Analysis of pubic hair as an alternative specimen to scalp hair: a contamination issue.

ABSTRACT

Pubic hair is often analyzed as an alternative to scalp hair to prove previous drug use. However, urine is a potential source of external contamination. In the present study, the concentrations of methamphetamine (MA) and amphetamine (AP) in both scalp and pubic hair from illegal MA users were compared. Furthermore, in order to investigate the external contamination of pubic hair by urine, MA and AP absorbed into pubic hair that had been contaminated with authentic urine from a MA user were measured using a previously validated method. The effect of shampoo-wash on the contaminated pubic hair was also examined. However, no correlation was found in the MA and AP concentrations between scalp and pubic hair from illegal MA users. As the number of contamination events by authentic urine increased, the concentrations of MA and AP in pubic hair increased. Both MA and AP were detected in the first methanol washes of the contaminated hair samples but were not detected in the second methanol washes. As the number of shampoo-washes of the contaminated pubic hair increased, the concentrations of MA and AP gradually decreased. Even though pubic hair can be used as an alternative to scalp hair to prove previous drug use, it should be avoided when estimating drug use history. It should be also noted that higher quantitative results in pubic hair do not necessarily represent heavier drug use.