BackgroundRed blood cell aggregation is largely influenced by hematocrit and plasma protein content with aggregation increasing as hematocrit and fibrinogen increase. Aggregation measurement techniques include light-transmission or laser-backscatter, and the impact of measurement technique on aggregation measurements with respect to changes in hematocrit and plasma protein is not well understood.ObjectiveThe objective of this study was to evaluate aggregation measurement techniques with respect to common effectors of red blood cell aggregation.MethodsWe obtained whole blood samples from 10 healthy participants and varied hematocrit, plasma albumin, and plasma fibrinogen concentration in a sample of healthy male and female participants. We then measured red blood cell aggregation using a Myrenne Aggregometer (light-transmission aggregometer) and a Laser Optical Rotational Red Cell Analyzer (laser-backscatter aggregometer).ResultsFor Myrenne, aggregation increased from 30% to 40% hematocrit, then declined at 50% hematocrit. Measurement in the LORRCA demonstrated an increase as hematocrit increased from 30% to 40%, and again increased at 50%, which differed from the light transmission method. Red blood cell aggregation increased with increased fibrinogen concentration, but did not change significantly as albumin concentration increased.ConclusionsRed blood cell aggregation is expected to increase as hematocrit increases, but when light transmission aggregometry is used, aggregation decreases as hematocrit increases past 40%. Each measurement technique has its own set of methodological strengths and weaknesses.