Erroneous Automated WBC Differentials—A Case Series

Abstract

Background and Aims: Peroxidase deficiency is one of the commonly inherited phagocytic defects. It has been also found to exist as a transient phenomenon in association with some clinical conditions. But that it can interfere and cause erroneous automated differential WBC count is something which is not commonly known. Materials and methods: Complete blood counts were analysed using Advia 2120i and Coulter DXH 900 haematology analysers and manually reviewed on peripheral blood smear stained with Leishman stain. Results: Peroxidase deficiency in neutrophils and eosinophils resulted in them getting counted as monocytes by the analyser causing pseudomonocytosis, pseudoneutropenia and pseudoeosinopenia. These were detected by a slide review and by reanalysing the samples on an analyser which worked on a different principle. Conclusion: There is a need to confirm monocytosis given by analysers working on the peroxidase principle with an alternate method. This will prevent needless medical investigations for pseudoneutropenia, pseudoeosinopenia and persistent monocytosis, thus preventing unwarranted mental agony and financial burden to patients. It also helps to save the laboratory’s reputation. A careful review of instrument flags not only helps reach an accurate result but sometimes they can also aid in the diagnosis of a rare potential genetic disorder like MPO deficiency.