Sigma Metric Analysis
An ADVIA 2120i in Vietnam
A recent study of the ADVIA 2120i hematology analyzer in Vietnam used the 2014 Ricos goals to assess quality. What if the CLIA 2025 goals were applied instead?
An ADVIA 2120i in Vietnam
May 2026
Sten Westgard, MS
[Sigma quality score: +0.5 for control levels at medical decision levels (abnormal, normal); +0.5 bias measured over long term period (six months EQA); +1 EQA used for bias determination; +0.5 imprecision over long term (6 months). Final score: 2.5 = Between Optimistic and Moderate.]
A recent study from the Phuong Chau International Hospital in Can Tho City, Vietnam, examined the performance of the ADVIA 2120i hematology analyzer:
Application of Six Sigma Method Evaluating the Quality of Peripheral Blood Cell Testing at Phuong Chau International Hospital. Vo Thanh Tri, Bui Thuy An, Le Trung Tin, Le Phuoc Loi, Nguyen Thi Bao Ha. Journal of Health and Aging 2025;1(5):100-105.
Calculating Sigma metrics from routine laboratory performance data.
The imprecision and bias of the analyzers
"2196 IQC results" were collected over a six-month period from April to December 2024. Bias was determined from "six months of EQA results." The study authors used the 2014 Ricos database and the CLIA 1992 goals to benchmark the analytical quality of 4 hematology parameters. We decided to update the goals being used to the updated CLIA 2025 requirements.
| ADVIA 2120i parameter | TEa Source | TEa | % Bias | CV | Sigma |
| Hemoglobin | CLIA 2025 | 4.0 | 0.8 | 1.9 | 1.68 |
| Hemoglobin | 4.0 | 0.8 | 1.5 | 2.13 | |
| Hemoglobin | 4.0 | 0.8 | 1.2 | 2.67 | |
| Platelets | CLIA 2025 | 25 | 3.50 | 4.40 | 4.89 |
| Platelets | 25 | 3.50 | 2.70 | 7.96 | |
| Platelets | 25 | 3.50 | 2.50 | 8.60 | |
| RBC | CLIA 2025 | 4 | 1.50 | 1.30 | 1.92 |
| RBC | 4 | 1.50 | 1.70 | 1.47 | |
| RBC | 4 | 1.50 | 1.60 | 1.56 | |
| WBC | CLIA 2025 | 10 | 1.30 | 2.80 | 3.11 |
| WBC | 10 | 1.30 | 2.30 | 3.78 | |
| WBC | 10 | 1.30 | 2.80 | 3.11 |
Of the 4 parameters, only platelets are performing well, at Six Sigma. WBC is at the bare minimum acceptable quality. RBC and Hemoglobin are performing below 3 Sigma, which under normal circumstances would be considered unacceptable quality.
Graphic Display of performance by Normalized Method Decision Chart (NMEDx)
The updated CLIA goals are pretty harsh. Only 1 of the 4 parameters is doing well. The others are either unacceptable or hitting the bare minimum of quality.
Based on the older goals, the authors then applied the Westgard Sigma Rules to design QC around the lowest Sigma metrics of each parameter:
- WBC: 1:3s/2of3:2s/R:4s/3:1s, N=3, R=1
- RBC: 1:3s/2of3:2s/R:4s/3:1s/6:x, N=3, R=2 (2 runs per day)
- HGB: 1:3s/2of3:2s/R:4s/3:1s/6:x, N=3, R=2 (2 runs per day)
- PLT: 1:3s/2of3:2s/R:4s/3:1s N=3, R=1
If we apply the CLIA 2025 goals, the QC recommendations are slightly different:
- WBC: 1:3s/2of3:2s/R:4s/3:1s/6:x, N=3, R=2
- RBC: 1:3s/2of3:2s/R:4s/3:1s/6:x, N=3, R=2
- HGB: 1:3s/2of3:2s/R:4s/3:1s/6:x, N=3, R=2
- PLT: 1:3s/2of3:2s/R:4s N=3, R=1
Using CLIA 2025's goals, we see that 3 of the parameters need the maximum Westgard Rules (and actually more than that), but the platelet method needs fewer QC.
Conclusion
The authors of the study concluded: "These findings demonstrate that the Six Sigma approach is effective in monitoring and improving test quality by enabling the selection of appropriate IQC strategies for each parameter."
Through the lens of CLIA 2025 goals, we see that the ADVIA 2120i is challenged to meet modern performance demands. In order to use this instrument, the laboratory must expend additional effort in implementing more rules and potentially more controls and more runs. The CLIA 2025 hematology goals seem to be particularly demanding, there are few examples we've seen of today's instrumentation successfully achieving high Sigma-metrics for multiple parameters.