A team from Oakland, California assessed the reliability of data from commercial laboratories advertising multi-mineral hair analyses for nutritional or toxicity assessment. They evaluated whether the analysis has improved since a study in 1985 found poor reliability for the test.
The researchers took a split hair sample from near the scalp of a single healthy volunteer. This was submitted for analysis to 6 commercial US laboratories, which analyze 90 per cent of samples submitted for mineral analysis in the United States.
Agreement of test results for each analyte, laboratory reference ranges, laboratory characteristics, and interpretation of health implications were assessed.
Differences in highest and lowest reported mineral concentrations exceeded 10-fold.
The team found that laboratory differences in highest and lowest reported mineral concentrations, for the split sample, exceeded 10-fold for 12 minerals. Statistically significant extreme values were reported for 14 of the 31 minerals that were analyzed by 3 or more laboratories.
Variations also were found in laboratory sample preparation methods and calibration standards. Laboratory designations of normal reference ranges varied greatly, resulting in conflicting classifications (high, normal, or low) of nearly all analyzed minerals. In addition, laboratories provided conflicting dietary and nutritional supplement recommendations based on their results.
Researcher Sharon Seidel said on behalf of the group, "Hair mineral analysis from these laboratories was unreliable, and we recommend that health care practitioners refrain from using such analyses to assess individual nutritional status or suspected environmental exposures."
"Problems with the regulation and certification of these laboratories also should be addressed," she concluded.