Levels of serum procalcitonin and C-reactive protein for evaluating pulmonary bacterial infection in patients with lupus erythematosus.

The severity of systemic lupus erythematosus (SLE) patients with pulmonary bacterial infection varies widely. We investigated the significance of procalcitonin (PCT) and C-reactive protein (CRP) in evaluating the severity of pulmonary infection in SLE patients. This retrospective study contained a total of 117 patients (107 women and 10 men) with SLE from January 2010 to June 2011. Serum levels of PCT and CRP were measured by enzyme-linked immunosorbent assay. The severity of pulmonary bacterial infection (PBI) was evaluated using the pneumonia severity index (PSI). SLE patients with PBI, particularly those with bacterial isolates, had significantly higher levels of serum PCT and CRP than those without PBI. Serum PCT and CRP were not associated with SLE disease activity, but positively with the values of PSI in active SLE patients with PBI. Serum levels of PCT and CRP may be additional biomarkers in evaluating the severity of PBI in lupus patients.