Clinical and Analytical Performance Evaluation of an Automated Procalcitonin Assay.

Background: Procalcitonin (PCT) measurement is useful for guiding antibiotic therapy and risk assessment in lower respiratory infections and/or sepsis. This study evaluated clinical and analytical performance of the Vitros® Immunodiagnostic Products B·R·A·H·M·S PCT assay (Vitros PCT).

Methods: Precision, limits of blank (LoB), detection (LoD), and quantitation (LoQ) were determined for Vitros PCT, along with method comparison and clinical concordance with the B·R·A·H·M·S PCT™-sensitive KRYPTOR™ assay (KRYPTOR PCT). All-cause 28-day mortality was evaluated according to the change in PCT values (ΔPCT) from day 0 through day 4 in samples from 598 intensive care unit patients with sepsis.

Results: Comparison of Vitros PCT and KRYPTOR PCT results yielded a Deming regression slope of 1.057, intercept of -0.010, and correlation coefficient (r) of 0.994. Precision analysis demonstrated within-laboratory coefficients of variation for Vitros PCT ranging from 3.1% to 6.4%. The LoD and observed LoQ were determined as 0.007 and 0.013 ng/mL, respectively. Overall agreement between assay methods was 98.5%, 98.0%, 97.4%, and 97.8%, at PCT clinical decision cutoffs of 0.100, 0.250, 0.500, and 2.00 ng/mL, respectively, with Cohen's Kappa coefficients (κ) > 0.91. ΔPCT values ≤80% vs >80% were associated with increased 28-day-all-cause mortality (P = 0.006).

Conclusions: Vitros PCT compares well with KRYPTOR PCT, showing excellent agreement at relevant clinical decision cutoffs that have been used for antibiotic decision-making and assessment of risk for sepsis progression. ΔPCT values determined with Vitros PCT were useful for evaluation of 28-day mortality risk in patients with severe sepsis.