Evaluation of Sigma value and quality goal index for brain natriuretic peptide test

Abstract

Evaluation of sigma value and quality goal index for brain natriuretic peptide test T he b-type or brain natriuretic peptide (BNP) is a member of the natriuretic peptide family that is involved in many biological events in the body, including regulation of blood pressure and blood volume [1][2][3]. BNP is mainly synthesized in the cardiac ventricle as proBNP, which is a prohormone consisting of 108 amino acids. ProBNP is cleaved in the circulation as an active hormone 32 amino acid structure that corresponds to the C-terminus of proBNP. The N terminal (NT) 76 amino acid NT-proBNP is an inactive protein. Both BNP and NT-proBNP have a wide range of clinical effects that increase cardiac stress and output [1][2][3]. Measurement of BNP levels to differentiate the causes of acute dyspnoea in patients admitted to the emergency de-partment has high diagnostic accuracy [3,4]. Heart failure (HF) is unlikely when the plasma BNP level is <100 pg/ml, and a level higher than 400 pg/ml is appropriate for ruling in acute HF, which makes it a suitable test for patient identification in emergency care settings [1][2][3][4]. However, recent studies suggested that there are significant differences in analytical performance among commercial methods for BNP immunoassays [5] An erroneous result, in which the difference between a test result and the corresponding true value exceeds the allowable total error (Tea), leads to medically significant errors. To improve patient safety, zero errors should be targeted in health services that cannot be possible in a real laboratory setting [6].Objectives: In this study, we aimed to evaluate the analytical process by determining the sigma values and quality goal index (QGI) of the brain natriuretic peptide (BNP) test parameter performed in our emergency laboratory. Methods: BNP levels were tested using a commercially available immunoassay autoanalyser (Advia Centaur XP; Siemens Healthcare Diagnostic Ltd., Muenchen, Germany). Bias was calculated by comparison with the group mean for each external quality assessment report, and an internal quality control-based approach was applied. The internal quality control results of the BNP test levels between September and December 2018 and external quality program reports were used in the coefficient of variation (CV) and bias calculations. The sigma metrics and QGI were calculated. Results: The sigma metric calculated from the external quality control was 2.1 and the QGI was 0.34. In the internal quality control study, the sigma level was 1.92, and the QGI was 0.55, as calculated at the 400 pg/ml level. The QGI level suggests that the problem in the BNP study was imprecision. Conclusion: Unsatisfactory sigma levels for BNP tests were achieved using both methods of calculating sigma metrics.