Abstract and Introduction
Abstract
Background: Leukopenia is a common finding in systemic lupus erythematosus (SLE) and may contribute to severe infections.
Objectives: The objectives of this study were to determine the prevalence of leukopenia in SLE patients and examine the association between these conditions and severe infections noting the risk factor of severe infections.
Methods: This study was a prospective inception lupus cohort of newly diagnosed SLE patients seen between May 2007 and June 2011. Only cases that had been observed for a minimum of 1 year or died during the study were included.
Results: There were 89 SLE patients (92% females), with their mean (SD) age and disease duration at the study entry of 31.7 (12.2) years and 2.4 (2.9) months. Leukopenia was found at the diagnosis in 51.6% of the cases. The cumulative prevalence of leukopenia, lymphopenia, and neutropenia was observed in 57.3%, 96.6%, and 60.7%, respectively. Persistent lymphopenia, noted continuously for more than or equal to 75% of the observation period, was found in 41.6%, but there was no persistent neutropenia. The incidence rate of severe infection was 12.4 per 100 patient-years. There was no difference of severe infection–free survival rate between patients who ever and never had leukopenia. In the multivariate analysis, using cyclophosphamide was the independent predictor for severe infection in SLE (hazard ratio, 2.73; 95% confidence interval, 1.10–6.77).
Conclusions: Leukopenia was common in SLE but usually not persistent. In this study, the presence of leukopenia at any time was not the risk factor for severe infection in SLE. Cyclophosphamide was the important predictor for severe infection in SLE.
Introduction
Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease with multiple organ involvement. Hematologic abnormalities, including anemia, thrombocytopenia, leukopenia, and lymphopenia, are commonly found in SLE patients. Leukopenia is common in SLE and is included in both the American College of Rheumatology (ACR) and the Systemic Lupus International Collaborating Clinics (SLICC) classification criteria of SLE. Leukopenia in SLE may result from SLE disease activity or bone marrow suppression from immunosuppressant(s), comedications, or other medical conditions. As white blood cells (WBCs) have a major role in the immune system in preventing infection, leukopenia may contribute to severe infections in SLE.
Infection is the most common cause of morbidity and mortality in SLE. Many previous studies demonstrated that infection is the common risk factor for hospitalizations and death. The risk factors for infection that had been reported were disease activity, immunosuppressive agents, corticosteroids, and leukopenia.
The association between leukopenia and severe infection remains controversial in SLE. Some studies showed lymphopenia at presentation and neutropenia associated with infection in SLE, but other studies do not support the role of leukopenia as a predisposition to severe infection in SLE.
The association between leukopenia and infection is a time-dependent relationship. Thus, the number of WBCs at diagnosis or at only 1 time point may not predict an infection in subsequent times. Therefore, the purpose of this study was to examine the association between 3 WBC conditions (leukopenia, lymphopenia, and neutropenia) over a period of time and severe infection in SLE patients from an inception cohort study.