Our study showed that the incidence of AF was 22.5% in a heterogeneous group of septic shock patients and that Δmax249 ≤ 9 μg/dl may be a better option for AF diagnosis whenever free cortisol measurement is not available, since Δmax249 ≤ 9 μg/dl was not affected by serum albumin while the baseline total cortisol levels and their cutoff values varied directly according to albumin levels. The gene discussed is ALB; the disease is atrial fibrillation.