DETERMINATION OF REFERENCE RANGES FOR ELEMENTS IN HUMAN SCALP HAIR

Expected values, reference ranges, or reference limits are necessary t o enable clinicians to apply analytical chemical data in the delivery of health care. Determination of references ranges is not straightforw ard in terms of either selecting a reference population or performing statistical analysis. In light of logistical, scientific, and economic obstacles, it is understandable that clinical laboratories often comb ine approaches in developing health associated reference values. A lab oratory may choose to: 1. Validate either reference ranges of other la boratories or published data from clinical research or both, through c omparison of patients test data. 2. Base the laboratory's reference va lues on statistical analysis of results from specimens assayed by the clinical reference laboratory itself. 3. Adopt standards or recommenda tions of regulatory agencies and governmental bodies. 4. Initiate popu lation studies to validate transferred reference ranges or to determin e them anew. Effects of external contamination and anecdotal informati on from clinicians may be considered. The clinical utility of hair ana lysis is well accepted for some elements. For others, it remains in th e realm of clinical investigation. This article elucidates an approach for establishment of reference ranges for elements in human scalp hai r. Observed levels of analytes from hair specimens from both our labor atory's total patient population and from a physician-defined healthy American population have been evaluated. Examination of levels of elem ents often associated with toxicity serves to exemplify the process of determining reference ranges in hair. In addition the approach serves as a model for setting reference ranges for analytes in a variety of matrices.