Microscopic examination of urine.

Two methods of expressing microscopically observed leucocytes, erythrocytes, and casts in urine, both with centrifugation, one quantitatively (per ml) and the other per high-power field (H.P.F.), were compared for reliability in predicting renal functional abnormalities. In a series of 88 duplicate urines, abnormal numbers of casts or white or red blood-cells were detected by the quantitative method im 74% of patients with abnormal renal function but in only 36% by the N.P.F. method. The hourly excretion-rate of leucocytes over 3 1/2 h correlated very closely with the leucocyte concentration (cells/ml) measured by the quantitative method, so that a timed collection of urine was unnecessary. Unless findings from urinary microscopy can be relied upon, through adoption of a quantitative method, abnormal urines may be judged normal and some cases of glomerulonephritis may be falsely designated "clinically silent".