Individuality of the plasma sodium concentration.
Older literature has suggested that the plasma sodium concentration is not individual, that it is neither intrinsic to an individual nor reproducible, longitudinally. We recently observed that the plasma sodium concentration is heritable. Because demonstrable heritability requires individuality of the relevant phenotype, we hypothesized that the plasma sodium concentration was substantially individual. In two large health plan-based cohorts, we demonstrated individuality of the plasma sodium concentration over a 10-yr interval; the intraclass correlation coefficient (ICC) averaged 0.4-0.5. The individuality of plasma sodium increased significantly with age. Plasma sodium individuality was equal to or only slightly less than that for plasma glucose but was less than the individuality for creatinine. The individuality of plasma sodium was further confirmed by comparing the Pearson correlation coefficient for within-individual versus between-individual pairs of sodium determinations and via application of the agreement index. Furthermore, the distribution of all sodium determinations for all participants within a population was similar to the distribution for the mean sodium concentration for individuals within that population. Therefore, the near-normal distribution of plasma sodium measurements within a population is likely not attributable to assay-specific factors but rather to genuine and durable biological variability in the osmotic set point. In aggregate, these data strongly support the individuality of the plasma sodium concentration. They further indicate that serial plasma sodium values for any given individual tend to cluster around a patient-specific set point and that these set points vary among individuals.
Department of Biostatistics, Brown University School of Medicine, Providence, Rhode Island;
Zheng
Z
Zhang
Health Service Research and Development, Portland Veterans Affairs Medical Center, Portland, Oregon.
Jonathan
J
Duckart
Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health and Science University, Portland, Oregon; Section of Pulmonary and Critical Care Medicine, Portland Veterans Affairs Medical Center, Portland, Oregon; and.
Christopher G
CG
Slatore
Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon; Oregon Health and Science University, Portland, Oregon; Section of Nephrology, Portland Veterans Affairs Medical Center, Portland, Oregon;
Yi
Y
Fu
The Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon; and.
Amanda F
AF
Petrik
The Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon; and.
Micah L
ML
Thorp
Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon; Oregon Health and Science University, Portland, Oregon; Section of Nephrology, Portland Veterans Affairs Medical Center, Portland, Oregon; cohend@ohsu.edu.
David M
DM
Cohen
D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood*; D001786:Blood Glucose / Q000378:metabolism; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D007206:Individuality; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012964:Sodium / Q000097:blood*
D001786:Blood Glucose; D012964:Sodium; D003404:Creatinine
human; hyponatremia; osmoregulation; population