The Effects Of Speed And Duration Of Centrifugation On The Values of Some Commonly Measured Plasma Electrolytes

Centrifugation is a routine process in a clinical chemistry laboratory where blood specimens collected into anticoagulant containers are centrifuged to separate the plasma from the blood cells. This is done at various speeds, times and temperature which most times affect the quality of samples mainly due to haemolysis. World Health Organisation guidelines advocate for a maximum duration of 15 minutes as the centrifugation duration for separation of plasma. Various laboratories in this region adopt various speeds and duration for separation of blood samples without minding any possible effect it may have on the value of certain common analytes. This study was therefore designed to study the effect of different centrifugation speeds and duration (within the scope of the WHO centrifugation time guidelines) on the value of commonly measured analytes like sodium, potassium, chloride and bicarbonate. A cross-sectional study where blood was taken from 30 apparently healthy undergraduate volunteers after dividing the group into A and B of 15 subjects each. From the A group, blood specimens from each subject was separated based on the different centrifugation speeds and from the B group, blood specimens from each subject was separated based on different centrifugation times. The different samples from each subject were analysed for sodium, potassium, chloride and bicarbonate and this was done for all subjects. The mean values of all the analytes were about the same for the 1000 Revolutions per Minutes (RPM), 2000 RPM, 3000 RPM and 4000 RPM and so were the mean values of all the samples labelled 3 minutes, 6 minutes, 9 minutes, 12 minutes and 15 minutes. The differences in the means of the subgroups for group A and group B were statistically not significant. From this study, it can be advocated that plasma can be separated from whole blood samples at a maximum speed of 4000 RPM for 3 minutes duration without affecting the accuracy of most analytes and the introduction of this speed and duration will improve the quality assurance of laboratories in this region.