Wilfried Karmaus

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EPI 824 Reproductive outcomes

• Wilfried Karmaus
• Department of Epidemiology, MSU
• karmaus_at_msu.edu
• You find class material in
• http//www.msu.edu/course/epi/824/

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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

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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
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Scales

• Nominal scale (no inherent order)
• Ordinal scale
• Continuous scale (interval scale, ratio scale,
  discrete data counts
  )

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

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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/inde
  x.asp for Jacobs Institute of Womens Health
  http//www.jiwh.org)

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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.

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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

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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)
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Reproductive outcomes (markers)

• Behavioral markers
• Contraceptive use
• Planning a baby
• Frequency of sexual intercourse
• Number and gender of partners
• Use of fertility services

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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

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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.

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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.

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Validity and Reliability

• Validity of a measurement We have a gold
  standard.
• Pap smear and biopsy
• Circumcision status and physicians
  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.

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Assessment of validity of a measurement
Truth
positive predictive valuea/(ab)
negative predictive value d/(cd)
Sensitivity Pr(classified diseased?truly
diseased) a/(a c)
Specificity Pr(classified non-diseased? truly
non diseased) d/(b d)
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Validity of a measurement criteria -
specificity and - sensitivity
Sensitive tests high detection rate of persons
truly diseased (or truly exposed) Specif
ic tests high detection rate of persons
free of disease (or free of exposure) S
ensitivity and specificity of a test are
independent of the prevalence of the disease
(exposure).
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Reproducibility of a measurement Reliability
Comparing measurements, not with a gold
standard.

• Inter-rater (between observer)
• Intra-rater (test retest, within observer)

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