Agreement between maternal cannabis use during pregnancy according to self-report and urinalysis in a population-based cohort: the Generation R Study.
OBJECTIVE
To verify self-reported information on prenatal drug use in urine because reporting in pregnancy is sensitive to stigma and might lead to misclassification.


METHODS
Using semiquantitative immunochemical analysis, the presence of the urinary metabolite (11-nor-Δ9-tetrahydrocannabinol- 9-carboxylic acid) was compared to self-reported prenatal cannabis use. Sensitivity and specificity for self-report and urinalysis outcomes were calculated and Yule's Y was used as an agreement measure.


RESULTS
Urine samples were available for 3,997 pregnant women. Of these women, 92 reported having used cannabis during pregnancy (2.3%) and 71 had positive urine screens (1.8%). In total 35% of the 92 women with self-reported cannabis use also had a positive urine screen. Positive urines were relatively frequent in women reporting cannabis use before pregnancy only (7.6%) and in women with missing information (2.6%). Sensitivity and specificity of urinalysis compared to self-report were 0.46 and 0.98. Sensitivity and specificity of self-report compared to urinalysis were 0.36 and 0.99. Yule's Y amounted to 0.77, indicating substantial agreement between the measures.


CONCLUSIONS
Our findings illustrate the difficulties in obtaining valid information on prenatal cannabis use. To improve the quality of cannabis use data, we suggest a 2-step approach starting with self-report.
The Generation R Study Group, Erasmus Medical Centre Rotterdam, Rotterdam, The Netherlands. h.marrounel@erasmusmc.nl
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El Marroun
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Tiemeier
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Hofman
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Verhulst
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D000328:Adult; D013759:Dronabinol / Q000031:analogs & derivatives / Q000652:urine; D005260:Female; D006801:Humans; D002189:Marijuana Abuse / Q000523:psychology* / Q000652:urine; D011247:Pregnancy; D011248:Pregnancy Complications / Q000523:psychology* / Q000652:urine; D057566:Self Report; D012680:Sensitivity and Specificity; D015813:Substance Abuse Detection / Q000379:methods*; D011795:Surveys and Questionnaires
C016780:11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid; D013759:Dronabinol