Background/Purpose:

Lupus nephritis is a known predictor of mortality; we have previously shown an increased frequency of nephritis in North American Indian (NAI) and Asian (ASN) lupus patients. We examined the risks of end-stage renal disease (ESRD) and death among lupus nephritis patients, and included the impact of ethnicity, low income (LowInc), lack of education (LowEduc), and living >500 km from rheumatology care (Remote).

Methods:

Patients from a single academic center were followed from 1990-2016 using a custom database. Records of all SLE patients were abstracted. Variables included birthdate, diagnosis date, ethnicity, ACR classification criteria (ACRc), SLICC Damage Index (SDI) including ESRD, treatment and date of death. Ethnicity was categorized into NAI, Caucasian (CAU), ASN and Other. In patients who had developed nephritis, Kaplan Meier and Cox proportional hazard models were used to compare ESRD and survival between vulnerable groups.

Results:

Nine hundred forty-four SLE patients were identified: 240 (25%) NAI, 576(60%) CAU, 104(11%) ASN and 24(2.5%) Other. “Other” patients were excluded. Mean disease duration was 14 years, 89% female. Nephritis developed in 39% of CAU (n= 224), 57% of NAI (n=136; OR 2.1; 95%CI 1.5-2.8), and 75% of ASN (n=76; OR 4.7; 95%CI 2.9-7.6), p<0.001. Twenty percent of patients had not completed high school, 20% were LowInc, and 11% were Remote; LowInc, LowEduc, and Remote did not increase the odds of nephritis. Among nephritis patients, ESRD developed in 11%, and 17% died. Comparing nephritis patients (N=436), NAI (29±15) and ASN (29±13) years were younger at diagnosis; CAU (36±16), p<0.001. Disease duration was similar in NAI and ASN, both (11years±13); and longer in CAU (16±11); p<0.001.There were no differences in additional ACRc met between ethnic groups. SDI in addition to ESRD was similar in NAI (1.8±2.2) and CAU (2.0±2.5) and lower in ASN (1.2±1.4), p=0.04. Odds of ESRD were increased in NAI (OR 2.6; 95%CI 1.3-5.5) and ASN (OR 3.7; 95%CI 1.6-8.2) compared to CAU. LowInc, LowEduc, and Remote did not increase odds of ESRD. Odds of death were increased in NAI (OR 1.9; 95%CI 1.1-3.2), but not in ASN (OR 0.6; 95%CI 0.2-1.4) compared to CAU. LowInc did not increase odds of death, but LowEduc (OR 3.2; 95%CI 1.8-5.5), and Remote (OR 2.9; 95%CI 1.4-6.0) did. In separate models, after adjustment for age, gender, SDI, ACRc, and age at diagnosis, risk of ESRD was increased in NAI (HR 2.8; 95%CI 1.0-8.1) and ASN (HR 4.0; 95%CI 1.6-10.3) compared to CAU. LowInc, LowEduc, and Remote did not increase risk of ESRD. Only LowEduc (HR 2.1; 95%CI 1.1-3.9) increased the adjusted risk of death; ethnicity, LowInc and Remote were not significant.

Conclusion:

Compared to CAU, NAI and ASN not only have a higher risk of nephritis, but among those with nephritis, risk of ESRD is 3-4 fold higher in NAI and ASN. Lack of education, rather than ethnicity, was the major risk factor for death. Reasons for these differences may include renal pathology, care pathways, comorbid conditions and additional socioeconomic factors and need to be further explored.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/outcomes-of-lupus-nephritis-in-vulnerable-populations/