Explanatory histological findings for urinary protein and serum creatinine levels at renal biopsy in lupus nephritis: A cross-sectional study

Background To evaluate histological active and chronic lesions associated with proteinuria and serum creatinine (SCr) level as common clinical endpoints in many clinical trials for lupus nephritis (LN).Methods One hundred and nineteen patients from 1990 to 2015 with LN class III, IV, and V, as defined by the International Society of Nephrology/Renal Pathology Society classification, were enrolled. Multiple regression analysis was performed to explore semiquantitative histological variables related to urinary protein and SCr levels.Results The mean age of enrolled patients was 45 years and 79% were female. The mean SCr level was 0.87 mg/dl and mean urinary protein was 3.00 g/gCr at the time of the renal biopsy. Class IV (71%) was the most common type, followed by class III (17%) and class V (13%). Multicollinearity was confirmed between monocellular infiltration (variance inflation factor [VIF] = 10.22) and interstitial fibrosis (VIF = 10.29) and between karyorrhexis (VIF = 4.14) and fibrinoid necrosis (VIF = 4.29). After excluding fibrinoid necrosis and monocellular infiltration because of multicollinearity, only urinary protein level was correlated with wire loop (β−coefficient [β]: 1.09 and confidence interval [CI]: 0.35 to 1.83), and SCr level was correlated with glomerular sclerosis (β: 1.08 and CI: 0.43 to 1.74) by multiple regression analysis.Conclusion As urinary protein and SCr levels could not reflect active lesions quantitatively, they might be difficult to be evaluated for response to induction remission treatments in patients with LN.