Relationships between low serum cobalamin concentrations and methlymalonic acidemia in cats

Background: Serum cobalamin concentrations below reference range are a common consequence of gastrointestinal disease in cats. Serum cobalamin ≤ 100ng/L is associated with methylmalonic acidemia. Objectives: To determine the prevalence of cobalamin deficiency, defined by elevated serum methylmalonic acid (MMA), in cats with serum cobalamin ≤ 290ng/L, and the optimum serum cobalamin concentration to predict cobalamin deficiency in cats. Sample Set: Residual serum samples (n = 206) from cats with serum cobalamin ≤ 290ng/L. Methods: Retrospective, observational study. Serum cobalamin and folate were measured with automated assays. Serum MMA was determined by gas chromatography-mass spectrometry. Cobalamin deficiency was defined as serum MMA > 867 nmol/L. Sensitivity and specificity of serum cobalamin concentrations ≤ 290ng/L for detecting MMA > 867nmol/L were analyzed using a receiver-operator characteristic curve. Results: There was a negative correlation between serum cobalamin and MMA concentrations (Spearman's = -0.74, P < 0.0001).Theprevalence of MMA ≥ 867nmol/L in cats with serum cobalamin ≤ 290ng/L was 68.4%. Serum cobalamin ≤ 160ng/L had a 74% sensitivity and 80% specificity for detecting MMA > 867nmol/L. No significant difference in serum folate concentrations was detected between affected and unaffected cats. Conclusions and Clinical Importance: Elevated MMA concentrations, suggesting cobalamin deficiency, are common in cats with serum cobalamin ≤ 290ng/L. Cobalamin deficiency is clinically significant, and supplementation with parenteral cobalamin is recommended for cats with gastrointestinal disease and low serum cobalamin concentrations.