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

Abstract

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.

Impact of rapid centrifugation on routine coagulation assays in South Africa

“…Laboratories are expected to provide accurate and reliable results within defined turn-around times (TATs) to facilitate the diagnosis, management and prognostication of patients. 1 , 2 There are ongoing attempts to improve TATs as this will directly impact patient management. 3 , 4 Coagulation assays are some of the most commonly ordered urgent and routine investigations.…”

“… 3 , 4 Coagulation assays are some of the most commonly ordered urgent and routine investigations. 1 , 2 The recommended sample preparation method for coagulation testing is the centrifugation of whole blood to obtain platelet-poor plasma (PPP), defined as plasma with a platelet count of < 10 × 10 9 /L, which minimises interference by the platelet phospholipid surface, thereby preventing the activation of clotting factors. 5 Obtaining PPP from whole blood requires the application of specific centrifugal forces over a given period.…”

“…

As centrifugation time can be a bottleneck in coagulation testing, there is a need to determine the impact of rapid centrifugation on the laboratory workflow and TAT. 1,7,9 Several studies have shown that centrifuging samples at higher speeds for shorter durations to obtain PPP has no significant effect on sample integrity and the accuracy of coagulation assay results. 11,12,13,14 Background: The recommendation for coagulation blood samples is to centrifuge at 4000 revolutions per minute (rpm) for 15 min to produce platelet-poor plasma before analysis.

…”

Long COVID-19 and Peripheral Serotonin: A Commentary and Reconsideration

“…In fact, similar spins are recommended and used to prepare plasma largely depleted of platelets for use in coagulation assays. [2][3][4] Given that (1) a marked depletion (4% or less remaining) in platelets is expected for the plasma samples employed, (2) over 99% of blood 5-HT is found in the platelet, 5,6 and (3) typically reported means for whole blood 5-HT are about 1 uM, [7][8][9] one would expect to see mean 5-HT values for plasma so prepared to be about 0.04 uM or less.…”