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

INTRODUCTION: 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.
DISCUSSION AND CONCLUSION: Unsatisfactory sigma levels for BNP tests were achieved using both methods of calculating sigma metrics.