Quality Standards

Can the biochemistry assays on a DxC 700 in India hit the new measurement uncertainty goals?

18 of 25 assays on a DxC 700 in an Indian Lab can meet uncertainty goals

Sten Westgard, MS
February 2025

A recent study in the looked at a laboratory in Dehradun, India and the performance of the Beckman Coulter DxC 700 for both cc and ia assays. For the most part the study used the latest measurement uncertainty goals, but in a few cases they used MAu goals even when new measurement uncertainty goals were available. In our analysis here, we will confine ourselves to the assays that have the new mu goals and use them exclusively for assessment.

Evaluation of Measurement Uncertainty in Clinical Chemistry and its Comparison With Analytical Performance Specifications. Wadhwa N, Bhat K, Kalsi M. et al. (February 15, 2025) Cureus 17(2): e79043. DOI 10.7759/cureus.79043

The CV information comes from BioRad controls run daily from January to December 2023, so we have a long term estimation of imprecision. This study is unique in that it not only calculated u:Rw, it also calculated u:cal (information supplied by the manufacturer), and the final u:result. It did not include bias, as "Unity RealTime software... indicated that none of the measurands exhibited medically significant bias." We'll leave that statement for now.

[Full disclosure: Beckman Coulter is a strategic consulting partner of Westgard QC, Inc. The study being analyzed in this article was independently conducted. See all of our consulting partnerships here.]

The short answer: 18 of 25 assays can meet the desirable measurement uncertainty goals.  This is definitely the most promising result of our uncertainty analyses thus far. Some of the numbers here, with u:Rw as less than 0.1, are numbers we've never encountered before. Seeing similar performance in additiona studies would be helpful to confirm that this performance is not an isolated case.

 Of course, this is not taking into account any bias that might be present. As noted earlier, the study found no significant biases present. What was considered a significant bias? It would be better to have listed the biases that were measured so the significance can be judged by all. Some of the analytes that passed here might not, if bias was included.

We do see that there are a few cases where the u:Rw was unacceptable, but the overall u:Result was still acceptable. That's a result of the u:ref and u:cal taking up less than the standard 50% of the uncertainty budget.

Other examples have shown that the new mu goals are too demanding, but this example raises the possibility that there some instruments are better positioned to succeed in the new mu world than others. Further analyses are needed to determine if any of this performance is reproducible.