The relationship of serum cobalamin to methylmalonic acid concentrations and clinical variables in cats

Abstract

Background: Serum cobalamin concentration [CBL] suggests CBL deficiency in cats but serum methylmalonic acid concentration [MMA] more accurately indicates CBL deficiency. Objective: To examine the ability of [CBL] to predict CBL deficiency defined by increased [MMA], and relationships of [CBL] and [MMA] with select clinical and clinicopathological variables. Animals: One hundred sixty-three client-owned cats with [CBL] measurements, 114 cats with simultaneous [MMA] measurements; 88 cats with medical information. Methods: Prospectively collected [CBL] and [MMA] were compared using scatter plots, receiver operating characteristic and correlative analyses with historical [CBL] thresholds and those identified in the study. [CBL] and [MMA] were compared retrospectively to specific clinical and clinicopathological variables. Results: [CBL] correlated negatively with [MMA] (τ = -0.334, P 900 pg/mL and 290 pg/mL (historical thresholds). [CBL] correlated with mean corpuscular volume (τ = -0.199, P = .013) and [MMA] with hematocrit (τ = -0.28, P = .006). Conclusions and Clinical Importance: Cobalamin deficiency ([MMA] ≥ 1,343 nmol/L) occurred in 42% of cats and is predicted with high specificity by [CBL] ≤ 209 pg/mL. CBL status correlates with microcytosis and anemia. Discordance between [CBL] and [MMA] cautions against relying on any single marker for determining CBL status. © 2013 by the American College of Veterinary Internal Medicine.