The erythrocyte sedimentation rate and the plasma viscosity.

Certain factors are common to the erythrocyte sedimentation rate and the plasma viscosity. Thus fibrinogen increases the erythrocyte sedimentation rate (Gram, 1921 ; Greisheimer, Johnson, and Ryan, 1929) and Hardwicke, Ricketts, and Squire (1950) found that a direct logarithmic relation exists between the erythrocyte sedimentation rate and the plasma fibrinogen concentration. Also fibrinogen exerts the greatest effect of the plasma protein fractions, weight for weight, on the plasma viscosity (Naegeli, 1931). Globulin increases the sedimentation rate but not to the same extent as does fibrinogen, weight for weight (Ley, 1922; Linzenmeier, 1923; Fahraeus, 1929); similarly, globulin exerts a greater effect than albumin and a lesser effect than fibrinogen, weight for weight, on the plasma viscosity. That the plasma viscosity is affected mainly by the plasma proteins and only slightly influenced by the non-protein constituents is known (Naegeli, 1931 ; Cowan and Harkness, 1947), and Miller and Whittington (1942) state that the plasma viscosity can be taken as an index of the power of the plasma to cause red cell aggregation and rouleaux formation. Whittington (1942) was able to correlate the maximum erythrocyte sedimentation rate with the plasma viscosity and the whole blood viscosity. (This latter value is affected by the degree of the red cell aggregation.) Thus the plasma proteins have a significant effect on both the erythrocyte sedimentation rate and the plasma viscosity. Many hydrophilic colloids besides plasma are capable of causing red cell aggregation with increased rates of sedimentation; these include gum acacia, gelatin, agar agar, and casein solutions (F&hraeus, 1929), and Hardwicke and Squire (1952) showed that the concentrations of macromolecules, such as fibrinogen, dextrans, gelatin, gum acacia, and polyvinyl pyrrolidone bore a linear relation to the maximum erythrocyte sedimentation rate. Also, they showed that the degree of the effect on the maximum erythrocyte sedimentation rate varied with the size of the macromolecules. Comparing the maximum erythrocyte sedimentation rate of various blood samples, at a constant haematocrit value of 45%, with their corresponding plasma viscosity values, it was found that out of 99 results, 96 showed a direct correlation between the maximum erythrocyte sedimentation rates and the plasma viscosity values, but three blood samples with very high plasma viscosity values had much slower maximum erythrocyte sedimentation rates than was expected. The possible reasons for this disparity were examined.