10 of 27 analytes on a Cobas Pure cannot hit desirable MAU

I came across a rare but intriguing study of measurement uncertainty recently:

Standardized Estimation of Measurement Uncertainty in Clinical Chemistry Using ISO 20914. Mohammad I. Ahmad, Fayha S Ahmed, Deepa Rao, Mohamedi Begum, Sheifa Joan. Clin Lab 2026;72:1-6. https://www.clin-lab-publications.com/article/5788

The study looked at 27 general biochemistry analytes on the Roche Cobas Pure analyzer, this at the Nad al Hammar Health Center, Dubai Health, Dubai. The EFLM biological database was used to compare the lab's observed mu against the desirable MAU (maximum allowable uncertainty).

The key takeaway: "10 analytes - including albumin, alkaline phosphatase, calcium, magnesium, phosphorous, transferrin, troponin T hs, uric acid, urine albumin, and vitamin D - exceeded the desirable MAU limits..."

Now this study measured two levels of performance for each analyte, so the failure rate is not 10/27, but rather 10/54. Nevertheless, a failure rate of 18.5% is not a good look for a new analyzer.

As with the TEa goals from the EFLM, the solution proposed by the database is to judge the allowable uncertainty at a more forgiving level. If you switch to using minimum MAU, the failures drop down to "just" 7/54. A failure rate of 12.9%. However some of those remaining methods are extremely uncertain:

The EFLM minimum MAU for troponin T hs is 17.1%. This lab has a mu of 197.94%!
The EFLM minimum MAU for uric acid is 12.1%. This lab has a mu of 25.01%!
The EFLM minimum MAU for urine albumin is 15.5%. This lab has a mu of 47.46%!
The EFLM minimum MAU for phosphorous is 11.6%. This lab has a mu of 50.49%!
The EFLM minimum MAU for magnesium is 4.1%. This lab has a mu of 94.67%!
The EFLM minimum MAU for vitamin D is 10.2%. This lab has a mu of 26.81% at the low level and 14.42% at the high level.

When your magnesium has 23X the minimum MAU, that's something to investigate...

P.S. If you put these failures rates on the Six Sigma scale, this Cobas Pure is operating at 2.3 Sigma in achieving desirable MAU, and 2.6 Sigma in achieving minimum MAU.