LN Activity Chronicity Indices — SCE Rheumatology MCQ

Correct answer: A — The activity index quantifies active, potentially reversible inflammation; chronicity quantifies established damage, so this active, low-chronicity pattern retains substantial scope for treatment response.

Explanation lettering: C = shown as A · A = shown as C

C is correct. The modified NIH activity index scores active inflammatory lesions, including endocapillary hypercellularity, neutrophils/karyorrhexis, fibrinoid necrosis, hyaline deposits, cellular or fibrocellular crescents, and interstitial inflammation. These lesions may improve with effective immunosuppression. The chronicity index scores glomerulosclerosis, fibrous crescents, tubular atrophy and interstitial fibrosis—established damage associated with poorer renal outcomes and reduced likelihood of response. Thus, activity 8/24 with chronicity 2/12 indicates meaningful active nephritis with relatively little chronic damage and substantial potential benefit from treatment. It does not guarantee response or independently determine the regimen; histological class, kidney function, proteinuria and clinical context remain important. A and E reverse the indices. B incorrectly equates activity with treatment resistance. D is false because the revised indices apply across lupus nephritis classes.

Reference: Bajema IM et al. Revision of the International Society of Nephrology/Renal Pathology Society classification for lupus nephritis: clarification of definitions, and modified National Institutes of Health activity and chronicity indices. Kidney International. 2018;93:789-796. https://pubmed.ncbi.nlm.nih.gov/29459092/