Procalcitonin measurement in routine emergency medicine practice: comparison between two immunoassays.

BACKGROUND

Accurate identification of bacterial infections in patients presenting at the emergency department is crucial for early and rational antibiotic treatment. In this situation, using a cut-off of 0.25 microg/L for procalcitonin allows for carefully monitoring of febrile patients. Most previous studies have been performed with the reference B.R.A.H.M.S PCT KRYPTOR assay. The goal of this study was to compare this test with the VIDAS B.R.A.H.M.S PCT((R)) assay and to validate clinically relevant cut-off thresholds.

METHODS

This prospective study was conducted in adults presenting to the emergency departments of a tertiary hospital. We included 305 consecutive patients that had procalcitonin requested. Procalcitonin was measured first with the KRYPTOR, then with the VIDAS systems. Statistical analysis consisted in Passing and Bablok and Bland-Altman plots.

RESULTS

In the overall cohort, 176 patients had procalcitonin concentrations measured using both methods and were well correlated. The Bland-Altman plot exhibited a bias of 0.108 [95% confidence interval: -0.044 to 0.260]. The concordance at different procalcitonin cut-off thresholds, respectively of 0.1, 0.25, 0.5 and 2 microg/L, indicated that above 0.25 microg/L, the kappa coefficient was >0.80.

CONCLUSIONS

A highly significant correlation was observed between the two automated assays. Procalcitonin concentrations obtained from both methods led to the same clinical interpretation.