The role of plasma fibrinogen, D-dimer and fibrinogen degradation products in diagnosis and disease activity in patients with ankylosing spondylitis

To evaluate the role of coagulation-related markers such as plasma fibrinogen, D-dimer and fibrinogen degradation product (FDP) in ankylosing spondylitis (AS) patients and their relationship with disease activity. Data were collected from 210 AS patients and 204 age and gender matched healthy controls. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was used to divide AS patients into active (≥4) and inactive (score < 4) groups. The mean age of the patients was 35.3 ± 16.3 years. They were 156 males and 54 females (M:F 2.9:1) and had a disease duration of 9.4 ± 7.2 years. The mean fibrinogen, D-dimer and FDP were significantly increased in the patients (375.4 ± 125.01 mg/dl, 2874.8 ± 1884.6 ug/l and 18.3 ± 11.3 mg/l) compared to the control (276.7 ± 71.9 mg/dl, 913.3 ± 540.6 ug/l and 3.01 ± 1.2 mg/l respectively; p < 0.001 each). Plasma fibrinogen, D-dimer and FDP increased in active compared to inactive patients (p < 0.001) and were significantly associated with BASDAI (p < 0.001). The optimal cut-off value of plasma fibrinogen, D-dimer and FDP for the diagnosis of AS were >288 mg/dl, >472 ug/l and >1.44 mg/l while to discriminate active from inactive the values were 393 mg/dl, 1228 μg/L and 1.82 mg/L, respectively. Logistic regression analysis showed that D-dimer is an independent predictor for AS disease activity (OR = 2.85, 95%CI: (1.85--4.43), p < 0.001). Fibrinogen, D-dimer and FDP increased in AS patients and significantly correlated with disease activity. D-dimer may play a role as a novel inflammatory parameter to predict disease activity in AS patients.