Clinical utilization of the neonatal hair test for cocaine: a four-year experience in Toronto.

BACKGROUND

There has been a steady increase in the number of newborns affected by maternal drug use. Cocaine and its metabolites cross the placenta and have been routinely measured in neonatal urine; however, due to the short half-life of the drug many exposed fetuses have negative urine tests. We have developed a neonatal hair test for measuring cocaine and its metabolites by radioimmunoassay. Since the validation of this test we prospectively evaluated its clinical utility by physicians, hospital nurseries and social welfare agencies who requested neonatal hair analysis to verify clinical suspicion of maternal cocaine use during pregnancy.

OBJECTIVE

The objective of the present research was to establish the sensitivity of the hair test in validating clinical suspicion of in utero exposure to cocaine in the presence of negative urine test.

HYPOTHESIS

We hypothesized that the use of the hair test in cases of clinical suspicion but negative urine test will yield a substantially higher rate of positivity than expected in the general population.

DESIGN

Between October 1991 and April 1995 we prospectively analyzed a total of 192 neonatal hair samples to confirm clinical suspicions of intrauterine exposure to cocaine. Of these, 10 did not have sufficient hair to analyze for cocaine metabolites.

RESULTS AND DISCUSSION

Fifty-five (30%) of the remaining 182 were positive for cocaine metabolite. This rate was 5.5-fold higher than the 5.5% found by us in a population-based research study in three nurseries in Toronto (p < 0.001), thus documenting the efficiency of this test in confirming clinical suspicions of fetal exposure to cocaine. Benzoylecgonine concentrations in this cohort were 2-fold higher than among positive cases in a previous population-based screening study (p = 0.0001) indicating that when clinical suspicions prompted physicians to test neonatal hair, they identify a subgroup of heavy cocaine users, who are probably at higher perinatal risks.