A-045 Serum Magnesium Levels: A Comparative Study of Reference Values

Background Magnesium is an essential electrolyte for metabolic and physiological functions. Its deficiency affects 3–10% of the global population, often asymptomatically, leading to underdiagnosis, particularly among the elderly. Studies from the 1980s suggested adjusting reference values. Currently, serum analysis devices define specific ranges based on reagent package inserts. However, ISO 15189:2012 recommends adapting reference values to the population. Thus, updating reference values is essential to better reflect health conditions and reduce underdiagnosis. Methods A total of 144,822 serum magnesium measurements from a Brazilian outpatient population (2022–2024) were analyzed to determine reference values based on the median and interquartile range using DataR. The prevalence of magnesium disorders was evaluated using three cutoff points: Group 1 (1.3–2.7 mg/dL, per the Advia 1800-Siemens reagent insert); Group 2 (1.7–2.4 mg/dL, per Clinical Chemistry and Laboratory Medicine [2023] and NEJM [2024]); and Group 3 (1.6–2.4 mg/dL, based on the studied population). The analysis considered sex, age, and self-reported magnesium supplementation. Descriptive analyses were conducted, and data were evaluated using the Wilcoxon rank-sum test, chi-square test, and Fisher’s exact test, with statistical significance set at p < 0.001. Results A total of 144,823 magnesium measurements were analyzed, with 35.88% from males (n = 51,976) and 64.11% from females (n = 92,847). The cohort included 8,750 individuals under 18 years old, 71,323 aged 18–60, and 61,750 over 60 years old. Among females, mean serum magnesium levels were 2.04 mg/dL (<18 years), 2.00 mg/dL (18–60 years), and 2.00 mg/dL (>60 years). Among males, mean serum magnesium levels were 2.07 mg/dL (<18 years), 2.03 mg/dL (18–60 years), and 1.99 mg/dL (>60 years). Only 0.52% of participants reported magnesium supplementation (608 females and 137 males), with increased use among those over 60 years old (55.60% of supplemented females, 67.88% of supplemented males). When analyzed with different cutoffs, hypomagnesemia prevalence was 0.2% (n = 340) in Group 1, lower than expected in the literature, with 81.17% of cases (n = 277) occurring in individuals over 60 years old. In Group 2, the prevalence was 4.3% (n = 6,198), consistent with literature expectations, with 67.76% (n = 4,193) of cases in those over 60. In Group 3, based on the local population (1.6–2.4 mg/dL), prevalence was 2.1% (n = 3,105), with 73.07% (n = 2,269) of cases occurring in individuals over 60 years old. Conclusion Reference values in reagent package inserts may not adequately reflect serum magnesium variations. Modifying the package insert cutoff to literature-based values quadruples hypomagnesemia prevalence, while local population-based values double it. This adjustment may significantly reduce underdiagnosis, particularly among the elderly. Laboratories should define reference intervals tailored to their populations. More appropriate values can enhance early detection and intervention. Additionally, large-scale studies using big data and international comparisons are essential. A multicenter study is necessary to establish more precise and widely applicable reference values.