Prognostic value of simple measurement of chronic damage in renal biopsy specimens

Background. A simple method of measurement of chronic damage in renal biopsy specimens would be useful in clinical management, prognosis, comparisons between different centres and trials. Methods. An interactive image analysis system was used to outline and measure areas of chronic damage in 247 renal biopsy specimens to give an index of chronic damage, expressed as a percentage of cortical cross-sectional area. Prognostic value was analysed by the Kaplan-Meier method to study time between biopsy and onset of permanent dialysis. Results. There was no significant bias between measurements by the same observer or different observers. The index of chronic damage ranged from 0 to 90%. Increasing severity of chronic damage was associated with shortened renal survival. Each increase of 10% in the index increased the hazard ratio of risk of permanent dialysis by 1.5 times (95% confidence interval 1.4-1.7, P<0.001). Conclusions. A simple measure of chronic damage was a powerful indicator of prognosis. This is likely to be clinically useful in routine practice and trials.