In patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), the biomarker procalcitonin (PCT) may have the ability to distinguish between infections and disease flare, according to findings from a retrospective, case-control study published in the International Journal of Molecular Sciences.

AAVs are recognized as “necrotizing systemic vasculitides of unknown cause affecting small vessels.” Among individuals with proinflammatory disorders such as AAV, certain cells and organs are known to accelerate PCT production.

The researchers sought to establish whether PCT exhibits effectiveness in differentiating between bacterial infections and AAV-linked disease flare. Potential differential factors, including temperature above 38 °C, levels of certain leukocytes, and concentration of fibrinogen, were evaluated as well.

One hundred thirty-seven individuals with AAV were investigated, with 63 patients without PCT assays ultimately excluded from the study. Thus, 74 participants were included in the analysis. The median patient age was 64 years (range, 51-73 years). Overall, 44 participants were men and 30 were women.

Learn more about ANCA-AAV diagnosis

Diagnoses in the 74 patients included 43 cases of granulomatosis with polyangiitis (GPA), 21 cases of eosinophilic GPA, and 10 cases of microscopic polyangiitis. The characteristics of 88 episodes of infection confirmed by a PCT assay (ie, the “infected group’) were compared with those of 72 relapses confirmed by a PCT assay (ie, the “relapsing group”).

Results of the study revealed that median PCT levels were statistically significantly higher in the infected arm compared with the relapsing arm (0.2 μg/L [95% CI, 0.08-0.935 μg/L] vs 0.09 μg/L [95% CI, 0.05-0.2 μg/L], respectively; P <.001).    

The median C-reactive protein levels were 64.7 mg/L [95% CI, 25-131 mg/L] in the infected cohort vs 31.5 mg/L [95% CI, 10.6-120 mg/L] in the relapsing cohort (P =.001).

Regarding infection, the sensitivity and specificity of PCT were 53.4% and 73.6%, respectively; the optimal threshold was 0.2. In terms of C-reactive protein concentrations, the sensitivity and specificity were 94.2% vs 11.3%, respectively; the ideal threshold was 5 mg/L. No significant differences were reported between the groups with respect to white blood cell counts, neutrophil counts, eosinophil counts, and fibrogen levels.

Read more about ANCA-AAV treatment

Per multivariate analysis, a PCT value of 0.2 µg/L or more was associated with a statistically significant relative risk for infection of 2.14 (95% CI, 1.02-4.50; P =.04).

“Our study suggests that PCT may be useful for discriminating between infections and flare in patients [with] AAVs,” the authors noted. “However, new diagnostic markers are being investigated. The improvement of technologies for biological assays allows, currently, a wide screening of proteins secreted in response to bacterial or viral infection. Other biological markers (presepsin and endocan) could be relevant for differentiating infection from AAV relapse, but they are not currently routinely measured,” they concluded. 


Poirot-Seynaeve X, Smets P, Pereira B, et al. Interest of procalcitonin in ANCA vasculitides for differentiation between flare and infections. Int J Mol Sci. 2023;24(6):5557. doi:10.3390/ijms24065557