Table 5.

Comparison of microscopic hair characteristics between false positives and true negatives.

	False pos	True neg	P value
Number of fibres analysed	2274	2718
Percentage of samples with at least one medullated fibre	71.8%	58.1%
Average no. of medullated fibres per sample	2.1	1.5	<0.0001
Percentage of samples with at least one hair displaying surface contaminants	29.0%	12.4%
Average no. of fibres with surface contaminants per sample	0.7	0.3	<0.0001
Mean diameter < 55	72	69	0.129
Mean diameter > 65	71	65	0.161