Pattern of Coombs’ test reactivity has diagnostic significance in dogs with immune‐mediated haemolytic anaemia

O bjectives :To investigate the clinical significance of the pattern of Coombs’ test reactivity in dogs with immune‐mediated haemolytic anaemia.M ethods :Sixty‐five anaemic dogs with a positive Coombs’ test were included. Coombs’ testing was performed at 4 and 37°C with polyvalent canine Coombs’ reagent and antisera specific for each of canine immunoglobulin G, immunoglobulin M and complement factor C3. The impact of performing testing with only polyvalent antiserum at 37°C was assessed. Chi‐squared tests were used to compare Coombs’ test reactivity in dogs with primary immune‐mediated haemolytic anaemia (group A) and in dogs with concurrent/underlying disease (group B). Following Bonferroni correction, significance was set at P≤0·003.R esults :Eleven dogs would have been regarded as Coombs’ negative had they been tested with polyvalent antiserum at 37°C alone. Group A dogs were significantly more likely to be positive with polyvalent antiserum and/or anti‐dog immunoglobulin G at 4 and/or 37°C (P≤0·001) and tended to be less likely to be positive with anti‐dog immunoglobulin M at 4°C (P=0·040).C linical S ignificance :Testing of anaemic dogs with polyvalent Coombs’ reagent at 37°C was less sensitive than testing with monovalent reagents at 4 and 37°C. The pattern of Coombs’ test reactivity differed significantly between dogs with primary immune‐mediated haemolytic anaemia and those with concurrent/underlying disease.