Nonlarge, Low Platelet Component Concentration Fraction: A Novel Platelet Component‐Based Screening Marker for Immune Thrombocytopenia

INTRODUCTION: The use of automated hematology analyzers for immune thrombocytopenia (ITP) screening has traditionally relied on platelet size-related indices, including mean platelet volume and immature platelet fraction. The ADVIA 2120i Hematology System calculates nine platelet fractions based on platelet volume (Vol) and refractive index (RI), the latter reflecting intracellular component concentration. This study evaluated the nonlarge, low platelet component concentration fraction (NL-LPLC%) as a potential ITP-specific marker. METHODS: We retrospectively analyzed 55 untreated patients with thrombocytopenia (ITP, 23; myelodysplastic syndromes [MDS], 19; aplastic anemia [AA], 13) and 34 healthy controls. The NL-LPLC% was measured and compared with the reticulated platelet fraction (RP%) and other platelet indices. RESULTS: Receiver operating characteristic curve analysis revealed that the NL-LPLC% (RI: < 1.373, Vol: < 20 fL) showed high diagnostic performance for ITP (sensitivity, 91.3%; specificity, 90.6%). In contrast, large, low component platelets (RI: < 1.373, Vol: ≥ 20 fL) showed lower sensitivity (56.5%) and specificity (65.6%). Patients with ITP had a significantly higher RP% than those with MDS and AA (p < 0.05) but a lower NL-LPLC% (p < 0.01). The NL-LPLC% and RP% showed a strong negative correlation (r = -0.72, p < 0.01). CONCLUSION: The NL-LPLC% derived from the nine platelet fractions obtained using an ADVIA 2120i Hematology System may serve as a novel screening marker for ITP, emphasizing platelet quality rather than size alone.