{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T03:44:37Z","timestamp":1782704677016,"version":"3.54.5"},"reference-count":34,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T00:00:00Z","timestamp":1782432000000},"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: Serum 25-hydroxyvitamin D [25(OH)D] interpretation requires clear distinction between epidemiological thresholds, routine-data distributions, and clinical decision limits. This study evaluated vitamin D status and clinically pre-filtered routine laboratory data-derived 25(OH)D distributional benchmarks among adults from \u015eanl\u0131urfa, southeastern T\u00fcrkiye, according to sex, age, and season. Methods: This retrospective single-center routine laboratory database study included adults aged 18\u201365 years tested between 1 January and 31 December 2025, at the Medical Biochemistry Laboratory of \u015eanl\u0131urfa Mehmet Akif \u0130nan Training and Research Hospital. After eligibility screening, duplicate removal, analytical screening, and predefined clinical pre-filtering, 48,826 participant-level records were analyzed. Serum 25(OH)D was measured using the Elecsys Vitamin D total III electrochemiluminescence immunoassay on a cobas e 801 analyzer\/module. The primary distributional estimate was the nonparametric 2.5th\u201397.5th percentile range. Results: Median age was 38 [28\u201349] years, and 35,043 records were from female participants (71.8%). Median serum 25(OH)D was 12.74 [8.28\u201319.00] ng\/mL. Vitamin D deficiency, severe deficiency, insufficiency, and sufficiency were observed in 38,072 (78.0%), 17,163 (35.2%), 8235 (16.9%), and 2519 (5.2%) records, respectively. Lower 25(OH)D concentrations and higher deficiency prevalence were observed among females, younger adults, and winter\/spring samples, with small-to-modest effect magnitudes. The clinically pre-filtered routine-data 2.5th\u201397.5th percentile range was 3.46\u201335.50 ng\/mL. Conclusions: Low 25(OH)D status was widespread among routinely tested adults in \u015eanl\u0131urfa. The derived range should be interpreted only as a local routine-data distributional benchmark for the tested population, not as a healthy-volunteer reference interval, clinical sufficiency threshold, treatment threshold, or clinical decision limit.<\/jats:p>","DOI":"10.3390\/diagnostics16131995","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T02:16:44Z","timestamp":1782699404000},"page":"1995","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Vitamin D Status and Routine Laboratory Data-Derived 25(OH)D Distributional Benchmarks in Adults from \u015eanl\u0131urfa, T\u00fcrkiye: Age, Sex, and Seasonal Variation"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0459-0629","authenticated-orcid":false,"given":"Mehmet Akif","family":"Bozdayi","sequence":"first","affiliation":[{"name":"Department of Medical Biochemistry, Mehmet Akif Inan Education and Research Hospital, 63300 Sanliurfa, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G\u00f6khan","family":"\u00c7ak\u0131rca","sequence":"additional","affiliation":[{"name":"Department of Medical Biochemistry, Mehmet Akif Inan Education and Research Hospital, 63300 Sanliurfa, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u0130smet Gamze","family":"Bozdayi","sequence":"additional","affiliation":[{"name":"Department of Medical Biochemistry, Sanliurfa Education and Research Hospital, 63200 Sanliurfa, T\u00fcrkiye"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1109","DOI":"10.1210\/er.2018-00126","article-title":"Skeletal and extraskeletal actions of vitamin D: Current evidence and outstanding questions","volume":"40","author":"Bouillon","year":"2019","journal-title":"Endocr. 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