{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T08:27:52Z","timestamp":1787128072399,"version":"build-2736575974"},"reference-count":53,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2026,8,9]],"date-time":"2026-08-09T00:00:00Z","timestamp":1786233600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>Background: This study aimed to compare a chemiluminescence immunoassay (CLIA; Siemens Atellica IM 1600) with an automated liquid chromatography\u2013tandem mass spectrometry (LC\u2013MS\/MS) analyser (Thermo Scientific Cascadion SM) for serum 25-hydroxyvitamin D [25(OH)D] measurement in unselected outpatients, and its impact on clinical classification. Methods: 25(OH)D was measured on 1064 paired serum samples (828 women, 236 men; age 3\u2013111 years); both platforms participated in the Vitamin D Standardisation Program (VDSP). Agreement was assessed by the Wilcoxon signed-rank test, Passing\u2013Bablok regression, Bland\u2013Altman analysis on log-transformed values, Breusch\u2013Pagan testing for heteroscedasticity, consistency-based intraclass correlation coefficient (ICC), Lin\u2019s concordance correlation coefficient, and Cohen\u2019s kappa with McNemar\u2019s test on six- and two-category clinical classifications. Results: Methods differed significantly (p&lt;2.2\u00d710\u221216). Passing\u2013Bablok regression showed proportional bias (slope 1.33; 95% confidence interval [CI], 1.28\u20131.38; LC\u2013MS\/MS higher). Consistency ICC was 0.928 (95% CI, 0.919\u20130.936). Log-Bland\u2013Altman bias was 35.5% (limits of agreement, \u221218.3% to +124.5%; heteroscedasticity, p=5.18\u00d710\u221211). Cohen\u2019s kappa was 0.32 unweighted and 0.72 weighted on six clinical categories, and 0.56 on a two-class scheme (McNemar p&lt;2.2\u00d710\u221216). In discordant pairs, CLIA classified deficiency 118-fold more often than LC\u2013MS\/MS. Conclusions: In our study, despite preserved rank ordering, a non-linear concentration-dependent bias and different limits of agreement caused systematic differences in the classification of vitamin D deficiency. Adoption of automated LC\u2013MS\/MS can substantially reclassify outpatients toward sufficiency, with implications for supplementation and laboratory harmonisation.<\/jats:p>","DOI":"10.3390\/diagnostics16162514","type":"journal-article","created":{"date-parts":[[2026,8,10]],"date-time":"2026-08-10T01:20:03Z","timestamp":1786324803000},"page":"2514","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Comparison of LC\u2013MS\/MS and CLIA Methods for Vitamin D Measurement in an Unselected Outpatient Cohort: Statistical Evaluation and Impact on Clinical Classification"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-0872-6249","authenticated-orcid":false,"given":"Carlo","family":"Corbetta","sequence":"first","affiliation":[{"name":"Laboratory Research Unit, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"},{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1218-230X","authenticated-orcid":false,"given":"Luigi","family":"Corsaro","sequence":"additional","affiliation":[{"name":"Medical Genetic Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9729-6722","authenticated-orcid":false,"given":"Eugenio","family":"Caradonna","sequence":"additional","affiliation":[{"name":"Laboratory Research Unit, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chiara","family":"Rusconi","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ivana De","family":"Rosa","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2325-106X","authenticated-orcid":false,"given":"Stefano","family":"Diani","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2583-690X","authenticated-orcid":false,"given":"Veniero","family":"Gambaro","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"},{"name":"Department of Pharmaceutical Science, Universit\u00e0 Degli Studi di Milano, Via Luigi Mangiagalli 25, 20133 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8648-0372","authenticated-orcid":false,"given":"Ugo de","family":"Grazia","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-9950-7673","authenticated-orcid":false,"given":"Alessandro","family":"Maiocchi","sequence":"additional","affiliation":[{"name":"Bracco S.p.A., Via Egidio Folli 50, 20134 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5425-4335","authenticated-orcid":false,"given":"Fulvio","family":"Ferrara","sequence":"additional","affiliation":[{"name":"Integrated Laboratory Medicine Service, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6732-8092","authenticated-orcid":false,"given":"Lucy","family":"Costantino","sequence":"additional","affiliation":[{"name":"Medical Genetic Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katia","family":"Roda","sequence":"additional","affiliation":[{"name":"Clinical Pathology Laboratory, CDI\u2014Centro Diagnostico Italiano S.p.A., Via Saint Bon 20, 20147 Milan, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"491S","DOI":"10.1093\/ajcn\/88.2.491S","article-title":"From vitamin D to hormone D: Fundamentals of the vitamin D endocrine system essential for good health","volume":"88","author":"Norman","year":"2008","journal-title":"Am. 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