.” Ir. J. The six parameters are high diagnostic sensitivity and

Med. Sci. 164 (15): 8-9.

specificity of the risk of vascular events in patients [9] Vychytil, A., Fodinger, M., and Papagiannopoulos, M., et al. 1999. “Peritoneal Elimination of Homocysteine

with end-stage renal damage. Moieties in Continuous Ambulatory Peritoneal Dialysis

References Kidney Int. 55: 2054-61

Patients.”

http://dx.doi.org/10.1046/j.1523-1755.1999.00437. [1] Raine, A. E., Margreiter, R., and Brunner, F. P., et al.

[10] Sirrs, S., Duncan, L., and Djurdjev, O., et al. 1999.

The Role of Homocysteine and Other Clinical Laboratory Markers in Assessing

Cardiovascular Risk in Patients on Hemodialysis

“Homocysteine and Vascular Access Complications in 2000. “Hyperhomocysteinemia, Nutritional Status, and Haemodialysis Patients: Insights into a Complex

Cardiovascular Disease in Hemodialysis Patients.” Metabolic Relationship.” Nephrol. Dial. Transplant. 14:

Kidney Int. 57: 1727-35 738-43.

http://dx.doi.org/10.1046/j.1523-1755.2000.00018.x [11] Blacher, J., Demuth, K., and Guerin, A. P., et al. 1998.

[16] Foley, R. N., Parfrey, P. S., and Harnett, J. D., et al. 1996. “Influence of Biochemical Alterations on Arterial

“Hypoalbuminemia, Cardiac Morbidity and Mortality in Stiffness in Patients with End Stage Renal Disease.”

End-stage Renal Disease.” J. Am. Soc. Nephrol. 7: Arterioscler. Thromb. Vasc. Biol. 18: 534-41.

728-36.

[12] Blacher, J., Demuth, K., and Guerin, A. P., et al. 1999. [17] Zoccali, C., Mallamaci, F., and Tripepi, G., et al. 1999. “Association between Plasma Homocysteine

“Prediction of Left Ventricular Geometry by Clinic, Concentrations and Cardiac Hypertrophy in End Stage

Pre-dialysis and 24-h Ambulatory BP Monitoring in Renal Disease.” J. Nephrol. 12: 248-55.

Hemodialysis Patients.” J. Hypertens 17: 1751-8. [13] Bostom, A. G., Shemin, D., and Verhoef, P., et al. 1997.

[18] Genest, J., McPherson, R., Frohlich, J., Anderson, T., “Elevated Fasting Total Plasma Homocysteine Levels

Campbell, N., Carpentier, A., Couture, P., Dufour, R., and Cardiovascular Disease Outcomes in Maintenance

Fodor, G., Francis, G. A., Grover, S., Gupta, M., Hegele, Dialysis Patients.” Arterioscler. Thromb. Vasc. Biol. 17:

R. A., Lau, D. C., Leiter, L., Lewis, G. F., Lonn, E., 2554-8.

Mancini, G. B., Ng, D., Pearson, G. J., Sniderman, A., [14] Moustapha, A., Naso, A., and Nahlawi, M., et al. 1998.

Stone, J. A., and Ur, E. 2009. Canadian Cardiovascular “Prospective Study of Hyperhomocysteinemia as an

Society/Canadian Guidelines for the Diagnosis and Adverse Cardiovascular Risk Factor in End-stage Renal

Treatment of Dyslipidemia and Prevention of Disease.” Circulation 97: 138-41.

Cardiovascular Disease in the Adult—2009 [15] Suliman, M. E., Qureshi, A. R., and Barany, P., et al.

Recommendations.

Journal of Life Sciences 10 (2016) 54-57

doi: 10.17265/1934-7391/2016.01.008

DAVID PUBLISHING

Serpentine Design on Forest Roads by the Internal Circular Curve Method: A Case Study in Serbia