Sickle discocytes form more rouleaux in vitro than normal erythrocytes.

Rouleaux formation of washed erythrocytes was studied in 32 normal (HbAA) individuals and 30 sickle cell anaemia (HbSS) patients. Washed red cells were suspended in their plasma and rouleaux formation visualized with the aid of an inverted microscope connected to a video camera-monitor unit. Aggregation rate was studied by visual particle counting. Washed sickle discocytes showed rouleaux formation three times as high as normal cells. Red cells were also suspended in buffered Ringer solution containing dextran (a rouleaux inducer). Again, washed erythrocytes from sicklers were about 3 times more aggregable than normal cells at all pH values studied. Increased acidity appeared to aggravate rouleaux formation in both Hb genotypes. We also found plasma fibrinogen concentration in sicklers to be about twice as high as that of normals. High rouleaux formation in sicklers could be attributed not only to fibrinogen and other plasma factors but also to cellular factors.