Estimating minimal important change of the National Institutes of health research task force impact score using computer adaptive measures: a secondary analysis of two randomized clinical trials in a military population with chronic pain
Authors: Flynn Diane M. , Burke Larisa A. , Steffen Alana D. , Ransom Jeffrey C. , Orr Kira P. , McQuinn Honor M. , Snow Tyler J. , Doorenbos Ardith Z. 
Published: February 2025

Abstract

Background
The National Institutes of Health (NIH) Research Task Force (RTF) on Research Standards for Chronic Low Back Pain impact score is a composite measure of Patient Reported Outcomes Measurement Information System (PROMIS) pain intensity, pain interference and physical function. PROMIS surveys are available in short-form and computer adaptive testing (CAT) formats. Minimal important change (MIC) can be estimated to determine if between-group differences are large enough to be important. To date, three anchor-based estimates of impact score MIC ranging from 3 to 7.5 have been published, and all were based on data collected using PROMIS short-form surveys. None used CAT versions of PROMIS surveys.

Methods
Secondary analysis of data collected during the conduct of two randomized clinical trials of 6-week courses of nonpharmacological pain therapies. Research subjects were US active-duty service members referred to an interdisciplinary pain management center. Impact score was assessed at the beginning and end of treatment. The Patient Global Impression of Change (PGIC) questionnaire was administered at the end of treatment and asked respondents to report their status compared to the start of treatment using a 7-item categorical scale ranging from very much improved to very much worse. A PGIC response of “much” or “very much” improved defined important improvement. Receiver operating characteristic (ROC) curve analysis and predictive logistic regression models were used to estimate MIC for the full combined sample and stratified by study sample and baseline impact score. Measures of individual statistical change were also computed.

Results
Overall, a decrease of 3 points in impact score was the estimated MIC (2.5 for ROC analysis and 3.4 for predictive modeling approach). Larger decreases in impact score were needed for participants with moderate and severe baseline pain impact to report important improvement. Thresholds for individual statistically significant change ranged from 6 to 14.

Conclusions
Using data collected with CAT surveys, we calculated an MIC of 3 points for the NIH RTF impact score, and estimates ranged from 1.3 to 7.2 depending on the baseline impact score and statistical approach used. These findings are consistent with previous MIC estimates that were based on non-adaptive short form surveys and have implications for improving the accuracy of pain treatment response assessment.

Registry information
Trial registration. ClinicalTrials.gov. Registry numbers: NCT03297905 (registered 9/29/17) and NCT04656340 (registered 11/30/20). Link to full applications: https://classic.clinicaltrials.gov/ct2/show/NCT03297905?titles=Determinants+of+Optimal+Dosage%26cntry=US%26draw=2%26rank=1; https://classic.clinicaltrials.gov/ct2/show/results/NCT04656340?titles=Complementary+and+Integrative+pain+therapies+and+functional+restoration+%28IMPPPORT%29%26draw=2%26rank=1. Patient enrollment dates: SMART: 17 March 2021, prospectively registered; IMPPPORT: 9 December 2015, retrospectively registered.