Relative Contribution of Morphometric and Functional Indicators of Tubulointerstitial Lesion to Glomerular Diseases Prognosis

Abstract

Background: Early diagnosis of proximal tubular lesions can be achieved by detecting abnormal levels of low molecular weight proteins in urine. Material and Methods: 100 cases of glomerulopathies were retrospectively studied to establish the profile of urinary levels of retinol-binding protein (urRBP) and their correlation with histological markers of tubulointerstitial lesions in renal biopsies. The histological study included staining with picrosirius red. Results: Nonproliferative glomerulopathies, male sex, white race and young adults were predominant. The chance of abnormal urRBP occurring was higher among patients with a predominant proliferative component, baseline serum creatinine >1.2 mg/dl (p = 0.008), creatinine clearance <70 ml/min (p = 0.006), and severe interstitial fibrosis (p = 0.042). In multivariate analysis, only serum creatinine and creatinine clearance were independently associated to urRBP, and only urRBP was a time-independent prognostic factor for survival without renal failure (risk of renal failure: 9×). Conclusion: Our study suggests that urRBP determination is prognostically relevant in the progression of glomerulopathies; on the other hand, the evaluated morphometric markers correlated poorly with the clinical outcome of these patients. Consequently, urRBP determination, as a functional marker of tubulointerstitial damage, was more appropriate for determining the prognosis of glomerular diseases than the morphometric analysis of renal biopsies.