Evaluation of the Validity of the Gestational Length Assumptions Based Upon Administrative Health...
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Evaluation of the Validity of a Gestational Length Algorithm Based
upon Electronic Health Plan Data
Qian Li, Susan. E. Andrade, William O. Cooper, Robert L. Davis, Sascha Dublin, Tarek A. Hammad, Pamala. A. Pawloski, Simone P. Pinheiro, Marsha A. Raebel, Pamela E. Scott, David. H. Smith, Inna Dashevsky, Katie Haffenreffer, Karin E. Johnson, Darren Toh
18th Annual HMO Research Network Conference, Seattle WA
May 2, 2012
Funding Source & Conflict of Interest
Contracts HHSF223200510012C, HHSF223200510009C, and 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
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)
Objectives
To examine the validity of a common algorithm by comparing
algorithm-derived gestational length & prevalence of medication exposures during pregnancy “gold standard” measures in birth certificates
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 - Demographics - Outpatient pharmacy dispensing - Outpatient and inpatient encounter Administrative and
Claims
- Socio-demographic (race/ethnicity) - Medical - Reproductive (parity, gestational age)
Birth Certificate
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
Gestational Length Algorithm based on Health Plan Data
ICD-9-CM code Definition Algorithm-derived gestational lengthWeeks Days
765.21 Less than 24 completed weeks of gestation24 168765.22 24 weeks of gestation
765.23 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 infants
35 245765.20 Preterm with unspecified weeks of gestation644.21 Onset of delivery before 37 completed weeks of
gestation
Gestational length for deliveries without an ICD-9-CM code for preterm birth in the table was assumed to be 270 days.
“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
Medication Exposure
Long term Chronic basis
Antidepressants
FluoxetineSertraline
Short term Acute use
Antibiotics
AmoxicillinAzithromycin
Dispensing dates + days supplied ; 14-day grace period
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
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
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%)
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
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
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)
Thank you!Questions?
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