Comparison of Platelet Count Assessment: Automated Haematology Analyzer Versus Manual Peripheral Blood Smear Examination in Thrombocytopenic Patients
DOI:
https://doi.org/10.21276/apalm.3917Keywords:
thrombocytopenia, platelet count, automated haematology analyzer, peripheral blood smear, inter-observer variabilityAbstract
Background: Accurate platelet enumeration is critical in thrombocytopenia. Automated haematology analyzers provide rapid, reproducible counts but may be affected by platelet clumping, giant platelets, or abnormal platelet distribution. Manual peripheral blood smear (PBS) examination remains essential laboratory practice in assessment of severe thrombocytopenia and analyser-flagged cases.Methods: This prospective analytical study was conducted in the Haematology section of the Central Diagnostic Laboratory, Father Muller Medical College Hospital, over six months. A total of 140 thrombocytopenic samples (platelet count <150,000/cumm) were analyzed using the Sysmex XN-1000 automated analyzer and Leishman-stained PBS examination. Manual counts were performed independently by three observers: a laboratory technician, pathology postgraduate trainee and consultant pathologist. Pearson correlation, Bland–Altman analysis with proportional-bias assessment, intraclass correlation coefficient (ICC) and repeated-measures ANOVA were used.
Results: The mean automated platelet count was 64,671 ± 29,393/cumm, compared with a mean manual count of 67,755 ± 31,537/cumm. Automated and mean manual counts showed strong correlation (r = 0.962, p < 0.001). Bland–Altman analysis showed automated analyzer underestimation, with significant proportional bias for Observers 1 and 3. ICC values demonstrated excellent agreement (single-measures ICC 0.892–0.937; average-measures ICC 0.943–0.967; p < 0.001). Manual inter-observer variability was significant (p < 0.001), especially at platelet counts ≤20,000/cumm, where mean coefficient of variation was 23.93% and single-measures ICC declined to 0.743. Analyzer platelet flags occurred in 44.3% of cases, but concordance with PBS was 9.3%.
Conclusion: Automated analyzers provide reliable platelet counts but may underestimate values. Manual PBS review, preferably with consensus or repeated readings, remains essential in severe thrombocytopenia, analyzer-flagged samples and counts near transfusion thresholds.
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