Evaluation of the difference between mean corpuscular haemoglobin concentration and mean cellular haemoglobin concentration in canine complete blood count assessed with an automated haematology analyser

Objectives The study aimed (a) to establish the reference interval for Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration in healthy dogs by ADVIA 2120 haematology analyser, (b) to identify the causes of increased Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration in both healthy and diseased canine samples and (c) to establish a cut-off value to prompt further diagnostic evaluations by practitioners. Materials and Methods A retrospective study was conducted evaluating the medical records of dogs referred to a Veterinary University Hospital. Healthy dogs were prospectively included to establish reference interval for complete blood count variables comprising Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration. Complete blood count reports of dogs who had both complete blood count and biochemistry performed concurrently were included. Complete blood counts were performed within 2 hours of sample collection, and biochemical analyses were carried out on serum samples within 12 hours. The macroscopic sample alterations were retrieved, including haemolysis, icterus, lipaemia and their severity. Results Reference interval for Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration was established and ranged from −1.70 to 2.20 g/dL (90% confidence interval of the upper limit 1.92 to 2.50). The Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration was significantly increased in lipaemic and haemolytic samples and significantly correlated with their severity. The frequency of samples with increased Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration (≥2.5 g/dL) was significantly higher in lipaemic and haemolytic samples and in patients undergoing corticosteroid therapy or affected by Cushing’s syndrome. Clinical Significance An increase in Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration in dogs is often associated with macroscopic sample alterations, mainly due to lipaemia, haemolysis, or both. When a Δmean corpuscular haemoglobin concentration-mean cellular haemoglobin concentration value of >2.5 g/dL is noted, laboratories and practitioners should carefully evaluate the samples for any evidence of haemolysis or lipaemia.