Peer-review started: January 4, 2018
First decision: January 23, 2018
Revised: January 30, 2018
Accepted: February 6, 2018
Article in press: February 6, 2018
Published online: March 18, 2018
Newly developed patient-reported outcomes have many advantages, but require further studies, including establishing minimum clinically important difference (MCID) values. Determining the MCID for the Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS® PF) will be useful for orthopaedic clinical practice and it is helpful to understand the MCID in the context of previously used measures like the hip disability and osteoarthritis outcome score for joint reconstruction (HOOS JR), and the knee injury and osteoarthritis outcome score for joint reconstruction (KOOS JR), Anchor-based and distribution-based methods can both be used to determine MCID.
New instruments require studies to inform their score interpretation. Because of the lack of consensus on MCID methods, a comprehensive approach was taken, using both anchor- and distribution-based methods at multiple levels of precision and multiple follow-up time points. Cross verification of MCID values using powerful triangulation methods allow researchers and clinicians to understand the complexity of MCID evaluation and conscientiously select the most appropriate one for themselves.
To determine MCIDs for the PROMIS PF, HOOS JR and KOOS JR in a general joint orthopaedic patient population applying comprehensive methods.
Consecutively enrolled patients aged 18 and older from a large academic orthopaedic joint clinic completed PROs at their first clinic visit and at follow-up points from 3-mo to 6-mo and beyond. These patients also completed an anchor question that queried how much their physical function had improved since their first clinic visit. They were grouped into change and no-change categories. Anchor-based analyses looked at mean change scores and the receiver operating curve to maximize the best cut-off based on sensitivity and specificity. Distribution-based analyses looked at the standard deviation, and minimum detectable change.
There were 2226 patients who participated with a mean age of 61.16 (SD = 12.84) years, 41.6% male, and 89.7% Caucasian. Mean change ranged from 7.29 to 8.41 for the PROMIS® PF CAT; from 14.81 to 19.68 for the HOOS JR; and from 14.51 to 18.85 for the KOOS JR. ROC cut-offs ranged from 1.97-8.18 for the PF CAT, 6.33-43.36 for the HOOS JR, and 2.21-8.16 for the KOOS JR. Distribution-based methods estimated MCID values ranging from 2.45 to 21.55 for the PROMIS® PF CAT; from 3.90 to 43.61 for the HOOS JR; and from 3.98 to 40.67 for the KOOS JR. The median MCID value in the range was similar to the mean change score for each measure and was 7.9 for the PF CAT, 18.0 for the HOOS JR, and 15.1 for the KOOS JR.
Overall this study identified a large range of MCIDs for the PROMIS® PF, HOOS JR, and KOOS JR in an orthopaedic sample of patients with joint ailments. This range reflects the comprehensive strategies applied to determine MCIDs at varying levels of precision and cut off standards. The range of MCIDs presented in this study can be incorporated into decision making to guide treatment recommendations, compute sample size for research studies and clinical trials, and conduct respondent analyses.
Decisions on which MCID value to select or which MCID value is useful should be based on an individual’s personal value and belief. Future research direction should focus on investigation of MCIDs with a more diverse demographic sample and to link MCIDs with baseline scores using Rasch-based methods.