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Change explorer · Chemistry

Point-of-care creatinine in venous blood vs a Jaffe laboratory analyser

Public dataBuilt from a published open-access study.

Central lab serum analyser, kinetic Jaffe compared with point of care analyser, venous whole blood: 89 paired results from a published study by Krisher et al. (2024), re-analysed by NakedSignal as if one laboratory had switched from the first system to the second. At 1.2, 1.5 mg/dL, 1 results fall in a different category on the second system than on the first, against about 1 expected from repeat testing alone. Here the count sits below the repeat-testing expectation, but that expectation uses a default repeat-test imprecision, which can overstate repeat-testing noise, and the count cannot be told apart from what repeat testing alone would move, so it is not evidence of fewer than noise. A laboratory’s own measured imprecision decides.

Chemistry

Creatinine, mg/dL

Central lab serum analyser, kinetic Jaffe compared with Point of care analyser, venous whole blood. 89 paired results.

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Comparison line

The new system reads 0.6% lower than the old system on average. The comparison line (Passing-Bablok) has a slope of 1.429 (95% interval 1.25 to 1.667) and an intercept of -0.343.

Public data
Comparison line, creatinine (mg/dL)Comparison line with slope 1.429 (95% interval 1.25 to 1.667) and intercept -0.343, drawn against the line of no change. Decision limits drawn at 1.2, 1.5 mg/dL. Where the comparison line sits above the line of no change, the new system reads higher; below, lower.0.511.5211.51.21.5No changeComparison lineOld system, mg/dLNew system, mg/dL

Fig. 1. The comparison line against the line of no change, over the range of the decision limits (1.2, 1.5 mg/dL). 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 (1.2, 1.5 mg/dL)

Crossed between the two systems: 1

Expected from repeat testing alone: about 1

Grade and warnings

  • Re-test band: Indicative: 89 pairs, below the 100-pair protocol minimum.
  • Band half-width around each limit: 27.66%.
  • Results re-tested on data the band was not fitted to, median: 12%.
  • Repeat-test imprecision: default value.
  • Note: Fewer than 5 results crossed beyond what repeat testing alone would move; excess caught is not meaningful here.

Source

Krisher L, Jaramillo D, Dye-Robinson A, Dally M, Butler-Dawson J, Brindley S, Pilloni D, Cruz A, Villarreal Hernandez K, Schaeffer J, Adgate JL, Newman LS (2024). Application and comparison of point-of-care devices for field evaluation of underlying health status of Guatemalan sugarcane workers. PLOS Glob Public Health. doi:10.1371/journal.pgph.0003380 (opens in a new tab); PMC11265697 (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
All values for creatinine, Central lab serum analyser, kinetic Jaffe to Point of care analyser, venous whole blood
FieldValue
Paired results used89
Comparison line slope1.428571
Slope, 95% interval1.25 to 1.666667
Comparison line intercept-0.342857
Mean difference, new minus old, as % of old-0.556
Decision limits (mg/dL)1.2, 1.5
Crossed between the two systems1
Expected from repeat testing alone1.25
Band half-width (%)27.66
Re-tested, unseen data, median (%)12.36
Re-tested, unseen data, range (%)12.36 to 13.48
Excess caught, line and band (%)none
Excess caught, line alone (%)none

Related

Other comparisons from the same study:

Guide: Jaffe or enzymatic creatinine

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