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

AbstractIntroduction: platelet count errors such as PU flag, could cause misdiagnosis. Case report: a ۳۶-year-old thalassemia minor male with fever and myalgia presented. Petechiae and purpura in the lower extremities of patients were observed in physical examination. The platelet count was assessed by Nihon Kohden’s Celltac G cell and Sysmex XP-۳۰۰ cell counter and the platelet count was reported ۱۰,۰۰۰/μL and ۱۲۹,۰۰۰/μL respectively. But peripheral blood smear assessment confirms that the result of the Sysmex XP-۳۰۰ cell counter was wrong and a platelet flag was seen. This situation can be corrected by the CBC histogram and peripheral blood smear evaluation. Discussion: Sysmex XP-۳۰۰ cell counter inability to differentiate severely microcytic cells from platelets can cause the PU error, which means the severe microcytic RBCs were counted as platelets that cause the platelet count falsely higher than the actual number in this patient. The PU flag means the platelet histogram intersects the PU line and does not touch the zero baseline, that occur in conditions such as platelet clumps, giant platelet, microcytic and fragmented or dysplastic RBCs in hemolytic anemia. In Nihon Kohden’s Celltac G cell counter, due to the change in the PU line this error was prevented and the actual platelet count of the patient was reported. By the way, to avoid such errors, abnormal platelet counts should always be confirmed with the findings of PBS. ConclusionPoikilocytosis such as microcytic RBCs can cause the PU flag, so platelet and erythrocytes histograms and PBS evaluation should be assessed.