EPI 824 Reproductive outcomes

1. EPI 824 Reproductive outcomes Wilfried Karmaus Department of Epidemiology, MSU karmaus@msu.edu You find class material in: http://www.msu.edu/course/epi/824/

2. Content • Scales • Incidence, point / period / lifetime prevalence • Sources of information • Methods of determination • Reproductive markers (outcomes) • Time-related • Variable or stable characteristic • Validity and reproducibility

3. Epidemiology = Bridge between natural an social science and statistical models Science to describe distribution of health and its risk factors in a population Natural and social science Statistical models that describe different distribution

4. Scales Epidemiologic measures • Incidence = change of status over time = rate (time is in the denominator) • Prevalence = proportion = risk • Point prevalence (on this day etc., in this exam) • Period prevalence (in the last 3 months, 12 months, etc. • Life time prevalence: “ever experienced” • Nominal scale (no inherent order) • Ordinal scale • Continuous scale (interval scale, ratio scale, discrete data [counts] )

5. Sources of information • Collection of new data (interviews, clinical, blood, human milk, placenta, amniotic fluid, etc.) • Files (medical files, company files, etc.) • Public records (birth registry, natality statistics, grave yards, birth defects, for Michigan: http://www.mdch.state.mi.us/pha/osr/index.asp for: Jacobs Institute of Womens Health: http://www.jiwh.org)

6. Methods of determination • Interviews, questionnaires • Abstract existing files • Clinical investigations: breech or cephalic presentation, malformations, birth weight, head circumference, ultrasound examinations, etc. • Biochemical measurements: hormones, AFP, pregnancy tests, etc.

7. Reproductive outcomes (markers) • Time-related markers • age at menarche • age at menopause • age at first intercourse • interval between menarche and first intercourse • age at first marriage • cycle length, duration of menstruation

8. Reproductive outcomes (markers) • Time-related markers • gestational age • LMP (date of last menstrual period before conception) • Time to pregnancy (TTP) • Periods of unprotected TUI intercourse not leading to (time of pregnancy (PUNP) unprotected intercourse) (time of unprotected intercourse)

9. Reproductive outcomes (markers) • Behavioral markers • Contraceptive use • Planning a baby • Frequency of sexual intercourse • Number and gender of partners • Use of fertility services

10. Reproductive outcomes (markers) • Pregnancy characteristics / reproductive history • Gravidity • Parity • Plurality • Pregnancy outcome (stillbirth, live birth, induced abortion, miscarriage, ectopic pregnancy, etc.) • Gender of the offspring • Number of children

11. Reproductive outcomes (markers) • Clinical characteristics • Fetal growth (ultrasound) • breech / cephalic delivery • birthweight, size, head circumference • placental markers • malformations • retinopathy of prematurity • fibroids, neoplasm • genital and breast development (Tanner stages) • variocele, PID, etc.

12. Reproductive outcomes (markers) • Biochemical characteristics Male: • hormones • sperm count / motility Female: • hormones • AFP, etc. Pregnancy: • pregnancy test, hormone profiles • immunological markers, RH-, ABO-system • bilirubin, etc.

13. Validity and Reliability • Validity of a measurement: We have a gold standard. • Pap smear and biopsy • Circumcision status and physician’s examination by questionnaire • Reliability or reproducibility of a measurement: We compare two or more proxy-measurements or two or more determination of the gold standard.

14. result of the test disease no disease disease a=true positive b=false positive no disease c=false negative d=true negative Assessment of validity of a measurement Truth positive predictive value=a/(a+b) negative predictive value = d/(c+d) Sensitivity = Pr(classified diseasedtruly diseased) = a/(a + c) Specificity = Pr(classified non-diseased truly non diseased) = d/(b + d)

15. Validity of a measurement criteria: - specificity and - sensitivity Sensitive tests: high detection rate of persons truly diseased (or truly exposed) Specific tests: high detection rate of persons free of disease (or free of exposure) Sensitivity and specificity of a test are independent of the prevalence of the disease (exposure).

16. OBSERVATION A abnormal normal OBSERVATIONB abnormal a b row1 normal c d row2 col1 col2 total Reproducibility of a measurement = Reliability Comparing measurements, not with a gold standard. • Inter-rater (between observer) • Intra-rater (test – retest, within observer)

17. Reproducibility of a measurement ·Discrete variables: kappa coefficient ·Continuous variables: intra-class correlation coefficient (ICC) perfect agreement: kappa = 1 chance agreement: kappa = 0

18. Take home points • Reproductive epidemiology uses a wide range of measurement methods. • Time-related measurements are common variables in reproductive epidemiology. • We cannot not easily express all variables as incidence or prevalence. • Questionnaires and registry data are frequently applied to determine the burden of health problems. • Specific and more costly procedures are used to determine the etiology of adverse outcomes in smaller samples.