A new morphologic index for the evaluation of renal biopsies in lupus nephritis

Background. Various morphologic indices for the evaluation of renal biopsie s in lupus nephritis have been developed, of which the most successful have been the NIH Activity Index (AI) and Chronicity Index (CI). We wished to d evelop a biopsy index from standard light and immunofluorescence (IF) mater ial that would correlate yet more closely with clinical and outcome paramet ers than the current indices, and be applicable to both treated and untreat ed cases. Methods. A cohort of 71 patients with lupus nephritis who had initial renal biopsies (Bx1) with systematic second biopsies (Bx2) at six months after i nduction therapy was studied, with a large number of light microscopic and IF variables evaluated. These were examined statistically to choose the com binations of variables with the highest overall correlations with clinical and outcome parameters. Results. The adopted biopsy index comprised four elements: Glomerular Activ ity Index (GAI), a modification of the standard AI with the addition of glo merular monocytes and elimination of interstitial inflammation; Tubulointer stitial Activity Index (TIAI), evaluating several tubular epithelial and in flammatory components, including interstitial inflammation, but excluding t ubular atrophy; Chronic Lesions Index, a modification of the standard CI, w ith the addition of glomerular scars: IF Index (IFI), a semiquantitative in dex of IF staining for six standard antisera for glomerular capillary, mesa ngial, tubulointerstitial, and vascular elements. The Biopsy Index showed a statistically higher correlation with clinical and outcome parameters than the NIH AI (P = 0.0170), the NIH CI (P = 0.0009), or their combination (P = 0.0444). At Bx1, comparisons between correlation coefficients for the app ropriate AI or CI value and for the Biopsy Index, were: anti-DNA antibodies (0.30 vs. 045), serum creatinine (S-Cr; 0.33 vs. 0.48). proteinuria (0.22 vs. 0.36), hemoglobin (-0.21 vs. -0.45), and final renal function (0.22 vs. 0.40). Spearman rank correlations showed similar superiority for outcome p arameters: doubling of S-Cr (0.1810 vs. 0.3018) and end-stage renal disease (0.0529 vs. 0.1925). The same improvement of correlations was seen at Bx2 for most parameters, particularly doubling of S-Cr (0.2716 vs. 0.4753). Conclusions. The Biopsy Index and/or its components show better correlation s with clinical and outcome parameters than the standard AI and CI and othe r similar indices.