Does Platelet Contamination Really Affect the Coagulation Tests? A Prospective Study

Rajalakshmi Rajashekar, Vani Krishnamurthy, Srinivasa Murthy Doreswamy


AIM: Coagulation tests are often requested as urgent tests by the intensive care clinicians. This is one of the many tests which is grossly influenced by pre analytical errors. Platelet contains phospholipids and pro coagulants which can interfere with the coagulation results. Preparation of platelet poor plasma by centrifuging at 1500 g for 15 mins is the standard recommended procedure. In order to decrease the turnaround time, several authors have centrifuged the sample at high speeds to obtain platelet poor plasma and reported unaffected coagulation test results. However, the effect of platelet contamination on the results of the coagulation tests was less well studied.

METHODS: we prospectively analysed the coagulation test results after centrifuging at 1000 g (Standard spin) and 500 g (Intervention spin) respectively. A total of 31 samples were studied out of which, 15 had normal coagulation and 16 had abnormal coagulation results. Agreement of values between the two preparations were determined with Bland Altman analysis.

RESULTS: Median platelet count in standard spin group was 4000/cumm and with intervention spin was 25000/cumm. Estimated mean difference (95% CI) between intervention and standard spin for prothrombin time was -0.59 secs (-0.96 to -0.03), for INR was -0.059 (-0.11 to -0.001) and for activated partial thromboplastin time was -0.59 secs (-1.5 to +0.3).

CONCLUSIONS: Platelet contamination of plasma insignificantly shorten the coagulation test results and remains clinically useful.


Activated partial thromboplastin time; Coagulation tests; Platelet contamination; Prothrombin time

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