There is a new article in Clinical Chemistry about a complicated (to me) analysis of quality targets for A1c when it would seem that a simple error grid – prepared by surveying clinicians would fit the bill.
Thus, this paper has problems. They are:
- The total error model is limited to average bias and imprecision. Error from interferences, user error, or other sources is not included. It is unfortunate to call this “total” error, since there is nothing total about it.
- A pass fail system is mentioned, which is dichotomous and unlike an error grid which allows for varying degrees of error with respect to severity of harm to patients.
- A hierarchy of possible goals are mentioned. This comes from a 1999 conference. But there is really only one way to set patient goals (listed near the top of the 1999 conference): namely; a survey of clinician opinions.
- Discussed in the Clinical Chemistry paper is the use of biological variation based goals for quality targets. Someone needs to explain to me how this could ever be useful.
- The analysis is based on proficiency survey materials, which due to the absence of patient interferences (see #1) is a subset of total error.
- From I could tell from their NICE reference (#11) in the paper, the authors have inferred that total allowable error should be 0.46% but this did not come from surveying clinicians.
- I’m on-board with six sigma in its original use at Motorola. But I don’t see its usefulness in laboratory medicine compared to an error grid.