Anaemia: cobalamin deficiency: methylmalonic acid helped diagnose or exclude it.

Clinical bottom line (level 4)

  1. Methylmalonic acid levels in patients with low serum cobalamin helped diagnose (LR+11) and exclude (LR+0.036) cobalamin deficiency.
Moelby et al: Journal of Internal Medicine 1990; 228: 373-378
Expires June 2003

The study

Setting: university hospital, Denmark

42 patients (aged range 24 to 84 years, 83% female) having haematological evaluation for serum cobalamin <100 pmol/l

Independent blinded reference standard, applied in all patients from a consecutive ?appropriate spectrum.
Reference standard:
  • serum cobalamin <100 pmol/l and one of:
    • abnormal Schilling test (cobalamin excretion less than 10%)
    • megaloblastic bone marrow morphology not explained by folate deficiency
Diagnostic test: serum methylmalonic acid- positive if >0.34 µ mol/l

The evidence

pre-test probability of cobalamin deficiency: 74%, (95% CI: 61% to 87%)

diagnostic test cobalamin deficiency no deficiency LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
methylmalonic acid >0.34 µmol/l 30 1 11
(1.6 to 69) 		97% 0.036
(0.0051 to 0.25) 		9%
total 31 11

  • 57% of patients had anaemia; 47% had some evidence of neurological and neuropsychiatric symptoms.

Citation

  1. Moelby L, Rasmussen K, Jensen MK, et al: The relationship between clinically confirmed cobalamin deficiency and serum methylmalonic acid. Journal of Internal Medicine 1990; 228: 373-378
Search Terms: reference in review article
Contributor: Chris Ball and Clare Wotton, June 2000
Reviewer:

Clinical Question.
Patient having haematological evaluation for serum cobalamin <100 pmol/l
Intervention or Exposure methylmalonic acid
Comparison abnormal Schilling test
Outcome diagnosis of cobalamin deficiency