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Influence of the matrix type over the concentration of GDF-15

Growth differentiation factor 15 (GDF-15) has been suggested as a prognostic biomarker for bleeding and mortality in atrial fibrillation (AF). To date, serum and EDTA matrices are standardized for the GDF-15 assay but it is unclear if it can be measured also in citrate. In this study, we aim to investigate if the Elecsys GDF-15 assay (Roche Diagnostics, Mannheim, Germany) can be determined accurately in citrate samples in a cohort of 10 patients with AF and 10 healthy controls. From January 2018 to March 2018, we included healthy controls and patients with AF under vitamin K antagonists in a tertiary hospital. Blood samples were drawn in both groups. We included 10 controls (50% males, mean age 36.4±8.9 years) and 10 patients with AF (80% males, mean age 76.5±16.6 years). The mean GDF-15 levels were increased in patients with AF in comparison to healthy controls, as expected by the presence of a heart-related condition and the higher age of this population. In healthy controls, GDF-15 levels showed an optimal correlation between EDTA-serum (r=0.975; p<0.001), EDTA-citrate (r=0.972; p<0.001), and serum-citrate (r=0.997; p<0.001) samples. This was also observed in patients with AF: EDTA-serum (r=0.975; p<0.001), serum-citrate (r=0.835; p=0.003), and EDTA-citrate (r=0.768; p=0.009). Our results demonstrate that citrate samples may be used for the determination of GDF-15 in AF given the positive and good correlation with EDTA and serum matrices. Further studies should validate these observations.