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Classify pre-to-post change against MDC and MCID thresholds

Source: R/change-annotate.R
annotateChange.Rd

Annotates a set of paired (pre, post) outcome scores against their Minimal Detectable Change (MDC) and Minimal Clinically Important Difference (MCID) thresholds, classifying each change as "no change" (within measurement error), "detectable (>MDC)" (a real change that clears measurement error) or "clinically meaningful (>MCID)". Thresholds are compared to the absolute change and are boundary-inclusive (a change exactly equal to the MDC is "detectable"). The direction of benefit is tracked separately so decrease-is-good metrics (pain, timed tests) are handled correctly.

Usage

annotateChange(pre, post, mdc, mcid, direction = "increase")

Arguments

pre, post

Numeric vectors of pre- and post-intervention scores (one element per metric); may be named to label the metrics.

mdc, mcid

Numeric MDC / MCID thresholds (positive), a scalar recycled across metrics or a vector matching pre. Obtain the MDC from PhysioCore::mdc() (or PhysioMoCap::mdc()); the MCID is the instrument's anchor-based value.

direction

Benefit direction, "increase" (higher is better, default) or "decrease" (lower is better); a scalar applied to all metrics or a vector matching pre.

Value

A data.frame of class "change_annotation" with columns metric, pre, post, change (signed post - pre), improvement (signed so positive = beneficial), mdc, mcid, exceeds_mdc, exceeds_mcid, improved, direction and classification. A metric with a missing pre or post yields NA change and classification: missingness is propagated rather than silently reported as "no change".

References

de Vet HCW et al. (2006). Minimally important change determined by a visual method. Qual Life Res; Shrout & Fleiss (1979) for the SEM underlying MDC.

See also

plotChangeAnnotated(), PhysioCore::mdc()

Examples

annotateChange(pre = c(fma = 20, pain = 7),
               post = c(fma = 31, pain = 4),
               mdc = c(5.2, 1.0), mcid = c(9, 2),
               direction = c("increase", "decrease"))
#> <change_annotation> 2 metric(s)
#>  metric change mdc mcid                classification
#>     fma     11 5.2    9 clinically meaningful (>MCID)
#>    pain     -3 1.0    2 clinically meaningful (>MCID)