Establishment of a reference interval for thiamine concentrations in healthy dogs and evaluation of the prevalence of absolute thiamine deficiency in critically ill dogs with and without sepsis using high-performance liquid chromatography.

OBJECTIVE: To determine the normal reference interval (RI) for thiamine concentrations in healthy dogs and investigate the prevalence of thiamine deficiency in critically ill dogs with and without sepsis. DESIGN: Prospective, observational, multicenter study, conducted between 2019 and 2021. SETTING: Two veterinary university teaching hospitals. ANIMALS: A total of 109 dogs were enrolled into 3 groups: 40 healthy dogs, 33 dogs with suspected or confirmed sepsis and evidence of tissue hypoperfusion (Doppler blood pressure ≤90 mm Hg or plasma lactate ≥3 mmol/L), and 36 dogs with other critical illnesses and evidence of tissue hypoperfusion. INTERVENTIONS: For each dog, CBC, serum biochemistry, plasma lactate concentration, whole-blood thiamine concentration, blood pressure, vital parameters, Acute Patient Physiologic and Laboratory Evaluation (APPLE)fast score, and clinical outcomes were recorded, alongside basic patient parameters and dietary history. Whole-blood thiamine pyrophosphate (TPP) concentrations were measured using high-performance liquid chromatography. MEASUREMENTS AND MAIN RESULTS: The RI for whole-blood TPP in healthy dogs was 70.9-135.3 µg/L. Median TPP concentrations were significantly lower in septic dogs compared to healthy controls (P = 0.036). No significant difference in median TPP concentrations was found between septic dogs and nonseptic critically ill dogs, or between healthy dogs and nonseptic critically ill dogs. TPP concentrations were below the normal RI in 27.3% of septic dogs, compared to 19.4% of nonseptic critically ill dogs (P = 0.57). No correlations were found between TPP concentrations and lactate concentrations, age, body condition scores, time since last meal, RBC count, serum alanine aminotransferase, APPLEfast scores, or patient outcomes. CONCLUSIONS: TPP concentrations were significantly lower in septic dogs compared to healthy controls, with an absolute thiamine deficiency found in 27.3% of septic dogs. The established TPP RI allows for further investigation of thiamine deficiency in critically ill dogs.