Evaluation of the peripheral blood manual smear rate in Pediatric Patients

Abstract

Haematology analyzers provide accurate and precise blood cell counts, histograms and flags. However, blood smear review is essential to identify certain pathologies. Each laboratory should establish the acceptable rate of revision considering the population characteristics to ensure quality results. The International Society of Laboratory Haematology through the International Consensus Group of Haematology Review (ICGHR) recommends smear manual review based on the reporting alarms to avoid unnecessary reviews and minimize those cases in which clinically significant abnormalities are not detected (false negatives). These rules are indicative that each laboratory should validate it for its population. Objective: The aim of the present study was to verify the review criteria proposed
by the ICGHR to assess their applicability in paediatric patients. Methods: One thousand reports of complete blood cell count of paediatric patients obtained in a Beckman-Coulter LH750 counter were analyzed. Smears of all samples were stained and microscopic review was performed. We found that 64.7 % of the reports analyzed presented at least one of the criteria proposed by the ICGHR, 35.9 % were false positive, and the rate of false negative was 2.8 %: 46.4 % corresponded to erythrocyte morphology, 39.3 % to platelet morphology, 17.8 % to left shift and 17.8 % to atypical lymphocytes. In some of these samples, more than one alteration was detected. Given that an acceptable rate of false negative (<5%) was obtained, we conclude that the rules proposed by the ICGHR are applicable in our laboratory.