Interpretation of the trace metal analysis profile for patients occupationally exposed to metals.

Trace element profile analysis detects and quantifies the presence of several metals simultaneously at low concentrations in the body. In occupational medicine, it may be used to monitor exposure or to evaluate suspected toxicity. Clinical interpretation is often difficult because, with the exception of lead and possibly cadmium, there is little firm information on toxicity thresholds. For these tests, the reference ranges typically reflect low levels of exposure in the general population and it is expected that workers handling metals in occupations such as welding and industries such as steelmaking will have higher levels. Interpretation requires some knowledge of the toxicokinetics of the metal of interest and the preferred medium for analysis for each: serum, whole blood or urine (preferably 24-hour collection). Trends are often more informative than concentrations at one time. Trace element values are reported together with a reference range which must be distinguished from the normal range of other clinical tests. As a practical matter, the greatest interpretation problems tend to be found with manganese because serum levels have a poor correlation with both recent exposure and neurological symptoms. Molybdenum and vanadium are often found to be elevated among workers exposed to metals who show no evidence of clinical illness. Interpretation of the trace element profile analysis overall when an elevation occurs generally requires close attention to the pattern of elevation, clinical context, absolute and relative magnitude of the elevation and knowledge of the exposure history.