Tamm-Horsfall protein coating of free cells in urine.

The origin of free cells in urine is difficult to determine in the absence of cellular casts. Using fluorescein-conjugated antibody to human Tamm-Horsfall protein (THP), it was demonstrated that some free cells in urine are coated with THP. To evaluate the usefulness of this observation in the differentiation of upper from lower urinary tract disease, the presence of THP coating of cells was correlated with the clinical diagnosis in 141 subjects. The percentage of THP-coated cells for each group (mean +/- SD) was Healthy volunteers (n = 10), 4% +/- 2%; hospitalized controls (n = 20), 3% +/- 3%; glomerulonephritis (n = 21), 61% +/- 6%; chronic interstitial nephritis (n = 26), 56% +/- 5%; other renal parenchymal diseases (n = 14), 50% +/- 8%; bladder disease (n = 14), 8% +/- 2%; and hypertension (n = 36), 24% +/- 33%. Based on the results from the bladder disease group, 12% coating was set as the 95% confidence limit for lower urinary tract disease. The results in this group were not different from control subjects. By analysis of variance and chi 2 analysis, subjects with renal parenchymal disease could be distinguished from those with hypertension and bladder disease (P less than .001 and P less than .0001, respectively). The presence of cellular coating by THP in renal parenchymal disease and its absence in bladder disease suggests that this simple test may be of use in determining the origin of free cells observed in the routine microscopic urinalysis.