A 45-year-old woman with lupus nephritis (class IV by ISN/RPS classification) is being treated with mycophenolate mofetil (MMF) and prednisolone. After 6 months, repeat biopsy shows persistent class IV activity with chronicity index of 5/12. What is the significance of the chronicity index in decision-making?

• A High chronicity index mandates switching to cyclophosphamide
• B Chronicity index guides the duration of remission induction phase
• C High chronicity index (>4) predicts poor renal outcome regardless of immunosuppression intensity ✓
• D High chronicity index is a contraindication to renal transplant in lupus

Explanation

In lupus nephritis, the National Institutes of Health (NIH) Chronicity Index scores irreversible lesions (glomerulosclerosis, fibrous crescents, tubular atrophy, interstitial fibrosis). A chronicity index >4 is associated with poor long-term renal prognosis regardless of immunosuppressive therapy, because these are irreversible changes. A high activity index (>12) suggests benefit from aggressive immunosuppression. Transplant decisions are not formally contraindicated by chronicity index alone; transplant is actually performed in end-stage lupus nephritis.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.