Holotranscobalamin - a sensitive marker of cobalamin malabsorption

Background No simple and reliable method of identifying patients with cobal amin malabsorption is available at present. The measurement of plasma holot ranscobalamin, i.e. the metabolically active cobalamins bound to the transp ort protein transcobalamin, has been suggested as a means of fulfilling suc h criteria. Design We describe a method that directly quantifies cobalamins attached to transcobalamin. The method is evaluated in patients referred for gastroint estinal examination because of suspected cobalamin malabsorption. Results Of the 101 patients referred, all 48 with gastrointestinal conditio ns compatible with cobalamin malabsorption had plasma holotranscobalamin be low 35 pmol L-1 (interval of 35-160 pmol L-1). None of the patients with pl asma holotranscobalamin above the lower reference limit had conditions comp atible with cobalamin malabsorption. Conclusion The values obtained for plasma holotranscobalamin showed a bette r correlation with possible malabsorption than the values obtained for plas ma cobalamins. The specificity of the test, however, needs to be elucidated further.