In vitro bromodeoxyuridine labelling of renal biopsy specimens: correlation between labelling indices and tubular damage.

AIMS To examine the correlation between bromodeoxyuridine (BrdU) labelling indices (LI) and tubular damage in renal biopsy specimens; to evaluate the diagnostic and prognostic potential of measuring cell proliferation in a variety of renal lesions. METHODS In vitro BrdU labelling of renal biopsy specimens was undertaken and labelled cells were detected in routinely fixed, paraffin wax embedded sections by immunohistochemistry. The BrdU LI were calculated as percentages for the three types of tubular cells--proximal and distal convoluted tubules and medulla (LI/PCT, LI/DCT, LI/Med)--and a total tubular BrdU LI (LI/Tub) was also calculated for each biopsy specimen. Histological features indicative of tubular damage were also scored and a total tubular damage score obtained for each biopsy specimen. RESULTS The one hour labelling process did not affect tissue morphology or impede subsequent diagnosis. Four biopsy specimens were obtained from three renal transplant recipients. Diagnosis of 19 non-transplant biopsy specimens revealed a variety of renal lesions. Total tubular damage scores ranged from 0 to 25 and the LI/Tub ranged from 0 to 3.68% in all 23 biopsy specimens. Analyses of variance showed highly significant correlations between the total tubular damage score and both LI/Tub (p = 0.004) and LI/PCT (p = 0.004); a weaker correlation was found between the total tubular damage score and LI/DCT (p = 0.013). CONCLUSIONS A correlation was found between tubular damage and BrdU LI. This was most clearly seen in the proximal tubules. However, as the study was limited to a few examples of specific forms of glomerular or interstitial disease, firm conclusions about the value of BrdU labelling in routine diagnosis and prognosis could not be drawn.