The impact of measurement techniques and common effectors on red blood cell aggregation.

Background: Red 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.

Objective: The objective of this study was to evaluate aggregation measurement techniques with respect to common effectors of red blood cell aggregation.

Methods: We 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).

Results: For 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.

Conclusions: Red 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.