Haematology and immunology
CD4 absolute count, cells/µL
Flow cytometry platform A (predicate) replaced by Flow cytometry platform B (new) (data set 2). 1,885 paired results.
Compare it with the other comparisons in the explorer
Comparison line
The new system reads 14.3% lower than the old system on average. The comparison line has a slope of 0.867 (95% interval 0.856 to 0.877) and an intercept of -1.2.
Fig. 1. The comparison line against the line of no change, over the range of the decision limits (100, 200, 350, 500 cells/µL). Dots mark where each line meets each limit; the gap between them is the bias at that limit.
Crossing each limit
Results that moved across a decision limit when the new system replaced the old, against the number repeat testing on one unchanged system would move. The program reports the count across all limits together.
All decision limits together (100, 200, 350, 500 cells/µL)
Crossed after the change: 535
Expected from repeat testing alone: about 238
Grade and warnings
- Re-test band: full (at least the protocol minimum of pairs).
- Band half-width around each limit: 5.51%.
- Results re-tested on data the band was not fitted to, median: 15%.
- Share of the excess crossings caught on unseen data, comparison line and band together: 66%; comparison line alone: 46%. The excess is the crossings above what repeat testing alone would cause, so the share can exceed 100% or fall below zero.
- Repeat-test imprecision: assumed, not measured at this site.
Source
Coetzee LM, Glencross DK (2017). PLoS One. doi:10.1371/journal.pone.0187456 (opens in a new tab); PMC5669480 (opens in a new tab) (title on the source page; it names the instruments). Licence: CC BY 4.0 (opens in a new tab). Changes: Paired results re-analysed by NakedSignal's program; instruments described generically; only derived results are shown. The deposit names the systems.
Show the numbers
| Field | Value |
|---|---|
| Paired results used | 1,885 |
| Comparison line slope | 0.866667 |
| Slope, 95% interval | 0.856122 to 0.877053 |
| Comparison line intercept | -1.2 |
| Mean difference, new minus old, as % of old | -14.284 |
| Decision limits (cells/µL) | 100, 200, 350, 500 |
| Crossed after the change | 535 |
| Expected from repeat testing alone | 238.49 |
| Band half-width (%) | 5.51 |
| Re-tested, unseen data, median (%) | 15.01 |
| Re-tested, unseen data, range (%) | 14.8 to 15.07 |
| Excess caught, line and band (%) | 66.23 |
| Excess caught, line alone (%) | 45.53 |