a List significant risk factors and their adjusted OR of BV which were found in this a Why the researcher calculate that adjusted OR? NOTE: Below are the advantageous and weakness of epidemiological study design

Jadi untuk 95 CI, alpha nya berarti 5  di “Table Z” dicari nilai Z dari 1-α2 yaitu 1-0.025 atau nilai Z 0.975  yaitu 1.96 Kalau yang dicari adalah 99 CI  dilihat di “Tabel Z” adalah nilai Z 0.995 yaitu 2.57

5. a List significant risk factors and their adjusted OR of BV which were found in this

study b List not significant risk factors of BV which were found in this study. 6. a Why the researcher calculate that adjusted OR? b Which one is correct term, OR odds ratio or prevalence ratio? Note: See Widagdo page 102. 7. a What is the main weakness of this study? b List other weakness of this design. c List advantageous of this design. Note: See Widagdo page 107.

8. NOTE: Below are the advantageous and weakness of epidemiological study design

KEUNGGULAN KELEMAHAN RANCANGANDISAIN PENELITIAN RANCANGAN KEUNGGULAN KELEMAHAN EKSPERIMENTAL MURNI 1. Merupakan rancangan yang paling kuatmeyakinkan untuk membuktikan hipotesis, karena peneliti sepenuhnya bisa memanipulasimelakukan kontrol terhadap variabel- variabel yang diteliti, baik variabel pengacauconfounding maupun terhadap variabel independent 1. Pemakaiannya terbatas hanya pada binatang dan tumbuh- tumbuhan saja EKSPERIMENTAL KUASI Clinical dan Community Trials 1. Lebih kuatmeyakinkan dibandingkan penelitian observasional. 2. Bisa dilakukan pada manusia 1. Tidak semua variabel pengacau bisa dihilangkan efeknya 2. Pemakaian pada manusia terbatas hanya untuk meneliti percobaan penyembuhan dan pencegahan penyakit saja, dan tidak bisa dipakai untuk meneliti penyebab penyakit. Udayana University Faculty of Medicine, DME 83 COHORT PROSPEKTIF 1. Angka insiden penyakit bisa diperoleh 2. Seringkali secara kebetulan dijumpai hubungan antara exposurepemaparan yang diteliti dengan penyakit yang sebelumnya tidak terpikirkan oleh peneliti 3. Karena pemaparannya terjadi pada saat sekarang maka bias dalam menetapkan exposure akan lebih kecil dibandingkan rancangan case-control 1. Pada penyakit-penyakit yang angka insidennya rendah, maka jumlah subyek penduduk sehat yang harus diamatidiperiksa secara berkala akan sangat banyak, ini memerlukan biaya, tenaga dan ketekunan yang amat tinggi. 2. Pada penyakit-penyakit yang waktu antara mulainya pemaparan dan timbulnya penyakit panjang, maka akan memerlukan waktu pengamatan yang amat lama. Akibatnya: juga memerlukan biaya, tenaga dan ketekunan yang tinggi. 3. Pada pengamatan yang lama: attritionlost to follow upakan menjadi tinggi. Ini juga amat dipengaruhi oleh tingkat mobilitas penduduk 4. Ada kemungkinan bias pada saat menentukan pembilang angka insiden, karena kemungkinan adanya kesalahan pada saat menentukan sakittidaknya subyek yang diamati. 5. Pada pengamatan yang panjang, bisa jadi KRITERIA atau CARA DIAGNOSIS penyakit telah berubah terutama pada dekade ini dimana teknologi kedokteran berkembang dengan sangat pesat. COHORT RETROSPEKTIF 1. Relatif lebih murah bila dibandingkan cohort prospektif 2. Waktu penelitian lebih pendek sehingga hasilnya cepat diperoleh 3. Sama halnya dengan cohort prospektif: angka insiden bisa dihitung sehingga RR relative risk bisa diperoleh. 1. Rancangan ini 100 tergantung dari kelengkapan pencatatan di masa lalu, baik pencatatan tentang exposure independent variable, kejadian penyakit dependent variable, dan variabel-variabel pengacau lainnya. BILA PENCATATAN TIDAK LENGKAP, MAKA BIAS NYA AKAN TINGGI. Karena rancangan ini 100 tergantung dari data sekunder, maka tidak semua variabel confounding mesti tersedia pada catatan pasien. Udayana University Faculty of Medicine, DME 84 CASE CONTROL 1. Relatif lebih rendah biayanya dibandingkan cohort prospektif. 2. Jumlah subyek yang dilibatkan dalam penelitian lebih kecil dibandingkan cohort. 3. Waktu pengamatanpenelitian lebih pendek dibandingkan cohort prospektif, sehingga hasilnya lebih cepat diperoleh. 4. Lebih tepat untuk penyakit- penyakit yang angka insidennya rendah atau yang “masa inkubasi-nya” panjang. 1. Karena menelusuri exposure di masa lalu, maka lebih besar kemungkinannya, data tentang exposure yang tersedia DARI CATATAN-CATATAN YANG ADA tidak komplit. 2. Bila exposure ditelusuri melalui wawancarainterview, karena responden harus mengingat kejadian-kejadian di masa lalu, maka lebih besar kemungkinannya mereka lupa BIAS RECALL 3. Sering kali dijumpai adanya kesulitan ketika memilih CONTROL yang betul-betul serupa dengan kelompok CASES, terutama pada rancangan mathcing. 4. Tidak bisa diperoleh RELATIVE RISK tetapi hanya estimasi perkiraan relative risk saja. Perkiraan RR ini disebut ODDS RATIO. ANALITIK CROSS- SECTIONAL 1. Karena baik faktor penyebab maupun akibat dependent dan independent variable dan demikian pula confounding variable diamati pada satu titik waktu saja, maka pelaksanaan penelitian relatif lebih cepat dibanding case-control dan cohort. 