Diagnosis Diagnosing metal toxicities can be difficult; the symptoms and consequences of many, especially chronic toxicities, are non-specific and may resemble other diseases. A careful analysis of dietary, environmental, and occupational exposure history is one of the most important tools in evaluating a potential metal toxicity (Vearrier 2010). Metal testing can be an important aid to confirm or rule out a diagnosis of metal toxicity. Some metal tests include: Blood testing. Commercial blood tests are available for many metals (universally toxic metals, such as lead and mercury, as well as essential metals that are toxic above certain thresholds, such as iron or copper). Blood levels of cadmium and lead are usually indicative of recent exposures and may not reflect whole body burdens (ATSDR 2007b; ATSDR 2012b). For example, in the case of lead, blood levels are only indicative of exposure over the previous 90 days (ATSDR 2007b). In the case of arsenic, which is cleared rapidly from the blood, blood tests may only be reliable during early stages of intoxication (< 7-10 days after exposure) (Rusyniak 2010). There is a poor correlation between blood levels and exposure for aluminum (ATSDR 2008b). Reference ranges for individual tests depend on the laboratory performing the analysis. Urine testing. Because of differences in the rates of excretion for toxic metals, urine tests are indicative of cumulative exposure/total body burden for some metals (eg, cadmium) and recent exposure for others (eg, mercury) (ATSDR 2001; ATSDR 2012b). Urinary arsenic can be elevated following seafood consumption, limiting its diagnostic value in some cases (ATSDR 2007a). Post-challenge or post-provocation urine tests, which involve the measurement of urine metal concentrations following administration of a chelator, may reveal sources of stored toxic metals. However, since there are no broadly accepted reference ranges for urine metals determined by this technique, these tests are likely of limited diagnostic value and are not validated (Vearrier 2010; American College of Medical Toxicology 2010). Reference ranges for individual tests depend on the laboratory performing the analysis. Hair and nail analysis. Hair and nail analysis can be used to determine cumulative exposure to cadmium, lead, arsenic, and methylmercury. While reliable for large body burdens, it may not be sensitive enough to resolve differences in lower exposures; it is also sensitive to external contamination (Suzuki 1989; Hughes 2006). X-ray fluorescence (XRF). XRF is a non-invasive technique for assessing tissue deposits of metals (cumulative exposure). It can be used to detect cadmium in kidneys and lead in bones (Nilsson 1995; ATSDR 2007b). XRF is not a widely available technique.
Posted on: Tue, 21 Jan 2014 05:10:51 +0000
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