Risk analysis and assessment based on Sigma metrics and intended use

Abstract

Introduction: In order to ensure the quality in clinical laboratories and meet the low risk requirements of patients and clinicians, a risk analysis and assessment model based on Sigma metrics and intended use was constructed, based on which differential sigma performance (σ) expectations of 42 analytes were developed.

Materials and methods: Failure mode and effects analysis was applied to produce an analytic risk rating based on three factors, each test of which was graded as follows: 1) Sigma metrics; 2) the severity of harm; 3) intended use. By multiplying the score of Sigma metrics by the score of severity of harm by the score of intended use, each was assigned a typical risk priority number (RPN), with RPN ≤ 25 rated as low risk. Low risk was defined as acceptable standards; the sigma performance expectations were calculated.

Results: Among the 42 analytes, tests with σ ≥ 6, 5 ≤ σ < 6, 4 ≤ σ < 5, 3 ≤ σ < 4, σ < 3 were 21, 5, 5, 6, and 5, respectively; there were 7 high-risk tests, 8 of them medium risk tests. According to the risk assessment conclusion, 13 tests had sigma performance expectations ≥ 6; 15 test items had sigma performance expectations ≥ 5, while 3 test items had sigma performance expectations ≥ 4; 11 test items had sigma performance expectations ≥ 3.

Conclusions: Constructing the risk analysis and assessment model based on Sigma metrics and intended use will help clinical laboratories to identify the high-risk tests more objectively and comprehensively. Such model can also be used to establish the sigma performance expectations and meet the low risk requirements of patients and clinicians.

Keywords: Sigma metrics; Six Sigma; failure mode and effects analysis; risk analysis; risk assessment.

Figure 1

Normalized method decision chart demonstrating the Sigma metrics. ALT - alanine aminotransferase. AST - aspartate aminotransferase. ALP - alkaline phosphatase. GGT - gamma-glutamyltransferase. TP - total protein. ALB – albumin. BT – bilirubin, total. BD – bilirubin, direct. CREA – creatinine. UA - uric acid. Glc – glucose. CK - creatinine kinase. LD - lactate dehydrogenase. AMY – amylase. TG – triglycerides. CHOL - cholesterol. HDL – high density lipoprotein. LDL – low density lipoprotein. K – potassium. Na – sodium. Cl – chloride. Ca – calcium. Mg – magnesium. Phos – inorganic phosphate. Fe – iron. TRSF - transferrin. IgG – immunoglobulin G. IgM – immunoglobulin M. IgA – immunoglobulin A. PA - pre-albumin. Cys-C - cystatin C. BMG - ß2-microglobulin. C3 – complement C3. C4 – complement C4. CRP - C-reactive protein. cTn-I – cardiac troponin I. cTn-T – cardiac troponin T. pH – acidity. pCO2 - partial pressure of carbon dioxide. pO2 - partial pressure of oxygen. HbA1c – glycated haemoglobin.