1. Rancangan ini PALING LEMAH dalam hal pembuktian HUBUNGAN KAUSAL. Kriteria hungnan temporal tidak bisa dipenuhi, karena tidak bisa diketahui, mana yang terjadi terlebih dahulu apakah independent atau independent variabelnya. Angka insiden dan RR tidak bisa diperoleh. Yang dipakai hanya OR. Self assessment 1. What are the roles of descriptive epidemiologic study designs? 2. What are the types of descriptive epidemiologic study designs? 3. Draw the figure of cross-sectional analytic study design. 4. What is the basic definition of cross-sectional and what is the procedure of the study? 5. Make one example of results analysis for analytic cross sectional design. 6. What are the advantages and disadvantages of analytic cross sectional design? 7. Can analytic cross-sectional design be applied as a basic study to find out aetiology of a disease? Udayana University Faculty of Medicine, DME 85 M O D U L E ~ 14 Greenberg, p. 113-123 Epidemiology Study Design: Cohort Study dr. I Nyoman Sutarsa, MPH dr. Putu Ariastuti, MPH AIMS: To describe cohort study design and to explain the advantages and disadvantages of cohort study to determine risk factors of diseases. LEARNING OUTCOMES: 1. To describe and to draw prospective and retrospective cohort study design 2. To explain the advantages and disadvantages of cohort study to determine risk factors of diseases 3. To explain what is relative risk and how to calculate relative risk 4. To explain the interpretation of relative risk in cohort studies CURRICULUM CONTENTS: 1. The cohort study design and its attributes 2. Timing of measurements: prospective and retrospective design 3. Subject selection in cohort studies: exposed and un-exposed groups 4. Data collection incohort studies 5. Data analysis in cohort studies: risk ratio RR and attributable risk AR ABSTRACTS A cohort study is a type of observational investigation in which subjects are classified on the basis of level of exposure to a risk factor and followed to determine subsequent disease outcome. Prospective cohort studies are conducted by making all observations on exposure and disease status after the onset of the investigation. Retrospective cohort studies involved observations on exposure and disease status prior to the onset of the study. The retrospective approach offers several pragmatic advantages, but may result in less accurate and complete information on exposure and disease status. Cohort studies are statistically efficient for the study of rare exposures because the exposed individuals can be selectively included in the study. On the other hand, cohort studies are inefficient for the investigation of slowly developing or rare diseases. The evaluation of chronic diseases through the cohort approach requires a long follow- up period and increases the chances that subjects will be lost from the study. The evaluation of rare diseases with the cohort study approach requires a large sample size and therefore is expensive and labour intensive. Udayana University Faculty of Medicine, DME 86 There are several basic strategies to analyse cohort studies. If data are collected on the risk of developing an outcome during a specified period, the summary measure of effect typically is the risk ratio. An alternative approach to contrasting risks is risk difference, which is the risk among exposed persons minus the risks among unexposed persons. If the risk difference is divided by the risk among exposed persons, a measure term the attributable risk percent is derived. The attributable risk percent is an indicator of the proportion of risk that may be attributable to the exposure. When data in a cohort study are based on the rate of disease outcome, the standard measure of effect is the rate ratio. SELF DIRECTING LEARNING: Basic knowledge and its application that students must know include: 1. Study design of cohort studies and its attributes 2. The procedures of cohort studies 3. Findings and its interpretation including crude RR, adjusted RR and attributable risk as well as confounding factors in a cohort study SCENARIO LEARNING TASKS Case 1. Please carefully study the article entitles: “Tobacco smoking as a risk factor for depression: A 26-year population-based follow up study” Learning Tasks 2: After you carefully read through the article above, please discuss the following questions: 1. Draw a figure of the study design with its attributes. 2. What are the dependent and independent variables of that study? 3. What are the confounding variables of that study? 4. Describe two major conditions of study group and control group in a cohort study 5. How did the researcher choose the control group? 6. How did the researcher control the effect of confounding variables? Is that the way by design or by analysis? 7. Explain how the researcher did that no 6 8. Why do the researchers choose this study design? Describe two reasons. 9. What is its CRUDE RR of the study? Provide the interpretation 10. What is its SPECIFIC RR after being controlled for its tobacco consumption level? Provide the interpretation Udayana University Faculty of Medicine, DME 87 Case 2. Carefully examine the following table. Socia l Class Non-Smokers Smokers All Alcohol Intake Alcohol Intake Hea vy Moder ate Light Total Heav y Moder ate Light Total I and II 118 4 579 1116 9 2733 2 628 313 126 1067 3739 9 III 422 325 1216 2 1920 9 417 27 638 1262 3127 1 IV and V 014 118 1291 1312 3 719 218 870 1710 7 3023 151 20 9122 3542 2 5966 4 176 4 738 1513 4 3923 6 9890 Learning Tasks 2: After you examined the above table, please calculate the following: 1. What is the CRUDE RR? 2. What is the SPECIFIC RR after being controlled for its social class variable? 