Diagnostics makers and EQA schemes
A neutral count of what a conversion does to patients.
When a laboratory moves to a new analyser or reagent, we show its director what changes at their own limits, measured the same way whoever asks.
What you get
Conversions planned, not argued about
One method for makers, laboratories and schemes, so every party reads the same numbers.
Makers: point the laboratory to the check
Laboratory directors hold a switch until they know what it does to their patients.
Makers can point a laboratory to the change check or the report. The laboratory commissions it, owns it and sees it first. We take no payment from a maker for a report on a laboratory's change.
Neutral by design
A maker's own numbers carry less weight with the laboratory deciding.
The same method, limits and wording for every laboratory: bias at its own limits, crossings against repeat testing, and a re-test band for the transition. We take no payment from a model or analyser maker for a test we run for a third party.
EQA: the changes participants declare
Schemes see results move when participants change analyser, reagent or software.
A study the scheme runs on its own systems: each declared change is sized against participants that did not change, with a check for regression to the mean set before any scheme data are read. So far it has been shown on synthetic data only. The scheme runs the code on its own computers, reviews the output and decides what, if anything, is released or published. By default a kind of change is shown only if at least 10 participants made it; the scheme may keep, tighten or set this aside. A study with a scheme carries no fee either way.
See it on real data
The count depends on the laboratory’s own precision
Fig. 1 is a public comparison of two creatinine methods. That expected count uses the 1.8% imprecision the study itself measured; at that imprecision the count from repeat testing alone falls between 6 and 17 with 95% probability, so the 23 crossings are about twice the expected count, and by the exact Poisson-binomial test 23 or more from repeat testing alone has probability 0.00017. The report says which imprecision it used, and a laboratory’s report uses its own.
- public method comparisons analysed
- 34
- published studies
- 12
- paired results analysed
- 10,579
Creatinine at 1.2, 1.5 mg/dL
Crossed between the two systems: 23
Expected from repeat testing alone: about 12
Fig. 1. Enzymatic and kinetic Jaffe creatinine run on the same 529 samples on one central-lab analyser, read as a switch from enzymatic to Jaffe. 23 results changed category at the decision limits, against about 12 (95% range 6 to 17) expected from repeat testing alone at the 1.8% imprecision the study measured. That 1.8% is also our program's laboratory-analyser default (1.79%, this study's own reported precision), so the default gives about the same count; the program's cautious point-of-care default of 6%, which it uses when a point-of-care device is involved and no precision data are supplied, would give about 41, which overstates repeat-testing noise for these laboratory analysers. The guide to Jaffe and enzymatic creatinine gives the detailed figures.
Source Schmidt RL, Straseski JA, Raphael KL, Adams AH, Lehman CM (2015). A Risk Assessment of the Jaffe vs Enzymatic Method for Creatinine Measurement in an Outpatient Population. PLoS One. doi:10.1371/journal.pone.0143205 (opens in a new tab); PMC4657986 (opens in a new tab). Licence: CC BY 4.0 (opens in a new tab). Re-analysed by NakedSignal. Open this comparison in the explorer.
Show the numbers
| Measure | Value |
|---|---|
| Paired results | 529 |
| Decision limits (mg/dL) | 1.2, 1.5 |
| Results that fall in a different category on the second system | 23 |
| Expected to change from repeat testing alone | 11.67 |
| Mean difference, new minus old, as % of old | 0.34 |
| Repeat-test imprecision | Supplied by the study |
How it works
How a laboratory's change is checked
The laboratory asks
A laboratory planning a change asks for the check or the report itself. A maker may point it to us, but does not commission or pay for it.
The laboratory runs it
The program runs on the laboratory's own computer, on the paired results from its method comparison.
Each party gets its view
The laboratory gets its full report and decides what, if anything, it shares. Results pooled across laboratories are aggregates, designed to carry no patient row; each laboratory signs off what is released.
Guides
Go deeper
- GuideReagent lot changesWhy a new reagent or calibrator lot can shift patient results that QC does not show, what CLSI EP26 asks, where it leaves gaps, and how to judge a small comparison at decision limits.
- GuideJaffe or enzymatic creatinineWhy Jaffe and enzymatic creatinine differ, what IDMS traceability fixes and what it does not, and how many results a method or device change moves across a line, on five public comparisons.
- GuideComparability across analysers and sitesWhat ISO 15189:2022 and CLSI EP31 ask when one test runs on more than one instrument, and how to report comparability at decision limits, with public data from three meters in two settings.
Planning conversions, or holding scheme data?
Tell us what is changing and where. We will show you what the count would measure.