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—I thank Dr Norman for his thoughtful note and suggestion to use urine analysis of MMA by gas chromatography mass spectrometry as an appropriate means for early detection of vitamin B12 deficiency in patients. This test is a 24-hour collection of urine which is refrigerated and from which a 25-mL aliquot of urine is withdrawn and frozen for shipment to a laboratory for analysis. The cost of the test in Atlanta, Ga, at the Piedmont Hospital Laboratory is $182; at the SmithKline Beecham Laboratory, the cost is $139. Both laboratories said that specimens are "sent out" to be analyzed for this test. This cost is considerably more than the $50 quoted by Norman. I do not know the reason for the differences in cost, and I do not know the cost of the serum analysis.
Upshaw CB. Urinary Methylmalonic Acid to Detect Vitamin B12 Deficiency-Reply. JAMA. 1995;273(18):1420. doi:10.1001/jama.1995.03520420032027