Application of Six Sigma Metrics to Improve Quality Control for Point-of-care Glucose Testing

Objectives: Six sigma is a quality management system for the assessment of precision and accuracy. We aim to apply the six sigma rule to quality control (QC) of point-of-care (POC) glucose meters in a tertiary hospital. Methods: Thirty POC glucose meters installed at Ewha Womans University Mokdong Hospital were monitored between January 2013 and March 2014. The QC data from the POC glucose meters at low and high levels were collected. The monthly mean, standard deviation, bias, coefficient of variation, and mean sigma metrics were calculated. The correlation between accuracy and precision was assessed based on the percentage bias and coefficient of variation. Comprehensive instructions on the QC and maintenance of the devices were provided in the departments with poor sigma scores. A follow-up assessment was performed after the intervention. Results: The mean sigma values for the low and high controls were 3.29 and 3.71, respectively. At the low and high controls, 36.6% and 10% of the glucose meters showed a sigma value <3. The causes of low sigma values included the use of expired control materials, prolonged air exposure of the sample strip, lack of user training, and errors in device maintenance. On follow-up monitoring for 3 months following QC intervention, 23.3% (low control) and 6.6% (high control) of the glucose meters scored a sigma value <3, indicating improved QC. Conclusion: Sigma metrics-based QC can successfully improve accuracy and precision of POC glucose meters in an objective and quantitative manner and can be used for follow up after QC intervention. (Ewha