Procalcitonin levels at hospital admission are increased in cyst infection in patients with autosomal dominant polycystic kidney disease.

Introduction: The diagnosis of cyst infection in autosomal dominant polycystic kidney disease (ADPKD) is difficult. [18F]FDG PET/CT imaging is helpful, but early diagnosis remains challenging. Procalcitonin (PCT), a serum biomarker for bacterial infections, has not been evaluated in ADPKD-related cyst infections.

Methods: A retrospective review (between 2009 and 2023) identified all ADPKD patients who were (i) hospitalized (ii) with serum PCT measurements. Cyst infection was conventionally defined. Univariate and multivariate logistic regressions assessed the association between PCT and cyst infection risk.

Results: The cohort included 104 patients (mean age of 65.5 ± 14.9 years; 49% post-kidney transplantation; 16.3% on chronic dialysis). Cyst infections occurred in 24 cases. [18F]FDG PET/CT was performed in 47 patients, detecting cyst infection in 17 cases and non-cystic inflammation in 11. In the whole cohort, CRP levels at admission reached 97.3 [42.8; 164] mg/L. Serum PCT level was measured within 72-h post admission in 83/104 (79%) cases, and the median value reached 0.47 [0.18-2.04] µg/L. A significant correlation was observed between serums levels of PCT and creatinine at admission (r = 0.37, p < 0.05). PCT > 0.59 µg/L significantly predicted cyst infection (OR = 6.30, p = 0.0047). Antibiotics were administered ≥48 h before PCT measurement in 9/24 cases of cyst infection. PCT levels did not significantly differ between patients exposed to antibiotics (0.98 [0.43-2.19] µg/L) or not (1.42 [0.94-3.81] µg/L; p = 0.39). Higher PCT was associated with cyst [18F]FDG uptake above the pathological threshold (OR = 2.01, p = 0.0028).

Conclusion: PCT >0.59 µg/L within 72-h post admission is a significant biomarker for cyst infection in ADPKD patients.