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RA features sporadic \u2018flares\u2019 or inflammatory episodes\u2014mostly occurring outside clinics\u2014where symptoms worsen and plasma C-reactive protein (CRP) becomes elevated. Poor control of inflammation results in higher rates of irreversible joint damage, increased disability, and poorer quality of life. Flares need to be accurately identified and managed. A method comparison study was designed to assess agreement between CRP values obtained by dried blood spot (DBS) versus conventional venepuncture sampling. The ability of a weekly DBS sampling and CRP test regime to detect flare outside the clinic was also assessed. Matched venepuncture and finger lancet DBS samples were collected from n\u2009=\u2009100 RA patients with active disease at baseline and 6\u00a0weeks (NCT02809547). A subset of n\u2009=\u200930 RA patients submitted weekly DBS samples over the study period. Patient demographics, including self-reported flares were recorded. DBS sample CRP measurements were made by enzyme-linked immunosorbent assay, and venepuncture samples by a reference immunoturbometric assay. Data was compared between sample types by Bland\u2013Altman and weighted Deming regression analyses. Flare detection sensitivity and specificity were compared between \u2018minimal\u2019 baseline and 6\u00a0week sample CRP data and the \u2018continuous\u2019 weekly CRP data. Baseline DBS ELISA assay CRP measures yielded a mean positive bias of 2.693\u2009\u00b1\u20098.640 (95% limits of agreement \u2212 14.24 to 19.63%), when compared to reference assay data. Deming regression revealed good agreement between the DBS ELISA method and reference assay data, with baseline data slope of 0.978 and intercept -0.153. The specificity of \u2018continuous\u2019 area under the curve (AUC) CRP data (72.7%) to identify flares, was greater than \u2018minimal\u2019 AUC CRP data (54.5%). This study indicates reasonable agreement between DBS and the reference method, especially at low to mid-range CRP values. Importantly, longitudinal CRP measurement in RA patients helps to clearly identify flare and thus could assist in remote monitoring strategies and may facilitate timely therapeutic intervention.<\/jats:p><jats:p><jats:bold><jats:italic>Trial registration<\/jats:italic><\/jats:bold>: The Remote Arthritis Disease Activity MonitoR (RADAR) study was registered on 22\/06\/2016 at ClinicalTrials.gov Identifier: NCT02809547. <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" ext-link-type=\"uri\" xlink:href=\"https:\/\/clinicaltrials.gov\/ct2\/show\/NCT02809547\">https:\/\/clinicaltrials.gov\/ct2\/show\/NCT02809547<\/jats:ext-link>.<\/jats:p>","DOI":"10.1038\/s41598-020-77826-0","type":"journal-article","created":{"date-parts":[[2020,12,3]],"date-time":"2020-12-03T11:02:35Z","timestamp":1606993355000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Assessment of a dried blood spot C-reactive protein method to identify disease flares in rheumatoid arthritis patients"],"prefix":"10.1038","volume":"10","author":[{"given":"Leon G.","family":"D\u2019Cruz","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kevin G.","family":"McEleney","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chris","family":"Cochrane","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kyle B. 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