Meconium drug testing in multiple births in the USA

Little is published about newborn drug testing in multiple gestations. The objective of this study was to review the results of meconium drug screening in multiple births to compare drug(s) and/or drug metabolite(s) detected. A retrospective analysis was conducted using data from a national reference laboratory and an academic medical center. The data were de-identified for the reference laboratory dataset. For the academic center data, a detailed chart review of the newborn and mother's medical record was performed on cases for which one or more drug(s) and/or metabolites(s) were identified and confirmed in meconium. Meconium was analyzed for amphetamine, methamphetamine, barbiturates, benzodiazepines, cannabinoid metabolites, cocaine metabolites, methadone, opiates, oxycodone, phencyclidine and propoxyphene. One hundred and forty-two of 1,084 sets of twins and 2 of 20 sets of triplets had mismatched results. The incidence of mismatched results among the individual drug or drug classes tested was 0.9% (208 of 23,848 total results). For the panel of drug testing performed, mismatches were seen in 13% (142 of 1,084) sets of twins and 10% (2 of 20) sets of triplets. Barbiturates (33%), opiates (30%) and benzodiazepines (28%) were the most common mismatches in the national reference laboratory dataset. Benzodiazepines (89%) and opiates (51%) were most common in the academic medical center dataset with most explained by iatrogenic medications administered to one infant but not the other. Mismatches for cannabinoids most often occurred when tetrahydrocannabinol metabolites were present at a low concentration (near lower reporting limit) in one infant but not the other. Mismatched results of meconium drug testing in multiples not explainable by differences in prescribed medications are uncommon and most often occur when an analyte is barely above reporting cutoff in only one infant. Administration of iatrogenic medications to one infant but not the other(s) is another frequent cause of such mismatches.