Can a Platelet Flag Prevent Misdiagnosis? A Report of Two Different Platelet Counts by Two Different Cell Counters for a Patient

Background: As platelet count is one of the valuable laboratory tests for disease diagnosis, its errors, such as the upper discrimination for the platelet volume distribution (PU) flag, could cause problems and misdiagnosis. Blood cell histogram evaluation can come close to overcoming the limitations of the platelet counting test. Case Report: In this study, a 36-year-old thalassemia minor male presented with the symptoms of fever and myalgia. Petechiae and purpura were observed in the patient’s lower extremities in the physical examination. Nihon Kohden Celltac G and Sysmex XP-300 cell counters were used to report the platelet count, which was reported to be 10000/μL and 129000/μL, respectively. However, the peripheral blood smear (PBS) assessment confirmed that the result of the Sysmex XP-300 cell counter was wrong, and a platelet flag was seen. This situation can be corrected by the complete blood count (CBC) histogram and PBS evaluation. Discussion: Sysmex XP-300 cell counter’s inability to differentiate severely microcytic cells from platelets can cause the PU error, which means the severe microcytic red blood cells (RBCs) were counted as platelets, causing the platelet count to be reported higher than the actual number for this patient. The PU flag means the platelet histogram intersects the PU line without touching the zero baselines, which occur in conditions such as platelet clumps, giant platelets, microcytic, and fragmented or dysplastic RBCs. In the Nihon Kohden Celltac G cell counter, this error was prevented due to the change in the PU line, and the patient’s actual platelet count was reported. To avoid such errors, abnormal platelet counts should always be confirmed with the findings of PBS. Conclusion: Poikilocytosis, such as microcytic RBCs and, can cause the PU flag, so platelet and erythrocyte histograms and PBS evaluation should be assessed.