Comparison of umbilical cord tissue and meconium for the confirmation of in utero drug exposure.

OBJECTIVES: Drug screening in neonates is traditionally performed using meconium, but cord tissue has been proposed as an alternative specimen. This study compares the detection of drugs in a large number of paired meconium and umbilical cord tissue samples from subjects at risk of in utero drug exposure.

DESIGN AND METHODS: Physician-ordered toxicology results and clinical information were collected in a retrospective review of subject medical records. All toxicology testing was performed by a national reference laboratory using a combination of immunoassays and chromatography-mass spectrometry. The comparison was limited to drugs present in both cord and meconium panels.

RESULTS: Overall agreement between cord and meconium ranged from 76% (cannabinoids) to 100% (barbiturates), but Cohen's kappa was <65% for 5 of the 6 drug classes we studied. Considering meconium as the gold standard, cord was less sensitive for the detection of 5 of the 6 drug classes, and for the detection of all 5 individual opioids. For 3 of the 5 individual opioids, the concentration of drug measured in meconium did not correlate well with qualitative detection in cord.

CONCLUSIONS: This study reveals different sensitivities of drug detection in umbilical cord tissue and meconium. For the drugs studied here, meconium provides greater sensitivity, and is likely to remain the specimen of choice when sensitivity is of greatest importance. These results can help clinicians, laboratorians, and epidemiologists to (1) select the most appropriate test to confirm a suspected drug exposure and (2) interpret discordant results when testing is performed in multiple matrices.