Background: Clinical manifestations of infection in patients with systemic lupus erythematosus (SLE) are variable and involve significant diagnostic challenges. Delays in diagnosis and treatment strongly affect the clinical outcomes and mortality. The elevation of one’s serum procalcitonin (PCT) level may be a diagnostic biomarker of infection in SLE.

Objective: To determine the diagnostic accuracy of PCT for bacterial and fungal infections in patients with SLE.

Materials and Methods: Samples of serum PCT were prospectively collected in all patients with SLE admitted to medical wards at Siriraj Hospital, a tertiary care center, between February 2011 and March 2012.

Results: One hundred twenty-four patients with SLE were enrolled. The mean age was 31.9±10.9 years. The median disease duration of SLE was five years. The Median Mexican SLE Disease-Activity Index Score was 8 (IQR 6 to 11.8). Ninety-five percent of patients had active SLE and 70% of them were treated with prednisolone of more than 15 mg/day or equivalent doses of other corticosteroids. The serum PCT levels of SLE patients with infection (n=39; median 0.52 ng/mL, IQR 0.15 to 1.49) were significantly increased, compared to those of SLE patients with no infection (n=85; median 0.09 ng/mL, IQR 0.04 to 0.16), p<0.001. The cut-off point of elevated serum PCT (0.5 ng/mL) for the diagnosis of bacterial or fungal infections in patients with SLE had sensitivity, specificity, positive predictive value, and negative predictive values of 51.3%, 95.3%, 83.3%, and 81%, respectively. The independent factors associated with elevated serum PCT levels of 0.5 ng/mL or more were the presence of a bacterial or fungal infection, a low hemoglobin level, and serum Cr of 2 mg/dL or more.

Conclusion: The elevation of one’s serum PCT level may be a useful biomarker to detect bacterial and fungal infections in patients with SLE.

Keywords: Systemic lupus erythematosus; Procalcitonin; Sensitivity; Specificity; Infection; Sepsis; Flare

DOI: doi.org/10.35755/jmedassocthai.2021.06.12098

Received 28 December 2020 | Revised 26 January 2021 | Accepted 26 January 2021