Rouleaux formation in sickle cell traits.

Rouleaux formation of washed red blood cells (r.b.c.s) from subjects with sickle cell trait (HbAS) was measured by the rapid coagulation method. The r.b.c.s were suspended in the donor's native plasma or in 1.3% dextran in phosphate-buffered Ringer solution at pHs of 6.5, 7.4 and 8.2. HbAS cells showed more rouleaux formation than HbAA (normal) cells in plasma (P less than 0.005). Plasma fibrinogen concentration of HbAS and HbAA subjects did not differ significantly (mean 2.9, s.d. 0.7 g l-1 for both groups). In the dextran solution, HbAS cells were more aggregable at pH 6.5 but less at pH 8.2 than HbAA cells. There was no significant difference in dextran-induced aggregation between the two groups of cells at pH 7.4. The results suggest that HbAS subjects may be more prone to intravascular sludging and stasis and that this risk may be enhanced by reduction in pH of blood.