{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,25]],"date-time":"2026-07-25T12:06:03Z","timestamp":1784981163750,"version":"3.55.0"},"reference-count":25,"publisher":"Oxford University Press (OUP)","issue":"9","license":[{"start":{"date-parts":[[2023,6,13]],"date-time":"2023-06-13T00:00:00Z","timestamp":1686614400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["asbmr.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["JBMR Plus"],"published-print":{"date-parts":[[2023,9]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>\n                    Vitamin D deficiency is prevalent in 25% of Americans. However, 25(OH)D may not be an accurate measure of vitamin D because the majority (85%\u201390%) of 25(OH)D is bound to vitamin D binding protein (VDBP), which varies by over 30% across individuals. Free 25(OH)D may be a better measure, but it is difficult to measure accurately and precisely. The existing free 25(OH)D estimating equation does not include VDBP phenotypes; therefore, new equations that include this variable may be more accurate. A total of 370 participants in the Health, Aging, and Body Composition Study, a cohort of healthy community\u2010dwelling individuals aged 70\u201379\u2009years old, underwent VDBP and vitamin D metabolite [25(OH)D, 24,25(OH)\n                    <jats:sub>2<\/jats:sub>\n                    D, 1,25(OH)\n                    <jats:sub>2<\/jats:sub>\n                    D, free 25(OH)D] measurements and were randomly allocated into equation development (two out of three) and internal validation (one out of three) groups. New equations were developed with multiple linear regression and were internally validated with Bland\u2013Altman plots. The mean age was 75\u2009\u00b1\u20093\u2009years, 53% were female, and the mean measured free 25(OH)D was 5.37\u2009\u00b1\u20091.81\u2009pg\/mL. Three equations were developed. The first equation included albumin, 25(OH)D\n                    <jats:sub>3<\/jats:sub>\n                    , 25(OH)D\n                    <jats:sub>2<\/jats:sub>\n                    , VDBP, 1,25(OH)\n                    <jats:sub>2<\/jats:sub>\n                    D\n                    <jats:sub>3<\/jats:sub>\n                    , and 24,25(OH)\n                    <jats:sub>2<\/jats:sub>\n                    D\n                    <jats:sub>3<\/jats:sub>\n                    . The second equation included all variables in Eq. (1) plus VDBP phenotypes. The third equation included albumin, 25(OH)D\n                    <jats:sub>3<\/jats:sub>\n                    , intact parathyroid hormone, and 1,25(OH)\n                    <jats:sub>2<\/jats:sub>\n                    D\n                    <jats:sub>3<\/jats:sub>\n                    . In internal validation, all three new equations predicted free 25(OH)D values within 30% and 15% of the measured free 25(OH)D concentrations in 76%\u201380% and 48%\u201352% of study participants, respectively. Equation (2) was the most precise, with a mean bias of 0.06 (95% limits of agreement \u22122.41 to 2.30) pg\/mL. The existing equation estimated free 25(OH)D within 30% and 15% of measured free 25(OH)D in 43% and 22% of participants, respectively. Free 25(OH)D can be estimated with clinically available biomarkers as well as with more laboratory\u2010intensive biomarkers with moderate precision. \u00a9 2023 The Authors.\n                    <jats:italic>JBMR Plus<\/jats:italic>\n                    published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.\n                  <\/jats:p>","DOI":"10.1002\/jbm4.10781","type":"journal-article","created":{"date-parts":[[2023,6,13]],"date-time":"2023-06-13T04:55:55Z","timestamp":1686632155000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Development and Validation of Novel Free Vitamin D Equations: The Health Aging and Body Composition Study"],"prefix":"10.1093","volume":"7","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7278-3409","authenticated-orcid":false,"given":"Jonathan H.","family":"Cheng","sequence":"first","affiliation":[{"name":"Division of Nephrology\u2010Hypertension University of California  San Diego CA USA"},{"name":"Nephrology Section Veterans Affairs San Diego Healthcare System  San Diego CA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6449-0243","authenticated-orcid":false,"given":"Andrew N.","family":"Hoofnagle","sequence":"additional","affiliation":[{"name":"Department of Laboratory Medicine and Medicine and the Kidney Research Institute University of Washington  Seattle WA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ronit","family":"Katz","sequence":"additional","affiliation":[{"name":"Department of Obstetrics and Gynecology University of Washington  Seattle WA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stephen B.","family":"Kritchevsky","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine, Section on Gerontology and Geriatric Medicine Wake Forest School of Medicine  Winston\u2010Salem NC USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael G.","family":"Shlipak","sequence":"additional","affiliation":[{"name":"Kidney Health Research Collaborative, Veterans Affairs Medical Center University of California  