Objective This study aimed to compare choroidal thickness between patients with systemic lupus erythematosus (SLE) and lupus nephritis (LN) in complete renal remission to that of patients with SLE without LN. Methods This was a retrospective case-control study of 23 SLE patients meeting either the American College of Rheumatology or Systemic Lupus International Collaborating Clinics classification criteria and followed at Washington University School of Medicine Rheumatology or Nephrology, and Ophthalmology outpatient clinics. The diagnosis of LN was based on renal pathology, and complete renal remission was defined as proteinuria <500 mg/daily and serum creatinine at baseline. Extra-renal flare status was determined using modified Fortin criteria. Choroidal thickness was measured using spectral-domain optical coherence tomography and read by blinded reviewers. Results In SLE patients without extra-renal flare, choroidal thickness of LN patients was 281 ± 78 µm compared to 288 ± 70 µm in non-LN SLE patients ( p = 0.766) at the fovea. Conclusion Choroidal thickness was not different in patients with LN in remission compared to non-LN SLE patients in remission. Additional studies are needed to examine choroidal thickness in patients with SLE with active LN.

Objective International Classification of Diseases (ICD) codes are commonly used to identify patients with rare diseases in electronic health records (EHRs). However, misclassification is common, impacting the validity of study results. In this study, we compared the accuracies of several ICD-based case definitions of lupus nephritis (LN) in identifying United States veterans with LN. Methods Using the Department of Veterans Affairs (VA) EHR, we identified all veterans with ≥1 ICD-9 or 10 diagnostic codes for systemic lupus erythematosus (SLE) between October 1, 1999 and September 30, 2017. A cohort was randomly selected for diagnostic validation and 9 ICD-based LN case definitions were applied to this cohort. The diagnostic accuracy of each definition was assessed against gold standard criterion of biopsy-proven LN. Results 18,420 veterans had ≥1 ICD-9 or 10 diagnostic codes for SLE; 981 were randomly selected for diagnostic validation. 95 veterans (9.7%) had biopsy-proven LN. The case definitions had high specificity and NPV but variable sensitivity and PPV. The definition containing ≥2 ICD -9 codes for SLE and ≥2 nephritis indicators had the highest combination of sensitivity and specificity (87.4% and 94.6% respectively). ICD-10 code for LN had high specificity (99.8%) and PPV (93.9%). Conclusion ICD-based case definitions of LN in the VA population have high specificity and NPV but variable sensitivity and PPV. Our results may help guide the design of future LN studies in VA cohorts. The choice of specific case definitions depends on the relative importance of different accuracy measures to individual studies.