Clinical Characteristics and Risk Factors of Diffuse Alveolar Hemorrhage in Systemic Lupus Erythematosus: a Systematic Review and Meta-Analysis Based on Observational Studies.

Diffuse alveolar hemorrhage (DAH) is a rare but potentially deadly manifestation of systemic lupus erythematosus (SLE). The aim of this study was to investigate the clinical characteristics and risk factors of DAH in SLE. A systematic review and meta-analysis of previous observational studies compared the clinical characteristics and risk factors between DAH-SLE and SLE patients without DAH. A total of 5 observational studies were included in this meta-analysis. Compared with the SLE patients without DAH, DAH-SLE patients had a significantly higher incidence of neuropsychiatric events (OR = 4.321, 95% CI (1.686-11.073), P = 0.002, I = 49.2%), nephritis (OR = 3.146, 95% CI (1.663-5.955,), P = 0.000, I = 0.0%), serositis (OR = 6.028, 95% CI (1.418-25.635), P = 0.015, I = 80.3%), dyspnea (OR = 31.241,95% CI (0.202-4833.203), P = 0.181, I = 94.6%), and a significantly lower level of C3 (SMD = - 1.358, 95% CI - 1.685, - 1.031), P = 0.000, I = 98.0%), C4 (SMD = - 1.251, 95% CI (- 1.648, - 0.855), P = 0.000, I = 87.7%), hemoglobin (SMD = - 2.074, 95% CI (- 2.433, - 1.715), P = 0.000, I = 94.2%), and a higher SLEDAI-2K score (SMD = 1.284, 95% CI (0.959, 1.608), P = 0.000, I = 98.2%). However, due to significant heterogeneity, some of these results should be interpreted cautiously. Nevertheless, when the above abnormal indicators are found, especially neuropsychiatric involvement and nephritis, besides the existed diagnostic criteria for DAH in SLE patients, a diagnosis for DAH should be considered and relevant treatment timely initiated. Further prospective multi-center SLE studies with a large cohort of patients and long-term follow-up are needed to clarify further or find out the specific clinical indexes for DAH in SLE patients.