Haematology and immunology
CD4 absolute count, cells/µL
Flow cytometry platform A (predicate) compared with 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 (Passing-Bablok) has a slope of 0.867 (95% interval 0.857 to 0.878) 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 fall on the other side of a decision limit on the new system than on the old, read as if the new system had 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 between the two systems: 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: default value.
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). Licence: CC BY 4.0 (opens in a new tab). Re-analysed by NakedSignal. The deposit names the systems.
Show the numbers
| Field | Value |
|---|---|
| Paired results used | 1,885 |
| Comparison line slope | 0.866667 |
| Slope, 95% interval | 0.857137 to 0.878224 |
| Comparison line intercept | -1.2 |
| Mean difference, new minus old, as % of old | -14.284 |
| Decision limits (cells/µL) | 100, 200, 350, 500 |
| Crossed between the two systems | 535 |
| Expected from repeat testing alone | 238.49 |
| Band half-width (%) | 5.51 |
| Re-tested, unseen data, median (%) | 15.02 |
| Re-tested, unseen data, range (%) | 14.75 to 15.28 |
| Excess caught, line and band (%) | 66.1 |
| Excess caught, line alone (%) | 45.87 |