Plasma viscosity and suspension stability in chronic rheumatic diseases.

In view of the results obtained by the determination of plasma viscosity by Harkness and others (1946) it seemed desirable to apply this method to the chronic rheumatic diseases, but owing to difficulties encountered in procuring the apparatus comparatively few tests had been made before the publication of similar trials by Cowan and Harkness (1947). In the latter paper erythrocyte sedimentation rate figures obtained by the Wintrobe method were compared with the viscosities, and the authors say, " Our results appear to confirm that the viscosity is a more reliable index of clinical condition than the ESR ". They add protocols, in some of which the viscosity was abnormal and the erythrocyte sedimentation rate within normal limits despite an obviously active clinical condition. Previous experience with the Wintrobe technique has shown that it may be grossly inaccurate when the cell volume approximates to the normal level and that normal results may be obtained when the wide-tube method indicates a definite abnormality (Collins and others, 1939). The results reported in this communication were obtained with a micro-viscometer kindly lent by Dr. Harkness and designed by Mr. R. B. Whittington, M.Sc., of Manchester University, to whom I am also indebted for the construction of the ancillary parts of the apparatus and a nomograph for the rapid calculation of the results.