title: 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.
  
  
  METHODS
  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 < .0001). [MMA] ≥ 1,343 nmol/L identified CBL deficiency. [CBL] = 209 pg/mL optimized sensitivity (0.51), specificity (0.96), PPV (0.89), and NPV (0.74) for detecting [MMA] ≥ 1,343 nmol/L. Prevalence of CBL deficiency was 42% (48/114) when defined by [MMA] ≥ 1,343 nmol/L versus 23% (27/114) by [CBL] ≤ 209 pg/mL. Unexpectedly, 23 and 45% of 48 cats with [MMA] ≥ 1,343 nmol/L had [CBL] > 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
  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.
authors.affiliation: College of Veterinary Medicine, Cornell University, Ithaca, NY.
authors.forename: P
authors.initials: P
authors.lastname: Worhunsky
authors.forename: O
authors.initials: O
authors.lastname: Toulza
authors.forename: M
authors.initials: M
authors.lastname: Rishniw
authors.forename: N
authors.initials: N
authors.lastname: Berghoff
authors.forename: C G
authors.initials: CG
authors.lastname: Ruaux
authors.forename: J M
authors.initials: JM
authors.lastname: Steiner
authors.forename: K W
authors.initials: KW
authors.lastname: Simpson
mesh_terms: D000818:Animals; D002415:Cats / Q000097:blood* / Q000502:physiology; D003404:Creatinine / Q000097:blood; D004909:Erythrocyte Indices / Q000662:veterinary*; D006400:Hematocrit / Q000662:veterinary*; D008764:Methylmalonic Acid / Q000097:blood*; D010758:Phosphorus / Q000097:blood; D012016:Reference Values; D012680:Sensitivity and Specificity; D014805:Vitamin B 12 / Q000097:blood*
chemical_list: D010758:Phosphorus; D008764:Methylmalonic Acid; D003404:Creatinine; D014805:Vitamin B 12
keywords: Diagnostic accuracy; Enteropathy; Gastrointestinal disease; Hepatopathy; Sensitivity; Specificity; Test performance; Vitamin B12