Hair Analysis Panel Discussion: Section 3.0
Sampling And Analytical Methods
Panel discussions related to the sampling, handling, and laboratory
methodologies used in hair analysis centered around the strengths
and weaknesses of existing procedures and the lack of standardized
methods for collecting and analyzing hair samples and reporting
The group generally agreed that the technology exists to measure substances in hair, but variations in sample collection, preparation, and analytical methods can drive what will be measured in the final analysis. Therefore, the panelists encouraged the development of standard protocols for hair analysis to help ensure the generation of reliable and reproducible analytical results. In the interim, panelists encouraged laboratories to clearly document procedures used in their analyses, and encouraged users to be cognizant of these procedures when interpreting results. The group acknowledged that even if standard protocols were in place, the greatest challenge would still be interpreting the results from a practical and toxicologic perspective (see Sections 4 and 5).
Panelist Dr. Dan Paschal, research chemist at CDC, opened discussions on this topic with a brief overview of the advantages and limitations of existing analytical methods and approaches related to hair analysis. He emphasized that hair has real advantages in that (1) it can contain relatively high levels of hazardous substances of potential interest, including elements and some organic compounds, (2) it is easy to collect by relatively non-invasive methods, and (3) it is a stable specimen. He also commented on some of the limitations: lack of precision and accuracy of hair analysis results, external contamination, interindividual variations, lack of correlation with health effects, and lack of believable reference intervals.
In setting the stage for discussions on analytical methods, Dr. Paschal commented on published work related to reference intervals, detection limits, and hair concentrations of metals as a function of age (DiPietro et al. 1989; Paschal et al. 1989). His specific comments are integrated in the sections that follow.