Biological variation of procalcitonin levels in hemodialysis patients.

BACKGROUND: There is no obvious evidence regarding biological variation of procalcitonin (PCT) levels in hemodialysis (HD) patients without infections. The aim of this study was to determine the within- and between-person biological variation of PCT levels in HD patients without infections. METHODS: A multicenter, prospective, cohort study enrolled 123 HD patients without any signs of infectious disease. Baseline PCT levels were determined pre- and post-HD, and then repeated pre-HD PCT measurements were performed at 2, 4, 8, 12, 16, 20, and 24 weeks after baseline blood-sampling, regardless of the presence or absence of infectious disease. Analytical variation (CVa), the within-person biological variation (CVi), between-person biological variation (CVb), individual index (II), and the reference change value (RCV) were calculated. RESULTS: The mean age was 62.4 years, 76.4% were male, and 32.5% had diabetes. The mean duration of HD was 87 months. The median value for baseline pre-HD PCT was 0.23 ng/mL, which is much higher than the reference level for healthy individuals. PCT levels decreased of 46.6% after a single HD session. CVi was 24.9%, CVb was 54.2%, II was 0.46, and RCV was calculated as 96.4% with 99% probability. CONCLUSIONS: The PCT level was significantly higher in stable HD patients without manifest bacterial infection. CVb was more variable than CVi in HD patients, which indicates that relative change is more important than absolute PCT levels for diagnosing bacterial infection, and doubling or more of the baseline PCT level may imply the presence of a bacterial infection in HD patients.