FELINE HEINZ BODIES INTERFERENCE ON COMPLETE BLOOD COUNT USING SIEMENS ADVIA 2120: A DESCRIPTION OF TWO CASES

Introduction: Heinz bodies (HBs) in erythrocytes are a frequent finding in cats. Larger or multiple HBs can be related to haemolytic anaemia, mainly due to a severe oxidative damage. In these cases, an elevated number of circulating HBs can affect the results of laser haematology analysers, however veterinary literature on this topic is lacking. The purpose of this study was to report two cases of feline HBs detection significantly affecting complete blood count (CBC). Methods: EDTA blood samples collected from two cats affected by acute oxidative drug toxicity (case A) and diabetic ketoacidosis (case B) were processed on a routine basis at a veterinary clinical pathology laboratory. Blood samples were analysed using ADVIA 2120. Blood smears were stained with Romanovsky and new methylene blue staining and microscopically examined. HBs and white blood cell (WBC) concentrations were manually estimated. Results: Basophil/lobularity WBC count (BASO, cells/μL), peroxidase staining WBC count (PEROX, cells/μL), and ΔBASO-PEROX were 549240, 56160 and 493080 in case A, and 15680, 11430 and 4250 in case B, respectively. The WBC microscopic estimation on the blood smear confirms the PEROX results in both cases. Measured haemoglobin concentration (mHGB, g/dL), cellular haemoglobin concentration (cHGB, g/dL), and ΔmHGB-cHGB were 15.8, 9.4, and 6.4 in case A, and 10.7, 9.2, and 1.5 in case B, respectively. Mean corpuscular haemoglobin concentration (MCHC, g/dL), cellular haemoglobin concentration mean (CHCM, g/dL) and ΔMCHC-CHCM were 55.3, 33.0, and 22.3 in case A, and 41.9, 36.1, and 5.8 in case B, respectively. HBs estimation on blood smear was 950/1000 cells in case A and 200/1000 in case B. A cluster of cells lying at the bottom threshold of BASO cytogram, losing the typical configuration, was observed in both cases. These artefacts gradually disappeared during the follow-up, in agreement with the reduction of HBs number. Conclusions: An elevated number of HBs in feline erythrocytes significantly affects haematological results of ADVIA 2120, in particular relatively to the WBC count and haemoglobin indices. However, a careful interpretation of the indices and cytograms, combined with the blood smear examination, allows to obtain accurate results.