Hair Analysis Panel Discussion: Section 6.4

Section 6
6.4 Recommendations

Panelists' recommendations focused on measures to standardize sampling protocols. The group agreed that such efforts would improve the overall usability and reliability of testing data. The group discussed sample collection, handling, and processing procedures. One panelist recommended considering hair analysis results only if the laboratory documents good practice in terms of handling and validation protocols (MK). It was also recommended that the governmental, commercial, and research laboratories pool their experience and help develop standard protocols (SS). Panelists offered the following specific recommendations:

• Standardize sample collection procedures. Samples should be ordered by a physician, taken for a defined reason, properly collected, and dealt with according to proper chain of custody procedures. A determination needs to be made regarding the best location on and distance from the scalp to test. No consensus was reached on the preferred cutting device. To avoid metal contamination, some panelists recommend using quartz or plastic or teflon-coated shears. Others questioned whether it really made that much of a difference. Most important, everyone agreed, is for the laboratory to demonstrate the extent of contamination introduced, if any, during sample collection. Lastly, sample handling (chain of custody) procedures should be the same as those applied to other environmental samples.
  
  
• Collect exposure histories. Several panelists recommended obtaining exposure histories concurrent with collecting hair samples. Information should be collected for the year prior to the collection date, although one panelist pointed out that recall bias may likely be a limiting factor. Histories should consider environmental and treatment exposures. It was recommended that the questionnaire that has been used by CDC be used as a starting point or model. Lastly, any such questionnaire should be substance-specific.
  
  
• Establish quality assurance protocols. Use quality assurance methods for laboratory analyses recommended by the World Health Organization (1994). Specifically, (1) reference samples of the same matrix (hair) with known concentrations of the metal should be used as standards, (2) reference samples should contain the metal at approximately the same concentration as the sample, (3) if such reference materials are not available, analysis of quality-control samples at different laboratories by different analytical methods must be used, and (4) because results may vary over time and for different metals, results should be present for the corresponding time periods and metals (SS).
  
  
• Require external validation. Require performance evaluations of hair testing laboratories in the form of proficiency testing (e.g., running reference samples and evaluation of materials of unknown content). The Center for Toxicology in Quebec occasionally offers a hair analysis sample for ICP-MS (DP).
  
  
• Require documentation. Testing laboratories need to be challenged to make a deliberate day-to-day effort to demonstrate internal and external validation. Calibration and quality assurance methods need to be well-documented (DP, MK).
  
  
• Encourage targeted analyses. Target testing to the specific element of interest. Testing for multiple analytes increases uncertainty. Overlapping peaks may lead to the misinterpretation of results (MK).
  
  
• Develop washing protocols. Differing opinions were voiced regarding whether hair samples should be washed, but the panelists generally agreed that the effects of washing, when performed, need to be clearly documented by the laboratory. Individual panelist input is summarized below.
  
  
• The determination of whether or not to wash the sample is a substance-specific decision (SS).
• Insufficient data exist to measure the true effects of washing, so washing adds another layer of uncertainty when data are interpreted (MK).
• One panelist recommended examining the wash solution when washing (RB), but others questioned how to interpret the resulting data, fearing that it may add yet another layer of uncertainty (DP, MK).

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