Stratified Reference Intervals for Serum Selenium by Selenium Environment, Health, and Physiological Status in Populations from Shaanxi Province, China.

Serum selenium (Se) is a core indicator for evaluating human selenium nutritional status. In Shaanxi Province, considerable geographical variation in selenium environment distribution limits the applicability of generalized reference intervals, which do not account for regional or physiological differences. This study aimed to establish stratified serum/hair Se reference intervals for populations with different physiological statuses across high-Se, adequate-Se, and low-Se regions in Shaanxi Province, China, and to identify key influencing factors, thereby providing region-specific evidence for selenium monitoring and intervention. This study integrated multiple datasets from Shaanxi Province, China, including pregnant women, healthy adults, hospitalized patients, and children aged 7-12 years, and comprised two components: (1) a multicenter observational analysis to establish stratified serum and hair selenium reference intervals and evaluate environmental factors, and (2) a selenium supplementation intervention in children from a low-selenium region to assess changes in hair selenium after supplementation. Multiple sets of stratified reference intervals were established: 32.7-96.5 µg/L for healthy adults (adequate-Se), 30.1-86.7 µg/L for healthy women, 32.8-89.7 µg/L for pregnant women (high-Se), 33.1-68.2 µg/L for pregnant women (medium-to-high Se composite), 35.2-88.2 µg/L for elderly hospitalized patients (adequate-Se), and 0.2-0.5 µg/g for hair Se in supplemented children (low-Se). Region, age, and liver/kidney function were identified as core influencing factors. Hair Se levels in children from low-Se regions were significantly increased after Se supplementation. This study established stratified Se reference intervals for populations with different Se environments and health/physiological statuses in Shaanxi Province, China, providing region-specific evidence for selenium assessment and for cautiously tailored nutritional intervention in comparable settings.