Evaluation of activity, chronicity and tubulointerstitial indices for childhood lupus nephritis

Few data exist on use of the National Institutes of Health (NIH) activity index (AI) and chronicity index (CI) in childhood lupus nephritis (LN). A tubulointerstitial activity index (TIAI) has been derived but not validated. We evaluated clinicopathologic correlations of the AI, CI and TIAI in children with LN who had undergone initial renal biopsy (n=25, age 12.4+/-2.7 years, biopsy 1) and 1 year after treatment (n=15, biopsy 2). The TIAI correlated with the AI at biopsy 1 (r=0.76, P=0.001) and biopsy 2 (r=0.52, P=0.05), but not with CI scores. Mean AI and CI scores changed substantially from biopsy 1 to biopsy 2 (P<0.05), but TIAI scores did not. Higher AI and TIAI scores correlated with proteinuria at both biopsies (r=0.51-0.76, P<0.05); CI scores correlated with estimated creatinine clearance (r=0.46-0.58, P<0.05). Improved AI score from biopsy 1 to biopsy 2 was associated with decrease in proteinuria. These results suggest that the AI and CI are useful in childhood LN. The TIAI may be a valid measure to evaluate the tubulointerstitium, but research is needed to define its responsiveness to change with therapy.