Isotope-dilution assay for urinary methylmalonic acid in the diagnosis of vitamin B12 deficiency. A prospective clinical evaluation.

Journal Article (Journal Article)

Vitamin B12 deficiency is a frequently considered diagnosis for which there is no single, commonly available and accurate test. A urinary methylmalonic acid assay using gas chromatography-mass spectrometry has been proposed as the preferred test. We reviewed vitamin B12 assays on 1599 consecutive patients and prospectively studied all patients with low serum B12 levels (n = 75) and a random sample of patients with normal levels (n = 68). Of 96 evaluable patients, 7 had clinical deficiency. All 7 deficient patients had urinary methylmalonic acid levels greater than 5 micrograms/mg creatine (sensitivity, 100%; confidence interval, 65% to 100%). Of the 89 patients who were not clinically deficient, 88 had urinary methylmalonic acid levels less than or equal to 5 micrograms/mg creatinine (specificity, 99%). The overall test accuracy in this population was 99%. If the high sensitivity and specificity of the gas chromatography-mass spectrometry assay for urinary methylmalonic acid is supported by other clinical studies, the methylmalonic acid assay may become the reference standard for the diagnosis of vitamin B12 deficiency.

Full Text

Duke Authors

Cited Authors

  • Matchar, DB; Feussner, JR; Millington, DS; Wilkinson, RH; Watson, DJ; Gale, D

Published Date

  • May 1987

Published In

Volume / Issue

  • 106 / 5

Start / End Page

  • 707 - 710

PubMed ID

  • 3551712

International Standard Serial Number (ISSN)

  • 0003-4819

Digital Object Identifier (DOI)

  • 10.7326/0003-4819-106-5-707


  • eng

Conference Location

  • United States