Serum uric acid as a sensitive concordant marker with lupus nephritis and new onset of renal damage: a prospective cohort study.

OBJECTIVE

The objectives of this study are to assess serum different uric acid levels among systemic lupus erythematosus patients with or without active lupus nephritis in comparison to healthy controls and to study the relation of baseline uric acid levels to the development of new-onset renal damage in lupus nephritis.

METHODS

This is a case-control study followed by a prospective cohort of systemic lupus erythematosus (SLE) patients. Three groups were included; all were having normal kidney function, 25 SLE patients with recently diagnosed active lupus nephritis (LN), 26 SLE patients without LN, and 38 healthy controls. Serum uric acid (SUA)and serum creatinine were done for all groups; for SLE patients, 24-h protein in the urine, urinalysis, C3, C4 levels, anti-DNA, anti-ENA antibodies, SLE Disease Activity Index (SLEDAI), and SLICC/ACR damage index (SDI) evaluation were also calculated. Follow-up was done with clinical and laboratory assessment including SUA, with SLEDAI and SDI evaluation.

RESULTS

Serum uric acid was significantly higher in SLE patients with active LN than the other two groups (p < 0.05), a cutoff value of serum uric acid associated with lupus nephritis onset was 0.41 mmol/L with a sensitivity of 58% and specificity of 100%, however, C3 and C4 showed very low sensitivity and specificity. During follow-up, all patients with LN with baseline serum uric acid ≥ 0.52 mmol/L were associated with new-onset renal damage within 43 months.

CONCLUSIONS

High-serum uric acid levels showed a significant association with lupus nephritis onset and new onset of renal damage. Key Points • Serum uric acid is a cheap, rapid, and popular test available in most of the worldwide laboratories; its higher levels showed a significant association with lupus nephritis onset and new onset of renal damage • The current work is the largest study done on lupus nephritis with strict control to the confound risk factors that are associated with the increase of the uric acid levels; moreover, it is the first study to assess such relation in Saudi population • Uric acid could have a role in the pathogenesis of lupus nephritis patients and consequent renal damage.