Serum procalcitonin levels in patients with ankylosing spondylitis

Procalcitonin is a marker of bacterial and fungal infection and sepsis. The present study evaluated the relationship between serum procalcitonin levels and disease activity in patients with ankylosing spondylitis (AS).

A total of 61 patients who met the 1984 New York criteria for AS were studied. Twenty-four age- and sex-matched healthy volunteers were recruited to this study as a control group. Disease activity was assessed by the Bath AS Disease Activity Index (BASDAI). The functional status of patients was evaluated by the Bath AS Functional Index (BASFI). Spinal mobility was measured by the Bath AS Metrology Index (BASMI). Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and serum procalcitonin levels were measured.

Thirty patients were on anti-tumor necrosis factor-alpha treatment and 31 patients were on conventional treatment. Seventeen (28%) of the AS patients were active (BASDAI > 4) and 44 (72%) of the AS patients were in remission. The median ESR was 14 (34-6) mm/h and 4 (7-2) mm/h (P < 0.001) for the patient and control groups, respectively. The median CRP level was 0.91 (2.72-0.37) mg/dL and 0.15 (0.25-0.07) mg/dL in the patient and control groups, respectively (P < 0.001). Median BASDAI, BASFI and BASMI scores for all AS patients were 3.6 (5.25-2.29), 2.5 (4.22-0.91) and 3 (5-1), respectively. Serum procalcitonin levels were normal (< 0.05 ng/mL) for all patients and controls.

Serum procalcitonin levels were not high in AS patients and controls, and the levels were independent of disease activity and medications. If bacterial or fungal infection is suspected in an AS patient, serum procalcitonin level may be useful for diagnosis.