Performance evaluation of a coagulation laboratory using sigma metrics

Document Type



Pathology and Laboratory Medicine


Purpose: Two-thirds of medical decisions are based on laboratory test results. Therefore, laboratories should practice strict quality control (QC) measures. Traditional QC processes may not accurately reflect the magnitude of errors in clinical laboratories. Six Sigma is a statistical tool which provides opportunity to assess performance at the highest level of excellence. The purpose of this paper is to evaluate performance of the coagulation laboratory utilizing Sigma metrics as the highest level of quality.
Design/methodology/approach: Quality indicators of the coagulation laboratory from January 1, 2009, to December 31, 2015, were evaluated. These QIs were categorized into pre-analytical, analytical and post-analytical. Relative frequencies of errors were calculated and converted to Sigma scale to determine the extent of control over each process. The Sigma level of 4 was considered optimal performance.
Findings: During the study period, a total of 474,655 specimens were received and 890,535 analyses were performed. These include 831,760 (93.4 percent) routine and 58,775 (6.6 percent) special tests. Stat reporting was requested for 166,921 (18.7 percent). Of 7,535,146 total opportunities (sum of the total opportunities for all indicators), a total of 4,005 errors were detected. There were 2,350 (58.7 percent) pre-analytical, 11 (0.3 percent) analytical and 1,644 (41 percent) post-analytical errors. Average Sigma value obtained was 4.8 with 12 (80 percent) indicators achieving a Sigma value of 4. Three (20 percent) low-performance indicators were: unacceptable proficiency testing (3.8), failure to inform critical results (3.6) and delays in stat reporting (3.9).
Practical implications: This study shows that a small number of errors can decrease Sigma value to below acceptability limits. If clinical laboratories start using Sigma metrics for monitoring their performance, they can identify gaps in their performance more readily and hence can improve their performance and patient safety.
Social implications: This study provides an opportunity for the laboratorians to choose and set world-class goals while assessing their performance.
Originality/value: To the best of the authors' knowledge and belief, this study is the first of its kind that has utilized Sigma metrics as a QC tool for monitoring performance of a coagulation laboratory.

Publication (Name of Journal)

International Journal of Health Care Quality Assurance