Prevalence of hypocobalaminaemia and hypercobalaminaemia in a referral population of cats in the UK and its relevance to clinical presentation, diagnosis and prognosis.

ObjectivesThis study aimed to assess the prevalence of hypocobalaminaemia (B12 <400 pg/ml) and hypercobalaminaemia (B12 >1000 pg/ml), describe the clinicopathological abnormalities and the diagnostic imaging findings in a referral population of cats in the UK, and identify the underlying disease processes associated with both conditions.MethodsA retrospective study of cats that had their serum cobalamin concentration assessed between December 2016 and December 2023 at a single referral hospital; 216 cats were included. Patient outcome was established from the clinical records.ResultsA total of 76 (35%) cats had hypocobalaminaemia and 67 (31%) cats had hypercobalaminaemia. The most common diagnoses were chronic enteropathy (CE) in 39/76 (51%) hypocobalaminaemic cats and 39/67 (58%) hypercobalaminaemic cats (P = 0.001), and high-grade lymphoma in 14/76 (18%) hypocobalaminaemic cats and 11/67 (16%) hypercobalaminaemic cats (P = 0.438). The most common clinical signs were chronic vomiting in 36/76 (47%) hypocobalaminaemic cats and 24/67 (36%) hypercobalaminaemic cats (P = 0.005), hyporexia in 40/76 (53%) hypocobalaminaemic cats and 21/67 (31%) hypercobalaminaemic cats (P <0.001), and chronic diarrhoea in 12/76 (16%) hypocobalaminaemic cats and 21/67 (31%) hypercobalaminaemic cats (P = 0.001). The most common abnormalities identified on abdominal ultrasound were lymphadenomegaly and thickened intestines in 49/76 (64%) hypocobalaminaemic cats and 28/67 (42%) hypercobalaminaemic cats (P = 0.0025). Median survival time was 274 days in the hypocobalaminaemic group and 711 days in the hypercobalaminaemic group (P = 0.001). The hypocobalaminaemic cats exhibited significantly reduced survival time compared with hypercobalaminaemic cats (odds ratio 2.4 vs 0.4, respectively) (P <0.001).Conclusions and relevanceThis study suggests that cobalamin has limited diagnostic utility in differentiating between underlying disease processes; chronic diarrhoea and CE are more common in hypercobalaminaemic cats in contrast with the previous literature. Hypocobalaminaemia is associated with reduced survival in this cohort of cats; therefore, early cobalamin supplementation is recommended.