San Francisco CA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark J.","family":"Sarnak","sequence":"additional","affiliation":[{"name":"Department of Medicine, Division of Nephrology Tufts Medical Center  Boston MA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joachim H.","family":"Ix","sequence":"additional","affiliation":[{"name":"Division of Nephrology\u2010Hypertension University of California  San Diego CA USA"},{"name":"Nephrology Section Veterans Affairs San Diego Healthcare System  San Diego CA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Charles","family":"Ginsberg","sequence":"additional","affiliation":[{"name":"Division of Nephrology\u2010Hypertension University of California  San Diego CA USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2023,6,13]]},"reference":[{"key":"e_1_2_10_2_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.amjmed.2003.12.029"},{"key":"e_1_2_10_3_1","doi-asserted-by":"publisher","DOI":"10.14336\/AD.2016.1021"},{"key":"e_1_2_10_4_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41430-020-0558-y"},{"key":"e_1_2_10_5_1","unstructured":"NIH.Office of Dietary Supplements\u2010Vitamin D [Internet];2021. Available from:https:\/\/ods.od.nih.gov\/factsheets\/VitaminD-HealthProfessional\/."},{"key":"e_1_2_10_6_1","doi-asserted-by":"publisher","DOI":"10.1530\/EC-18-0432"},{"key":"e_1_2_10_7_1","doi-asserted-by":"publisher","DOI":"10.1053\/j.ajkd.2018.03.026"},{"key":"e_1_2_10_8_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.bone.2017.11.011"},{"key":"e_1_2_10_9_1","doi-asserted-by":"publisher","DOI":"10.1002\/jbmr.387"},{"key":"e_1_2_10_10_1","article-title":"Vitamin D and DBP: the free hormone hypothesis revisited","volume":"144","author":"Chun RF","year":"2014","journal-title":"J Steroid Biochem Mol Biol"},{"key":"e_1_2_10_11_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMc1502602"},{"key":"e_1_2_10_12_1","doi-asserted-by":"publisher","DOI":"10.1093\/clinchem\/hvaa238"},{"key":"e_1_2_10_13_1","doi-asserted-by":"publisher","DOI":"10.1093\/aje\/kwx297"},{"key":"e_1_2_10_14_1","doi-asserted-by":"publisher","DOI":"10.1172\/JCI111617"},{"key":"e_1_2_10_15_1","doi-asserted-by":"publisher","DOI":"10.1210\/jcem.84.10.6079"},{"key":"e_1_2_10_16_1","doi-asserted-by":"publisher","DOI":"10.1210\/jcem-63-4-954"},{"key":"e_1_2_10_17_1","doi-asserted-by":"publisher","DOI":"10.1210\/jc.2013-3874"},{"issue":"1","key":"e_1_2_10_18_1","first-page":"205","article-title":"Vitamin D status of black and white Americans and changes in vitamin D metabolites after varied doses of vitamin D supplementation. The American journal of clinical nutrition","volume":"104","author":"Alzaman NS","year":"2016","journal-title":"American Society for Nutrition"},{"issue":"17","key":"e_1_2_10_19_1","first-page":"1695","article-title":"Group for the OF in M (MrOS) R. Role of assay type in determining free 25\u2010hydroxyvitamin D levels in diverse populations. The New England journal of medicine","volume":"374","author":"Nielson CM","year":"2016","journal-title":"NIH Public Access"},{"key":"e_1_2_10_20_1","doi-asserted-by":"publisher","DOI":"10.3389\/fendo.2019.00317"},{"key":"e_1_2_10_21_1","unstructured":"Health ABC.Introducing the health ABC study: The dynamics of health aging and body composition;2021. Available from:https:\/\/healthabc.nia.nih.gov\/."},{"key":"e_1_2_10_22_1","doi-asserted-by":"publisher","DOI":"10.1373\/clinchem.2015.244541"},{"key":"e_1_2_10_23_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa1114248"},{"key":"e_1_2_10_24_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ecl.2017.07.013"},{"key":"e_1_2_10_25_1","doi-asserted-by":"publisher","DOI":"10.1007\/BF00219689"},{"key":"e_1_2_10_26_1","doi-asserted-by":"publisher","DOI":"10.1007\/BF00194311"}],"container-title":["JBMR Plus"],"original-title":[],"language":"en","deposited":{"date-parts":[[2024,3,14]],"date-time":"2024-03-14T09:58:14Z","timestamp":1710410294000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/jbmrplus\/article\/7\/9\/n\/a\/7612282"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,13]]},"references-count":25,"journal-issue":{"issue":"9","published-print":{"date-parts":[[2023,9]]}},"alternative-id":["10.1002\/jbm4.10781"],"URL":"https:\/\/doi.org\/10.1002\/jbm4.10781","archive":["Portico"],"relation":{"has-review":[{"id-type":"doi","id":"10.1002\/JBM4.10781\/v2\/response1","asserted-by":"object"},{"id-type":"doi","id":"10.1002\/JBM4.10781\/v1\/decision1","asserted-by":"object"},{"id-type":"doi","id":"10.1002\/JBM4.10781\/v2\/review1","asserted-by":"object"},{"id-type":"doi","id":"10.1002\/JBM4.10781\/v1\/review1","asserted-by":"object"},{"id-type":"doi","id":"10.1002\/JBM4.10781\/v2\/decision1","asserted-by":"object"},{"id-type":"doi","id":"10.1002\/JBM4.10781\/v1\/review2","asserted-by":"object"}]},"ISSN":["2473-4039","2473-4039"],"issn-type":[{"value":"2473-4039","type":"print"},{"value":"2473-4039","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,6,13]]},"assertion":[{"value":"2023-01-25","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-05-22","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2023-06-13","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e10781"}}