Background Assessment of procalcitonin (PCT) serum levels is of great interest in current rheumatology practice, due to clinical and laboratory similarity of acute systemic rheumatic diseases (RDs) and acute infectious process, and because of low diagnostic yield of conventional ESR, CRP and WBC in active RDs.

Objectives To evaluate the relevance of PCT as a specific marker of generalised and local infections in patients with RDs.

Methods Medical records of 134 in-hospital patients (mean age 40,6±19,5) admitted to VA Nasonova Research Institute of Rheumatology for examination and treatment were analysed in this retrospective study. Serum PCT concentration was measured using quantitative electrochemiluminescence method, Cobas E 411 analyzer (Roshe, Switzerland). The infectious process was diagnosed in 75 pts, generalised – in 4, and local – in 71. Based on the severity of fever and intoxication local infections were divided into mild – 41 cases, and severe – 30 cases.

Results The PCT level reached >2.0 ng/mL in 3 of 4 cases in generalised infection. In population with severe local infections (n=30) the PCT concentration exceeded the threshold and amounted to 0.60 ng/mL [0.19; 1,84], while in pts with mild infection (n=41) it was 0.13 ng/mL [0,08; 0,25] (table 1). PCT levels positively correlated with ESR, CRP, white blood cell count, and SLE activity according to SLEDAI index in this retrospective study. Maximal PCT levels were found in adult-onset Still’s disease (ASD) pts with high activity of rheumatic process without underlying infection – 0.26 [0.10;0,61] ng/mL. The test’s sensitivity and specificity in generalised/severe local infections group (n=34) were 60% and 82,5%, respectively, with a threshold value of 0.4 ng/mL.

Conclusions PCT quantification is a sensitive and specific method for differential diagnosis of serious bacterial infections in patients with different activity of systemic RD. ASD seems to be the exception, as it was associated with PCT increase in the absence any infection. Further studies are needed to determine PCT thresholds for different RDs.

Disclosure of Interest None declared