Laboratory evaluation for vitamin B12 deficiency: the case for cascade testing

Clin Med Res. 2013 Feb;11(1):7-15. doi: 10.3121/cmr.2012.1112. Epub 2012 Dec 21.

Abstract

Objective: Potential vitamin B(12) deficiency is a common clinical diagnostic problem, and many providers have a low threshold for initiating therapy. The goal of this study was to systematically evaluate current practice patterns regarding the laboratory evaluation of suspected vitamin B(12) deficiency.

Methods: This retrospective study reviewed the electronic medical records of 192 patients initiated on intramuscular vitamin B(12) injections.

Results: Only 12 patients had objectively documented hematologic responses: decrease of mean corpuscular volume by ≥5 fL with stable or improved hemoglobin. Another 5 patients had equivocal hematologic responses. There was one plausible neurologic response. Thus, only 18 (9.4%) of 192 patients had data supportive of a clinical response. In these 18 patients, the baseline serum B(12) level was ≤107 pg/mL; only 3 patients also had a baseline serum methylmalonic acid level, which was ≥1.29 μmol/L in all 3 patients.

Conclusions: Currently, only a small minority of patients initiated on intramuscular vitamin B(12) supplementation derive any meaningful clinical benefit. Furthermore, current testing recommendations for vitamin B(12) deficiency are usually not followed. Up-front ordering of a diagnostic testing cascade is recommended to improve compliance; an example is presented with decision points chosen to improve specificity for clinically evident vitamin B(12) deficiency without loss of sensitivity. Ultimately, a better understanding of vitamin B(12) physiology is needed to develop and evaluate laboratory tests that more accurately reflect true intracellular vitamin B(12) status.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Algorithms
  • Female
  • Hemoglobins / metabolism
  • Humans
  • Injections, Intramuscular
  • Male
  • Methylmalonic Acid / blood
  • Middle Aged
  • Retrospective Studies
  • Vitamin B 12 / administration & dosage
  • Vitamin B 12 / therapeutic use*
  • Vitamin B 12 Deficiency / blood
  • Vitamin B 12 Deficiency / diagnosis*
  • Vitamin B 12 Deficiency / drug therapy*
  • Young Adult

Substances

  • Hemoglobins
  • Methylmalonic Acid
  • Vitamin B 12