Establishing sex- and age-related reference intervals of serum glial fibrillary acid protein measured by the fully automated lumipulse system.

Objectives: To establish the reference intervals (RIs) of serum glial fibrillary acid protein (GFAP) measured by the fully automated Lumipulse system.
Methods: The study population consisted of 340 healthy individuals, including 251 blood donors and 89 outpatients, with a median age of 56 years. Serum GFAP levels were measured by the Lumipulse G GFAP assay on the fully automated platform Lumipulse G1200 (FUJIREBIO Inc., Tokyo, Japan). GFAP RIs (2.5th and 97.5th percentiles) were calculated for the overall population and stratified by age and sex groups. For the overall population, males, and females partitions, we employed the nonparametric methods, while for the age-and-sex groups we employed the "robust" method, as recommended by CLSI.
Results: The RI in the whole population was 10.4-92.0 pg/mL. When considering sex differences, females showed higher levels of serum GFAP than males across all age groups. A positive correlation was observed between age and GFAP (Spearman's rho=0.55, p<0.001). Specifically, the biomarker was stable until 60 years, while individuals aged>60 years demonstrated significantly and considerably higher levels than younger age groups. Additionally, in the 50-60 age group, we observed gender-related differences, with females having increased levels than males.
Conclusions: GFAP levels are influenced by both age and sex. Accordingly, we established RIs of serum GFAP, taking into consideration age and sex-related differences.
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