Fibrinogen in systemic lupus erythematosus: more than an acute phase reactant?

To investigate whether plasma fibrinogen (FNG) measured longitudinally in a cohort of patients with systemic lupus erythematosus (SLE) increased over observational time faster than in a control group, and whether its increase might depend upon age, disease duration, disease activity, and medications.

Hospital based retrospective study with repeated measurements of plasma FNG and C-reactive protein (CRP) for patients and controls and erythrocyte sedimentation rate (ESR) and lupus activity index (LAI) for patients only. Study groups included patients with SLE: n = 96 (95% female), and healthy controls: n = 39 (95% female). Of the patients, 42% had SLE only, 23% had SLE with antiphospholipid antibodies (aPL), and 34% had SLE with aPL related thrombosis.

Median baseline FNG was higher in patients (357 mg/dl; 95% CI 339-375) than in controls (271 mg/dl; 95% CI 251-291) by 86 mg/dl (95% CI 56-115, p < 0.001); in older subjects than younger (in patients and in controls); in patients with thrombosis than in other patient groups (by an average of 35 mg/dl; 95% CI 9-61 mg/dl): and in patients with longer disease duration (p = 0.05). Mean FNG increased faster in patients (19 mg/dl/year; 95% CI 12-26 mg/dl) than in controls (2.6 mg/dl/year; 95% CI 2.0-3.2 mg/dl). The increase was faster than the age effect and independent of patient group and disease activity.

Plasma FNG in patients with SLE increases throughout followup regardless of disease activity, mimicking the age related increment observed in population based studies. The rapidity of the increment may reflect the prematurity of vascular disease typical of SLE.