Evaluation of the Validity of the Gestational Length Assumptions Based Upon Administrative Health Plan Data Li

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Pharmacoepidemiology

Pharmacoepidemiology

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  • 1. Evaluation of the Validity of a GestationalLength Algorithm Based upon Electronic Health Plan DataQian Li, Susan. E. Andrade, William O. Cooper, Robert L.Davis, Sascha Dublin, Tarek A. Hammad, Pamala. A.Pawloski, Simone P. Pinheiro, Marsha A. Raebel, PamelaE. Scott, David. H. Smith, Inna Dashevsky, KatieHaffenreffer, Karin E. Johnson, Darren Toh 18th Annual HMO Research Network Conference, Seattle WA May 2, 2012
  • 2. Funding Source & Conflict of Interest Contracts HHSF223200510012C, HHSF223200510009C, an d HHSF223200510008C from the U.S. FDA Dr. Dublin funded by Paul Beeson Career Development Award from the National Institute on Aging, grant K23AG028954, and by Group Health Research Institute internal funds Abstract not necessarily represent official views or endorsement of the FDA or the National Institute on Aging or the NIH None of the other authors have conflict of interest
  • 3. Background Medication effects often specific to particular gestational period Electronic health plan databases are increasingly used in pregnancy research Valid prenatal exposure status  Pharmacy dispensing data  Pregnancy beginning & gestational length Computerized algorithm (delivery date + preterm birth ICD-9-CM)
  • 4. Objectives To examine the validity of a commonalgorithm by comparing  algorithm-derived gestational length & prevalence of medication exposures during pregnancy  “gold standard” measures in birth certificates
  • 5. Data Source Medication Exposure in Pregnancy Risk Evaluation Program (MEPREP) - U.S. Food and Drug Administration - HMO Research Network (8 health plans) - Kaiser Permanente California - Vanderbilt School of Medicine/Tenn Medicaid MEPREP - Enrollment - Socio-demographic (race/ethnicity) - Demographics - Medical - Outpatient pharmacy dispensing - Reproductive (parity, gestational age) - Outpatient and inpatient encounter Administrative and Birth Claims Certificate
  • 6. Study Population Live born deliveries among women aged 15-45 years between Jan 1, 2001 and Dec 31, 2007 Availability of valid gestational length in linked birth certificate Continuous enrollment and pharmacy benefit, 100 days before pregnancy through delivery
  • 7. Gestational Length Algorithm based on Health Plan DataICD-9-CM code Definition Algorithm-derived gestational length Weeks Days765.21 Less than 24 completed weeks of gestation 24 168765.22 24 weeks of gestation765.23 25-26 weeks of gestation 26 182765.24 27-28 weeks of gestation 28 196765.0-765.09 Extreme immaturity765.25 29-30 weeks of gestation 30 210765.26 31-32 weeks of gestation 32 224765.27 33-34 weeks of gestation 34 238765.28 35-36 weeks of gestation 36 252765.1-765.19 Other preterm infants765.20 Preterm with unspecified weeks of gestation 35 245644.21 Onset of delivery before 37 completed weeks of gestationGestational length for deliveries without an ICD-9-CM code for preterm birth in the table was assumed to be270 days.
  • 8. “Gold Standard” Gestational Length Birth certificate  last menstrual period (LMP)  clinical estimate (CE) / obstetric estimate (OE) CDC’s National Center for Health Statistics (NCHS) approach  LMP primarily  CE/OE, when LMP not  available  20-45 weeks (adapted from NCHS)  compatible with birth weight
  • 9. Medication ExposureDispensing dates + days supplied ; 14-day graceperiodLong term Short termChronic Acute usebasis Antidepressant Antibiotics s Amoxicillin Fluoxetine Azithromyci Sertraline n
  • 10. Statistical Analysis Mean, range, proportion of term/preterm deliveries Deliveries with two gestational lengths differ within 0, ±1, ±2, ±3, ±4, or greater than ±4 weeks (stratified by plurality) Prenatal medication exposure  Sensitivity, specificity, PPV, NPV  Any time in pregnancy or by trimester  Stratified by term/preterm determined by the algorithm
  • 11. Study Results Infants’ birth certificate files linked to health plan data in 92% deliveries Gestational age missing/invalid in linked birth certificates in 0.4% deliveries Final study population included 225,384 deliveries
  • 12. Discussion Algorithm underestimated gestational length by average 5.5 days  Restricted to singleton deliveries (86% term)  270-day upper bound  Not in multiple-gestation deliveries (36% term)  ICD-9-CM codes for preterm births Algorithm underestimated prevalence of preterm deliveries  15% in study population > 12% nationally  More women aged >35 years (21% vs. 14%)
  • 13. Discussion Algorithm correctly classified the antidepressants and antibiotics exposure status in most women  Specificity and NPV close to 100%  Poorer sensitivity and PPV for antibiotics (sporadic) vs. antidepressants (chronic)  Overestimate on antibiotics due to 14-day grace period for dispensings
  • 14. Discussion Strengths  Study population geographically and demographically diverse, increasing generalizability  Reasonable gold standard of gestational length for majority of study population Limitations  Only evaluated 1 algorithm  Only evaluated 2 antidepressants and 2 antibiotics, unknown for other medications  Medication dispensed =?= medication use
  • 15. Conclusion Gestational length algorithm based on health plan data (delivery date + preterm birth diagnosis) classified prenatal medication use well Performance slightly poorer for short-term drugs (e.g. antibiotic)
  • 16. Thank you!Questions?
  • 17. EXTRA SLIDES