Effect of varying storage time and temperature on unspun blood samples for prothrombin time and activated partial thromboplastin time in a tertiary hospital laboratory in the tropics

Introduction: Delays in the time of analysis of unspun blood samples stored at varying temperatures received in the laboratory pose a risk for unreliable prothrombin time (PT) and activated partial thromboplastin time (APTT) result; hence, consequent detrimental effect on patient care. This study's aim was thus to determine the optimal storage conditions and the potential effect of various storage times and temperatures on unspun samples for PT and APTT for a reliable test result. Materials and Methods: In a cross-sectional study, 33 eligible apparent healthy volunteers were recruited. Eighteen milliliters (ml) of venous blood were collected into 20 ml plastic bottles containing 2 ml of 0.109 M sodium citrate as an anticoagulant. Each citrated sample was separated into nine 2 ml aliquots. Baseline PT and APTT were determined with a coagulometer immediately and the remaining aliquots were analyzed after 3, 6, 12, and 24 h storage time at refrigerated (4°C) and room temperature (RT), respectively. The Statistical Package for the Social Sciences and Paired student t-test were used for statistical analysis. Results: At 24 h storage time at both RT and 4°C for PT, there was a statistically significant difference (P = 0.000). For APTT, a statistically significant difference was observed at 12 h (P = 0.009) and 24 h (P = 0.000) at RT whereas, at 4°C, all storage time had a statistically significant difference (P < 0.05). Conclusion: Unspun blood samples can be stored maximally for 12 h at RT and 4°C for PT whereas it is 6 h at RT only for APTT.