Possibility of Venous Serum Cl(−) Concentration ([Cl(−)](s)) as a Marker for Human Metabolic Status: Correlation of [Cl(−)](s) to Age, Fasting Blood Sugar (FBS), and Glycated Hemoglobin (HbA1c)

The HCO(3)(−) concentration in venous serum ([HCO(3)(−)](s)) is a factor commonly used for detecting the body pH and metabolic conditions. To exactly detect [HCO(3)(−)](s), the venous CO(2) pressure should be kept as it is in the vein. The [HCO(3)(−)](s) measurement is technically complicated to apply for huge numbers of almost heathy persons taking only basic medical examinations. The summation of [HCO(3)(−)](s) and the venous serum Cl(−) concentration ([Cl(−)](s)) is approximately constant; therefore, we studied if [Cl(−)](s) could be a marker detecting metabolic conditions instead of [HCO(3)(−)](s). Venous blood was obtained from persons taking basic medical examinations (the number of persons = 107,630). Older persons showed higher values of [Cl(−)](s), fasting blood sugar (FBS), and glycated hemoglobin (HbA1c) than younger ones. [Cl(−)](s) showed positive correlation to age and negative correlation to FBS and HBA1c. The negative correlation of [Cl(−)](s) to FBS/HbA1c was obvious in persons with high FBS/HbA1c, leading us to an idea that persons with high FBS/HbA1c show high [HCO(3)(−)](s), which might be caused by low activity of carbonic anhydrase in the lung observed in persons with diabetes mellitus under acidotic conditions. Taken together, an easily measured serum electrolyte, [Cl(−)](s), could be a useful marker estimating metabolic conditions.