In patients with systemic lupus erythematosus (SLE), a positive direct Coombs test in the absence of hemolytic anemia may be correlated with high disease activity and poor renal response, according to the results of a retrospective study published in Lupus.

The investigators sought to determine the clinical utility of the direct Coombs test among patients with SLE without hemolytic anemia as an indicator of disease activity and therapeutic response. A total of 182 patients with SLE were enrolled in the study. Clinical characteristics, including Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), laboratory results, and treatments, were analyzed. In patients with lupus nephritis, cumulative complete renal response rate over the course of 1 year was evaluated as well.

Overall, 5.8% of the participants had a positive direct Coombs test in the absence of hemolytic anemia. These individuals had significantly shorter disease duration (P =.03), higher SLEDAI scores (P <.01), lower platelet counts (P <.01), higher anti-DNA antibody titers (P <.01), lower CH50 (P <.01), higher circulating immune complex levels (P =.03), and lower complete renal response rates (P =.03) compared with those who had negative Coombs tests at baseline. According to multivariate analysis, SLEDAI was shown to be an independent factor linked to the direct Coombs test without hemolytic anemia (odds ratio, 2.4; 95% CI, 1.66-4.98; P <.01).

Major limitations of this study include its single-center design, relatively short observation period, and small sample size. Moreover, all the patients were Japanese, and the study was retrospective in nature.

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The investigators concluded that the presence of a positive Coombs test in the absence of hemolytic anemia may be indicative of excessive immune complex production, and thus may denote a useful biomarker for the evaluation of disease activity and therapeutic response among patients with SLE. Confirmation of these findings in a multicenter, prospective study that enrolls patients of various races is warranted.

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Reference

Hanaoka H, Iida H, Kiyokawa T, Takakuwa Y, Kawahata K. A positive direct Coombs’ test in the absence of hemolytic anemia predicts high disease activity and poor renal response in systemic lupus erythematosus [published online October 25, 2018]. Lupus. doi: 10.1177/0961203318809182