Role of the laboratory in diagnosis of organic acidurias.

Clinical signs and symptoms of organic acidurias are usually subtle and non-specific. Laboratory evaluation, therefore, is usually the only conclusive way to reach a definitive diagnosis. Defects of amino acid catabolism generally caused by diminished activity or complete absence of specific enzymes usually occurs at the later stages of a pathway and results in organic aciduria. Most of these acids are effectively cleared from the blood by the kidneys, resulting in their concentration in urine to exceed greatly that in serum. Therefore, the detection of increased organic acids is greatly facilitated by a urine assay. The use of dual capillary column gas chromatography should allow the unambiguous determination of all known organic aciduria. Using this method provides a cost-effective alternative to gas chromatography-mass spectrometry.