Sigma Metric Analysis

A recent study looked at the analytical performance of a Sysmex XN-1000 in Karnataka, India.  We benchmark the numbers against the CLIA 2025 guidelines. 

A Sysmex XN-1000 in Bengaluru, India

January 2026
Sten Westgard, MS

A recent study from the Vydehi Institute of Medical Sciences and Research Institute in Bengaluru, Karnataka, India, evaluated the performance of the main hematology parameters on a Sysmex XN-1000: 

Application of Six Sigma Metrics to Analyzer the Performance of Internal Quality control in Hematology Laboratory. Selvi NT, Kavya N, Gain D, Radha K. J Datta Meghe Inst Med Sci Univ 2025;20:818-23.

Calculating Sigma metrics from routine laboratory performance data.

[If you need a refresher on Sigma-metrics, check that out here. In this current section of the website, there are hundreds of real-world examples to review.]

The imprecision and bias of the analyzers:

Imprecision was calculated monthly for 6 months, 3 levels from Bio-Rad. "Monthly IQC runs of all 3 levels of minimum 60 runs were inclued for the given month of this study." Bias was calculated comparing the lab mean vs the target mean. The study looked at Sigma metrics for each month. In our analysis, we're taking a cumulative of all 6 months, so a longer term view. Single month metrics will have ups and downs, but a longer cumulative assessment will have less turbulence. 

The study applied the CLIA 1992 performance goals, so in our assessment we used the more relevant CLIA 2025 performance goals. These are particularly challenging, and significantly smaller than the 1992 goals.

Graphic Display of performance by Normalized Method Decision Chart (NMEDx)

Over half of the performance on this instrument is 3 Sigma or below. Very few parameters achieve Six Sigma, and none across all levels.  For an actual imlementation of these metrics, we would have to choose which level for each parameter is most important, and design QC around that. It might mean that a very minimal QC design is necessary, such as 1:3s with N=3, while other analytes may need the full Westgard Rules. 

For the study as calculated, using the 1992 CLIA goals, "the average of all parameters comes under an acceptable range, the same IQC that has been followed in our laboratory that is running all 3 levels of IQC with the frequency of twice a day will be continued." In our recalculations, with updated goals and averaged performance, the rules will vary by analyte. Sigma-metrics could be used to determine the QC frequency, but that's a bit challenging to implement. If we have one analyte at 6 Sigma, and one at 3 Sigma, you'll have recommendations for QC once every 1,000 patients and for QC once every 45 patients. What will you choose if one control covers both these analytes?

Conclusion

This Sysmex XN-1000 in India has performance that can easily achieve the goals of 1992. Living up to the CLIA standards of 2025 is harder. We've seen few hematology instruements that can hit these new goals at a world class level, in India or anywhere else.