Concurrent validity and precision of the thumb disability examination (TDX) in first carpometacarpal osteoarthritis.
Leah Johnson, Ryan Karau, Corey McGee
PMID 34563444WHAT IT FOUND
In 16 adults with thumb CMC osteoarthritis, the TDX agreed with the bMHQ.
Total score changes above about 17 points on a 0 to 100 scale may reflect real change, but the pain subscale was less precise.
Key findings
01The TDX total score showed a high negative association with the bMHQ total score (r_s = -0.733; P = .001), with the negative sign reflecting opposite scoring directions.
02For the TDX total score, a change exceeding about 6 points can be 90% confident not attributable to error, and a change exceeding about 17 points can be 95% confident not attributable to error.
03The pain subscale had an MDC% greater than 30%, exceeding the acceptable measurement error threshold, so using it to measure treatment change should be done with caution.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study included only 16 participants, so the precision estimates may be unstable. Some participants were included after a positive pressure shear test rather than a confirmed medical record diagnosis. The results cannot be generalized to other populations or to settings where more than one therapist uses the TDX over time. The pain subscale exceeded the acceptable 30% measurement error threshold, so it should be used with caution for tracking change. The sample was primarily white, over age 65, and mostly graduate educated, which limits generalizability. The MDC% is usually calculated for samples greater than 30 participants, and a larger sample may lower the error estimates.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not read this as evidence that the TDX improves thumb pain or function. It tested how a questionnaire agrees with another questionnaire and how stable its scores are over 7 to 21 days in 16 people. The pain subscale should not be used alone to judge treatment change because its measurement error exceeded the acceptable threshold.