Background: In this study we analysed the reliability of HPLC determinationof 2.3.5-pyrroletricarboxylic acid (PTCA). This product derives from oxidation of melanin in human hair,and is a good candidate as a risk marker for skin tumors. Material/Methods: We determined PTCA in 100melanoma cases and 100 controls, 21 replicates from six different reference hairs, two trace elements,and one reference sample (brown hair). Results: Work-up procedures showed an almost perfect reproducibilitywith an Intraclass Correlation Coefficient (ICC) of 0.990. We noticed a low, detectable, but not statisticallysignificant decrease in reproducibility proportional to the amount of PTCA. Agreement between determinationfollowing injection of the same solution in HPLC column was also high, with an overall ICC of 0.986.Simultaneous analysis of reproducibility showed a partial ICC for work-up (0.986), for injection (0.987),and an overall standardised ICC (0.975). The analysis of the two reference tracers in successive testsshowed a weak, not statistically significant, decreasing linear drift, possibly due to various factors,such as aging of chemical solutions and HPLC columns. Conclusions: PTCA extracted from human hair throughoxidation and determined with HPLC can be considered a reliable marker as a candidate for identifyingpersons at high risk for melanoma.

Keywords: Chromatography, High Pressure Liquid - standards, Hair - chemistry, Melanoma - diagnosis, Pyrroles - analysis, Reproducibility of Results, Risk