Utility of Platelet Abnormal Distribution Sign in Detecting Platelet Abnormalites and Fragmented RBCs

Soyeon Kim¹, Hoyoung Moon¹, Taekyun Kim¹, Mijeong Kim¹, Daehyun Chu^1,2, Miyoung Kim^1,2, Young-Uk Cho^1,2, Sang-Hyun Hwang^1,2, Seongsoo Jang^1,2
¹Department of Laboratory Medicine, Asan Medical Center, Seoul, South Korea²Department of Laboratory Medicine, University of Ulsan Colleage of Medicine, Seoul, South Korea

Introduction: The ‘Platelet Clump’ flag is a commonly used platelet flag for the detection of platelet clumps in XN instruments (Sysmex, Kobe, Japan), but shows false negativity. In this study, we evaluated the usefulness of ‘Platelet Abnormal Distribution’ sign in detection of platelet clump, giant platelet, and fragmented RBCs for the first time. Method: Platelet count was measured in a total of 3,097,285 samples using PLT-I mode on XN-20 (Sysmex) from March 2022 to Jan 2024 to evaluate frequencies of the ‘Platelet Clump’ flag (named PC) and the ‘Platelet Abnormal Distribution’ sign (named PAD). The threshold for the PC was a Q-value ≥100 in our institution. The PAD was present when PL%, PU%, PDW, MPV, and P-LCR met certain criteria in samples with platelet counts less than 100×10^3 /uL. The microscopic examination of 1500 samples measured from Jan 14 2024 to Jan 18 2024 was performed to evaluate the performance of PC and PAD. Result: The frequency of the PC and the PAD was 2.24% and 0.08% in the total 3,097,285 samples. Among the 1500 samples which underwent the microscopic examination, 74 samples showed the PC or the PAD (4.93%): 5 showed the PC only (0.33%), 68 showed the PAD only (4.53%), and 1 showed both the PC and the PAD (0.07%). The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the PC were 9%, 99%, 99%, and 17%, respectively. The PAD was present in 9 samples with platelet clumps, giant platelets, or fragmented RBCs but without PC, showing higher sensitivity of the PAD (90%) than the PC; however, the specificity, NPV, and PPV of the PAD (96%, 99%, and 13%, respectively) were similar to those of the PC. Combining the PC and the PAD increased the PPV to 91% with comparable sensitivity, specificity, and PPV (91%, 99%, and 91%, respectively) to those of the PAD alone. Conclusion: Our study demonstrated the usefulness of PAD in detecting platelet clumps, giant platelets, or fragmented RBCs. It dramatically increased the sensitivity. Using the PAD in addition to the PC increased PPV while retaining the high sensitivity of the PAD sign and the high specificity and NPV of the PC and the PAD. False negative PAD could occur in samples with low platelet count probably due to unreliable platelet histograms, leading to the low PPV of the sole PAD.