Prognosis of patients with systemic lupus erythematosus is improved due to immunosuppressive treatment. However, the treatment and immunological abnormalities as a consequence of the disease, can contribute to increased risk for serious infections. Discrimination between flare of the disease and infectious complication is difficult. Procalcitonin is a biomarker that is currently used to differentiate systemic inflammatory response of bacterial and non-bacterial etiology in critically ill patients. Sensitivity and specificity of increased procalcitonin levels differ in various studies. This article summarizes the basic data on the role of procalcitonin, particularly its usefulness in rheumatology. Because the level of procalcitonin is rapidly increased by serious bacterial or mycotic infection, but not by autoimmune process or glucocorticoid treatment, we suggest procalcitonin as a valuable surrogate marker to differentiate between those conditions. Furthermore, we assume that combination of procalcitonin (higher specificity) and C-reactive protein (higher sensitivity) assessments together with serum complements C3 and C4 may contribute to discrimination between those two situations that need completely different therapeutical approach.

        Key words: procalcitonin, autoimmune, infection