A positive direct Coombs' test in the absence of hemolytic anemia predicts high disease activity and poor renal response in systemic lupus erythematosus

We determined the clinical utility of the direct Coombs' test in the absence of hemolytic anemia as an indicator of disease activity and therapeutic response in systemic lupus erythematosus (SLE). SLE patients without hemolytic anemia who visited our hospital from January 2016 to November 2016 were retrospectively evaluated with a direct Coombs' test. Clinical features, including SLE disease activity index (SLEDAI), treatment and laboratory findings were analyzed. For patients with lupus nephritis, we additionally evaluated the cumulative complete renal response rate over one year after induction therapy. Among 182 patients evaluated, 10 (5.8%) patients had a positive direct Coombs' test in the absence of hemolytic anemia. They had a higher SLEDAI (p < 0.01), higher circulating immune complex levels (p = 0.01), higher anti-DNA titers (p < 0.01) and a lower complete renal response rate (p = 0.03) compared with those who were negative. Multivariate analysis indicated that SLEDAI was an independent factor correlated with the direct Coombs' test without hemolytic anemia (odds ratio 2.4, 95% confidence interval 1.66-4.98, p < 0.01). A positive direct Coombs' test in the absence of hemolytic anemia may therefore represent a useful biomarker for assessing disease activity and therapeutic response.