3. What is the SPECIFIC RR after its smoking variable is controlled for? 4. What is the SPECIFIC RR after both smoking and social class variables are controlled for? 5. Provide the interpretation of thoseRR Case 3: A study at Stockholm had observed 216 children who received BCG immunization when they were aged below 6 years and 358 children who did not have BCG immunization since 1989-1992. The study was set up in 1994. In 1995-1996, all children were examined to find out atopic disease incidence atopic: a type of allergic disease. The study result shows that 36 who had BCG immunization and 41 who did not have BCG immunization are suffering from atopic disease  2 = 2.6; p 0,05. Learning Tasks 3: Based on the above case, please answer the following questions: 1. What is the study design of the case above? 2. Draw figure of the study with its attributes? 3. What is the main requirement if we want to choose that design? 4. What is the RR? 5. Does the RR in this study also occur in a population? Describe your reasons Udayana University Faculty of Medicine, DME 88 Case 4. Carefully read the article entitles: “Risk of herpes zoster among patients with chronic obstructive pulmonary disease: a population-based study” Learning Tasks 4: After you carefully read through the article above, please discuss the following questions: 1. Please draw the study profiledesign with its attributes 2. Where the exposure and the outcome data were obtained from? 3. What is the dependent and independent variables? 4. Identify the confounding variables in this study 5. What is the crude RR and what does it mean? Self Assessments: 1. What are the advantages and disadvantages of prospective and retrospective cohort studies? 2. Explain the limitation of cohort studies to determine risk factors of diseases? Udayana University Faculty of Medicine, DME 89 M O D U L E ~ 15 Greenberg, p. 127-136 Epidemiology Study Design: Case – Control Study dr. I Nyoman Sutarsa, MPH dr. Putu Ariastuti, MPH AIMS: At the end of this module, students are expected to be able to describe case-control study and to explain the advantages and disadvantages of case-control study to determine risk factors of diseases. LEARNING OUTCOMES: 1. To describe and to draw case-control study design 2. To explain the advantages and disadvantages of case-control study to determine risk factors of diseases 3. To explain what is odd ratio OR and how to calculate OR 4. To explain the interpretation of OR in a case control study CURRICULUM CONTENTS: 1. The case-control study design and its attributes 2. Case and control definition 3. Determination of exposure 4. Selection bias in case-control study 5. Matching strategy in case-control study 6. Data analysis in case control: OR and its interpretation ABSTRACTS A case-control study is a type of observational investigation in which subjects are enrolled on the basis of the presence or absence of a particular disease and are then evaluated to determine their history of prior exposure to risk factors of interest. The advantages of this design are primarily logistical. In particular, rare disease and those with long latency periods can be studied efficiently. The sample size required for a case control study tends to be smaller than would be needed for an alternative Udayana University Faculty of Medicine, DME 90 design, such as a cohort study. As a result, the expense of conducting a case-control study may be substantially less than the cost of conducting a cohort study. Furthermore, reliance on historical information allows rapid completion of case-control study. The ability to reach a prompt conclusion is particularly important if the disease of interest is potentially life-threatening. The disadvantages of case-control studies relate primarily to their susceptibility to systematic errors. Because cases and controls are sampled separately, it is possible that these groups may not arise from the same source population. Bias can be introduced into the study results if exposure status is associated with the likelihood of including cases or controls into the study. Reliance on subject recall of earlier exposures or the use of historical records can lead to imprecise or inaccurate classification of exposure. The decision to conduct a case control study typically is motivated by a desire to exposure the relationship between prior exposure to a specific risk factor and the likelihood of developing a particular disease. Ideally, the cases and the controls should derive from a single well-defined source population, such as a state or metropolitan area population-based sampling scheme. An attempt may be made to identify all newly diagnosed cases incident cases within the source population, particularly when the disease is rare or the source population is modest in size. Cases may be identified from