{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T19:29:47Z","timestamp":1792178987545,"version":"4.4.0"},"reference-count":25,"publisher":"The Journal of Rheumatology","issue":"1","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J Rheumatol"],"published-print":{"date-parts":[[2021,1,1]]},"abstract":"<jats:sec><jats:title>Objective.<\/jats:title><jats:p>Patients with dermatomyositis (DM) and polymyositis (PM) have reduced muscle endurance.<\/jats:p><jats:p>The aim of this study was to streamline the Functional Index-2 (FI-2) by developing the Functional Index-3 (FI-3) and to evaluate its measurement properties, content and construct validity, and intra- and interrater reliability.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods.<\/jats:title><jats:p>A dataset of the previously performed and validated FI-2 (n = 63) was analyzed for internal redundancy, floor, and ceiling effects. The content of the FI-2 was revised into the FI-3. Construct validity and intrarater reliability of FI-3 were tested on 43 DM and PM patients at 2 rheumatology centers. Interrater reliability was tested in 25 patients. The construct validity was compared with the Myositis Activities Profile (MAP), Health Assessment Questionnaire (HAQ), and Borg CR-10 using Spearman correlation coefficient.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results.<\/jats:title><jats:p>Spearman correlation coefficients of 63 patients performing FI-3 revealed moderate to high correlations between shoulder flexion and hip flexion tasks and similar correlations with MAP and HAQ scores; there were lower correlations for neck flexion task. All FI-3 tasks had very low to moderate correlations with the Borg scale. Intraclass correlation coefficients (ICC) of FI-3 tasks for intrarater reliability (n = 25) were moderate to good (0.88\u20130.98). ICC of FI-3 tasks for interrater reliability (n = 17) were fair to good (range 0.83\u20130.96).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion.<\/jats:title><jats:p>The FI-3 is an efficient and valid method for clinically assessing muscle endurance in DM and PM patients. FI-3 construct validity is supported by the significant correlations between functional tasks and the MAP, HAQ, and Borg CR-10 scores.<\/jats:p><\/jats:sec>","DOI":"10.3899\/jrheum.191374","type":"journal-article","created":{"date-parts":[[2020,4,15]],"date-time":"2020-04-15T16:37:38Z","timestamp":1586968658000},"page":"94-100","source":"Crossref","is-referenced-by-count":25,"title":["Functional Index-3: A Valid and Reliable Functional Outcome Assessment Measure in Patients With Dermatomyositis and Polymyositis"],"prefix":"10.3899","volume":"48","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5975-3830","authenticated-orcid":false,"given":"Floranne C.","family":"Ernste","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1655-3382","authenticated-orcid":false,"given":"Christopher","family":"Chong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5847-7475","authenticated-orcid":false,"given":"Cynthia S.","family":"Crowson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7335-7321","authenticated-orcid":false,"given":"Tanaz A.","family":"Kermani","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Orla Ni","family":"Mhuircheartaigh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3109-6207","authenticated-orcid":false,"given":"Helene","family":"Alexanderson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"2262","published-online":{"date-parts":[[2020,4,15]]},"reference":[{"key":"2022062114101690000_48.1.94.1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM197502132920706"},{"key":"2022062114101690000_48.1.94.2","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/ken441"},{"key":"2022062114101690000_48.1.94.3","doi-asserted-by":"publisher","DOI":"10.1016\/S0003-9993(00)90212-0"},{"key":"2022062114101690000_48.1.94.4","doi-asserted-by":"publisher","DOI":"10.1002\/art.22996"},{"key":"2022062114101690000_48.1.94.5","doi-asserted-by":"publisher","DOI":"10.1111\/j.1475-097X.2010.00973.x"},{"key":"2022062114101690000_48.1.94.6","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/kel017"},{"key":"2022062114101690000_48.1.94.7","doi-asserted-by":"publisher","DOI":"10.1136\/annrheumdis-2011-200587"},{"key":"2022062114101690000_48.1.94.8","first-page":"603","article-title":"Defining clinical improvement in adult and juvenile myositis","volume":"30","author":"Rider","year":"2003","journal-title":"J Rheumatol"},{"key":"2022062114101690000_48.1.94.9","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1097\/00002281-200311000-00002","article-title":"Physical activity and disablement in the idiopathic inflammatory myopathies","volume":"15","author":"Harris-Love","year":"2003","journal-title":"Curr Opin Rheumatol"},{"key":"2022062114101690000_48.1.94.10","doi-asserted-by":"publisher","DOI":"10.1002\/art.1780230202"},{"key":"2022062114101690000_48.1.94.11","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/40.11.1262"},{"key":"2022062114101690000_48.1.94.12","doi-asserted-by":"crossref","first-page":"4538","DOI":"10.3899\/jrheum.161183","article-title":"Muscle strength and muscle endurance during the first year of treatment of polymyositis and dermatomyositis: a prospective study","volume":"45","author":"Alexanderson","year":"2018","journal-title":"J Rheumatol"},{"key":"2022062114101690000_48.1.94.13","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1002\/acr.22473","article-title":"Reliability of the adult myopathy assessment tool in individuals with myositis","volume":"67","author":"Harris-Love","year":"2015","journal-title":"Arthritis Care Res"},{"key":"2022062114101690000_48.1.94.14","first-page":"1380","article-title":"A functional index in myositis","volume":"23","author":"Josefson","year":"1996","journal-title":"J Rheumatol"},{"key":"2022062114101690000_48.1.94.15","doi-asserted-by":"publisher","DOI":"10.1080\/030097400447679"},{"key":"2022062114101690000_48.1.94.16","doi-asserted-by":"crossref","unstructured":"Everitt BS and Skrondal A. 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