Can we predict kidney involvement in patients with systemic lupus erythematosus? A retrospective cohort study with independent validation

Abstract

Objectives: To discern predictive factors for incident kidney involvement in patients with SLE. Methods: Patients with SLE from the ‘Attikon’ Lupus cohort were monitored for LN, defined by kidney histology and/or classification criteria. Demographic and clinical characteristics at baseline were compared against patients who did not develop LN. LN-free Kaplan–Meier survival curves were generated. A multivariate Cox proportional hazards model was used to identify independent predictors of LN. Independent validation was performed in the University of Crete Lupus registry. Results: Among the 570 patients in the derivation cohort, 59 exhibited LN as their initial presentation, while an additional 66 developed LN during the follow-up period (collectively, 21.9% incidence). In the latter group, baseline factors predictive of subsequent kidney involvement were male sex [multivariable-adjusted hazard ratio (aHR) 4.31; 95% CI: 1.82, 10.2], age of SLE diagnosis below 26years (aHR 3.71; 95% CI: 1.84, 7.48), high anti-dsDNA titre (aHR 2.48; 95% CI: 1.03, 5.97) and low C3 and/or C4 (although not statistically significant, aHR 2.24; 95% CI: 0.83, 6.05; P=0.11). A combination of these factors at time of diagnosis conferred an almost 90-fold risk compared with serologically inactive, older, female patients (aHR 88.77; 95% CI: 18.75, 420.41), signifying a very high-risk group. Independent validation in the Crete Lupus registry showed concordant results with the original cohort. Conclusion: Male sex, younger age and serological activity at SLE diagnosis are strongly associated with subsequent kidney involvement. Vigilant surveillance and consideration of early use of disease-modifying drugs is warranted in these subsets of patients.