Comparison of a New Procalcitonin Assay from Roche with the Established Method on the Brahms Kryptor

Abstract

Procalcitonin (PCT) is a 13-kDa peptide and a precursor of calcitonin. In a healthy population, PCT concentrations are negligible (1 ). In systemic bacterial and fungal infections, plasma concentrations are raised, whereas concentrations remain fairly low in infections of viral or nonspecific cause (2 ). Recent studies have demonstrated the potential of PCT as a parameter to guide antibiotic therapy in different groups of patients, i.e., patients with chronic obstructive pulmonary disease experiencing respiratory tract infections (3,4 ). The most frequently used medical decision points at which the use of antibiotic therapy is considered are 0.25 g/L and 0.50 g/L, depending on the patient population (3, 4 ).The first PCT assays were based on manual immunochemistry methods (Brahms PCT LIA). These assays have been replaced by fully automated immunochemistry methods (Brahms Kryptor, Brahms LIAISON, Olympus SphereLight 180). Recently, the PCT assay has been modified for use on a consolidated routine immunochemistry analyzer family, the Roche Elecsys, cobas, and the Roche Modular E170 systems. We evaluated the analytical performance of this new assay by following the EP10 protocol, a document from the Clinical and Laboratory Standards Institute to test precision, linearity, recovery, carryover, and drift. Samples were prepared at different concentrations, from 0.24 -2.85 g/L. Three aliquots of each concentration were assayed on 5 different days, in a specific assay order. The within-run CV ranged from 3.0% for the lowest concentration to 1.3% for the highest concentration. The between-day CV ranged from 6.3% for the lowest concentration to 2.8% for the highest. These levels of imprecision were comparable with those reported for the PCT assay on the Brahms Kryptor (5 ). The mean recovery was 99%. There was no evidence of nonlinearity or sample carryover. The limit of quantification, i.e., the lowest concentration of analyte that can be quantified with a between-run imprecision of Ͻ20%, met the manufacturer's specification of 0.06 g/L. In addition, we compared the new PCT assay from Roche on the Modular 170 with the widely accepted PCT assay from Brahms on the Kryptor (5 ). For analytical comparison, we used 229 samples of patient serum obtained from 195 different patients who were admitted to our hospital for lower respiratory tract infections (81, exacerbation of chronic obstructive pulmonary disease; 114, pneumonia). The patients participated in an ongoing study in our hospital on the etiology of exacerbations of chronic obstructive pulmonary disease, a study approved by the local ethics committee. Samples were also collected from 34 patients after antibiotic treatment. The majority of the serum samples were obtained within 24 h of admission. Samples not immediately analyzed were stored at Ϫ80°C until analysis. PCT concentrations ranged from 0.02 g/L (limit of detection, i.e., the lowest concentration of analyte that can be reliably measured as being qualitatively present in the sample) to 57 g/L. PCT concentrations...

Analytical evaluation of the performances of Diazyme and BRAHMS procalcitonin applied to Roche Cobas in comparison with BRAHMS PCT-sensitive Kryptor

“…Different to the PCT-D, the comparison between PCT-BR and PCT-BK shows, as expected by previously published data [23], a very good correlation as appears from the Figure 3A and B and from the level of agreement indicated in Table 2. The small underestimation of PCT-BR (slope 0.912), very similar to the one reported by the manufacturer [18], explains the <100% agreement between the two methods (see Tables 2 and 3).…”

Method for the Selective Measurement of Amino-Terminal Variants of Procalcitonin

“…Key to the achieved high selectivity has been the development and selection of new monoclonal antibodies by targeting specific epitopes. Precision and reproducibility of the assays are comparable to other PCT assays (23,25,26 ). Whether the analytical sensitivity of the new PCT assays is sufficient for clinical use can only be fully answered after measurements are made in large sample cohorts; however, early data regarding detectability of PCT1-116 and PCT3-116 in human experimental endotoxemia indicate that the sensitivity might be suitable for most if not all indications that can be assessed by today's state-of-the-art PCT assays.…”

“…In both assays, all measured concentrations were below the functional assay sensitivities, i.e., Ͻ5 pmol/L for PCT1-116 and Ͻ1.3 pmol/L for PCT3-116, except for 4 concentrations measured for PCT3-116 (range 1.35-5.7 pmol/L). For current PCT assays in routine use today, measured concentrations in healthy subjects are also below the functional assay sensitivity (25,26 ).…”

Serum Procalcitonin and Peripheral Venous Lactate for Predicting Dengue Shock and/or Organ Failure: A Prospective Observational Study

“…The PCT assay using the Roche system in our study was previously evaluated for analytical performance in line with Clinical and Laboratory Standards. The PCT assay demonstrated acceptable precision, no evidence of nonlinearity, sample carryover or drift, and achieved high recovery from serum samples taken from patients with lower respiratory tract infections [46]. As the assay is marketed to reliably detect PCT concentrations as low as 0.02 ng/mL, the clinical laboratories providing testing are required to participate in regular international quality assurance programs to validate the test, particularly for standard hospital care.…”