High-throughput urine screening for Smith-Lemli-Opitz syndrome and cerebrotendinous xanthomatosis using negative electrospray tandem mass spectrometry.

BACKGROUND: Smith-Lemli-Opitz syndrome (SLOS) and cerebrotendinous xanthomatosis (CTX) are disorders affecting cholesterol metabolism. Currently, diagnosis relies on clinical recognition and specific and complex biochemical testing.
METHODS: A rapid, high-throughput urine test, suitable for mass screening for these two disorders, was developed using flow injection negative electrospray tandem mass spectrometry with multiple reaction monitoring. Cholestane-pentol glucuronide, a known marker for CTX, was measured and a steroid sulfate with a proposed keto-pregnadien-diol structure was identified and measured for SLOS. Measurement of the two markers was readily incorporated into an existing tandem mass spectrometry method for diagnosing inborn errors of amino and organic acid metabolism.
RESULTS: Levels in affected patients were well separated from 1738 controls, ranging from 6.7 to 100 times the 99.7th percentile of controls in SLOS patients (n=3) and 7.3 to 24 times the 99.7th percentile of controls in CTX patients (n=4).
CONCLUSIONS: The addition of testing for SLOS and CTX to a routine tandem mass spectrometry urine screening program simplifies the diagnosis of these two disorders and further extends the range of inborn errors of metabolism detected by this technique.