According to the authors, this is the first study to approach methotrexate intolerance measurement from a patient perspective.
Researchers have developed a Patient‐Perceived Methotrexate Intolerance Scale (PPMIS) for use among adult patients with rheumatoid arthritis (RA) to measure methotrexate intolerance and describe its psychometric properties.
Methotrexate has been a primary RA therapy for over 30 years. However, like other RA treatments, efficacy and tolerance varies by patient and therefore requires medication adjustments over the treatment course.
According to the authors of the study, which was published in Musculoskeletal Care, this was the first study to approach methotrexate intolerance measurement from a patient perspective. Clinically, they said the scale can be utilized to identify patients with RA who are at risk of intolerance, as well as tailor treatments and overall improve patient satisfaction.
The PPMIS is an 18-item weighted scale, including 4 subscales:
The scale is patient-reported and consists of statements with most response options ranging from “strongly agree” to “strongly disagree,” or “extremely likely” to “not at all likely.”
“This study has not only developed a new scale with sound psychometric properties, it has expanded the perspective in which to consider the construct of methotrexate intolerance from the provider to the patient, a critically important step towards expanding patient‐centred research and improve patient‐centred care,” the authors said.
To develop the scale, the study was conducted in 3 phases. Phase 1 involved a literature review and individual interviews with 14 patients with RA. In Phase 2, 10 patients with RA supplied feedback on the scale’s readability and clarity, as well as its ability to measure methotrexate intolerance.
A larger sample of 204 patients with RA completed the scale during Phase 3, where the researchers developed the final version of the PPMIS and tested its validity, reliability, and ability to separate former and current patients using methotrexate.
The authors used Cronbach’s alpha to measure the validity, which ranged from 0.79 to 0.94 and is therefore considered an “acceptable” consistency, according to an International Journal of Medical Education publication. Various sources also consider this to be between a “good” and “excellent” consistency.
Based on intra‐class correlation coefficients, the test-retest reliability at 2 weeks ranged from 0.73 to 0.88. According to a Peer J publication, a score greater than 0.75 is considered “excellent.”
Additionally, the PPMIS was able to accurately differentiate between former and current users of methotrexate 77% of the time.
It should be noted that characteristics of the sample population may offer multiple limitations of this study. The study only included adults who spoke English and had access to a smartphone or both a telephone and Internet. The Phase 3 sample was predominantly female (87.7%) and White (87.1%), and most (40%) had a college education.
The scale also does not measure information on drug efficacy or prospectively measure methotrexate use; however it was validated using 2 evidenced‐based metrics.
“Future studies will benefit from prospectively measuring methotrexate intolerance and methotrexate efficacy, with particular emphasis on including a larger and more diverse sample,” the authors said. “An additional aim of future studies should be to determine the scale’s sensitivity to change over time towards the goal of developing interventions to improve methotrexate tolerance, reduce RA disease activity and enhance patient quality of life.”
The study was sponsored by Pfizer.
Salt E, Wiggins A, Lohr K, et al. The development and validation of a patient‐perceived methotrexate intolerance scale for use in adult rheumatoid arthritis patients. Musculoskeletal Care. Published online December 8, 2021. doi:10.1002/msc.1606