hospital record, surveillance system, death certificates, or other sources. Careful criteria for the presence of disease must be established to minimize false inclusions or exclusions. Controls typically are sampled from the population that gave rise to the cases. Occasionally, for purposes of convenience, hospital based samples of cases and control are selected. The hospital based approach tends to have the advantages of accessibility to the subjects and cooperative study participants. On the other hand, cases and controls may derive from dissimilar source populations in a hospital-based study and prior exposure status might influence the likelihood of inclusion in this type of investigation. Matching of controls of cases on the basis of known risk factors for the disease of interest is a common practice in case-control studies. The intent of matching is usually to decrease the possibility of confounding, or mixing of the effectof exposure to the risk factors. Matching can increase the statistical precision of estimates and thereby allow a smaller sample size. On the other hand, matching can be time consuming, and subjects who are not successfully matched must be discarded from the analysis. The process of selection of subjects in a case-control study precludes the estimation of risk or rates, and the risk ratio therefore cannot be calculated directly from case-control data. An indirect estimate of the risk ratio, however, can be calculated in a case-control study. This measure is referred to as the odds ratio and is defined as the odds of exposure among cases divided by the odds of exposure among cases divided the odds of exposure among controls. The approach to calculating the odds ratio depends on whether cases and controls were sampled in an unmatched or matched fashion. In instance, a point estimate and 95 confidence interval for the odds ratio can be calculated as a measure of association between prior exposure to the risk factor and occurrence of disease. SELF DIRECTING LEARNING: Basic knowledge and its application that students must know include: 1. Case-control study design and its attributes 2. The procedures of a case control study Udayana University Faculty of Medicine, DME 91 3. Findings and its interpretation including crude OR, adjusted OR as well as confounding factors in case-control study SCENARIO LEARNING TASKS Case 1. Please carefully study the article entitles“Prolonged breastfeeding reduces risk of breast cancer in Sri Lankan women: a case-control study” Learning Tasks 1: After you carefully read through the article above, please discuss the following questions: 1. Draw a figure of the study with its attributes. 2. Was this study hospital based or population based or combination? 3. Explain its dependent and independent variables 4. Explain its case definition 5. Explain the source and methods of selecting control from the study 6. Is the above study part of a match-paired design? Why or why not? Describe three reasons. 7. Do the cases represent their population? Do the controls represent their population? 8. Are cases and controls comparable? If not, which part is not comparable? 9. How does the researcher control the effect of confounding variables? 10. What is its CRUDE OR? Provide an interpretation Case 2. Carefully examine the following table. Table 2.1 Use of IUD in sometime pregnant and never pregnant patients and controls in different age groups Age grou p yea r Patients Control Sometime Pregnant Never Pregnant Total Sometime Pregnant Never Pregnant Total IUD No IUD IUD No IUD IUD No IUD IUD No IUD ≤ 15 1 7 8 3 3 16- 20 13 44 27 93 177 5 19 7 196 227 21- 25 26 74 28 87 215 25 131 7 163 326 Udayana University Faculty of Medicine, DME 92 26- 30 20 50 3 19 92 21 86 3 49 159 31- 35 7 12 1 3 23 4 21 1 26 Tota l 66 181 59 209 515 55 257 17 412 741 Learning Tasks 2: After you examined the above table, please calculate the following: 1. What is the CRUDE OR? Please provide an interpretation 2. Calculate 95 CI confidence interval of the CRUDE OR using below formula: 3. After it is controlled for age variable, what is its SPECIFIC OR? What is the interpretation? 4. What is the SPECIFIC OR after being controlled for obstetric history variable? What is the interpretation? Case 3: Carefully read the article entitles: “Risk factors for psoriasis: a case control study” Learning Tasks 3: Based on the above case, please answer the following questions: 1. What is the dependent or response variable of this study? 2. What are the objectives of this study? 3. What are risk factors investigated or what are independent variables of this study? 4. Was this study hospital based or population based? 5. How long the cases were collected? 6. Who was the control group? 7. Regarding which variables cases and control was comparable? a Regarding which variables cases and control was not comparable? bWhat must be done to control these confounding variables? 8. See Table-3. How do you determine the most dominant risk factors? 9. See Table-3. Which risk factor had the highest OR? What was the 95 CI for this risk factor? 10. What were the OR and 95 CI of variable place of recidence? Explain, what does