Comparison of Rapid Centrifugation Technique with Conventional Centrifugation for Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) Testing

Prothrombin Time (PT) and activated partial thromboplastin time (APTT) are frequently performed coagulation tests in patients with coagulation disorders especially in critical care areas and in monitoring patients on anticoagulation therapy. In coagulation testing, sample processing especially centrifugation is one of the most critical steps that affect turnaround time(TAT). This study was carried out over a period of 1year. Three hundred paired samples from patients sent for PT and APTT estimation were included. One sample was centrifuged in a regular bench top centrifuge at 1500g for 20min. The other sample was divided into two polypropylene aliquots and centrifuged in a microcentrifuge at 13000g for 3min. The plasma obtained from both methods was tested for PT and APTT using the automated method on STA Compact coagulometer (Stago) using commercial thromboplastin STA(R)-Neoplastine(R) C1 Plus and phospholipid (cephalin), STA(R)-C K PRESTR 5 respectively. Data were analyzed using descriptive statistics, Student t test, correlation coefficient and Bland-Altman plots. Mean PT, INR and APTT forboth centrifugation methods was comparable with no statistically significant difference (p>0.05). PT, INR and APTT also showed good correlation (r>0.98) when compared between the two methods of centrifugation. Bland-Altman comparison between rapid and conventional methods of centrifugation for PT, INR and APTT also showed acceptable agreement. Rapid centrifugation technique for routine coagulation testing can be used safely with a significant reduction in the TAT. This can benefit patients in critical care settings and those on outpatient oral anticoagulant therapy.