K2EDTA vs K3EDTA Stability in Yemen: Sysmex KX-21N Performance in Tropical Lab

Background: Preanalytical variability in haematological testing due to anticoagulant choice remains poorly characterized in resource-limited tropical settings. Objectives: To compare K2EDTA and K3EDTA effects on CBC parameters in Yemeni laboratories as a model for resource-limited tropical settings. Methods: We conducted a prospective study of 100 venous blood samples from healthy adult male volunteers in Ad'Dla Governorate, Yemen, between January and March 2025. Samples were collected in duplicate using K2EDTA and K3EDTA tubes, analysed using a Sysmex KX-21N haematology analyser at baseline (T0) and after six hours of storage at 22 ± 2℃ (T6). Data were analysed using repeated-measures ANOVA and paired t-tests. Results: Fresh samples showed high inter-anticoagulant concordance (ICC > 0.90). After 6-hour storage, K2EDTA exhibited significant MCV reduction (Δ = -2.33 FL, p < 0.001), while K3EDTA showed greater RBC instability (Δ = -0.16 × 1012/L, p = 0.008). Platelet activation markers increased in both anticoagulants (p < 0.01). A novel bidirectional RDW-SD pattern emerged: K2EDTA increased values (+1.71%) while K3EDTA decreased them (-2.20%, both p < 0.01). Conclusion: K2EDTA demonstrates superior stability for delayed processing (> 2 hours), while K3EDTA is preferable for immediate analysis. What This Study Adds": First Yemeni data demonstrating K2EDTA’s superior stability for delayed processing in tropical climates, supporting WHO standardization efforts. These findings support protocol adjustments for African and Middle Eastern laboratories.