Specimen collection: Two samples (A and B) are collected.
Validity checking of hair should include:
(1) a digestion test
(2) a microscopic examination of the hair
(3) a dye test
(4) solubility in methanol
(5) check for an unusual color
(6) compare the color and appearance of samples A and B
(7) check for a mixture of hair in the samples
(8) review of analytical results for evidence of an adulterant (failure to recover internal standards, unusual test reactions, damage to laboratory equipment)
(9) screening for and identification of an interfering substance or adulterant
A hair specimen is considered adulterated if:
(1) an adulterant is identified at a level above the threshold concentration
A hair specimen is considered invalid if:
(1) a problem is found with the hair specimen
(1a) specimen A has a different physical appearance than specimen B
(1b) there is interference with an immunoassay for drugs on two separate aliquots
(1c) there is interference with a confirmatory test on at least two separate aliquots
(1d) there is an interfering substance that may damage laboratory equipment
(2) the interfering compound is not positively identified
