SECTION 3
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 results.
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.