Kraut JA, et al. - Researchers validated whether the reference limits of serum total CO₂ concentration [TCO₂] in venous blood at sea level be set at 23–30 mEq/L for initial assessment of acid-base status. For this purpose, they used the University of California at Los Angeles (UCLA’s) Integrated Clinical and Research Data Repository, a database containing information on 4.5 million patients seen at UCLA from 2006 to the present. Based on the findings, the proposal that the reference range of serum [TCO₂] in venous blood at sea level be narrowed to 23–30 mEq/L was proved to be valid. To exclude the presence of clinically important acid-base disorders, evaluation with a venous blood gas might be needed for subjects with serum [TCO₂] outside this range.