In RA, Lymphocyte Levels May Predict Serious Infection Risk

Among patients with rheumatoid arthritis (RA), lymphopenia might be a precursor to serious infection, in turn making it an appropriate measure to risk stratify patients at high risk, according to new data. “Lymphocyte counts below 1.0 × 109 cells/l were associated with higher [serious infection] risk in RA patients; the strongest association between lymphopenia and [serious infection] was observed when lymphocyte counts were below 0.5 × 109 cells/l,” the researchers wrote. To come to these conclusions, the researchers evaluated data from 1095 adult patients with RA who sought care at a single tertiary rheumatology center. At baseline and over the next 5 years, the researchers collected participants’ lymphocyte counts and tracked their hospital admissions due to serious infections. A Cox proportional hazards regression was used to determine the relationship between the occurrence of serious infection and lymphocyte counts over time. During 2016 person-years of follow-up, 205 serious infections were reported. The serious infection rate was 4.61 per 100 patient-years. “Compared with patients with nadir lymphocyte counts [higher than] 1.5 × 109 cells/l, nadir lymphopenia [ower than] 1 × 109 cells/l was significantly associated with higher risk for [serious infection] (HR 3.28; 95% CI: 1.59, 6.76), increasing to HR 8.08 (95% CI: 3.74, 17.44) in patients with lymphopenia [lower than] 0.5 × 109 cells/l,” the researchers wrote. In the 30-day period prior to serious infection, lymphocyte counts were reduced. —Amanda Balbi   Reference: Subesinghe S, Kleymann A, Rutherford AI, Bechman K, Norton S, Galloway JB. The association between lymphopenia and serious infection risk in rheumatoid arthritis. Rheumatology. 2020;59(4):762-766. https://doi.org/10.1093/rheumatology/kez349