Biological variation of hematology tests based on the 1999-2002 National Health and Nutrition Examination Survey.

OBJECTIVE: Biological variation consists of between-person (BP) and within-person (WP) variation. Estimates of WP coefficients of variation (CVw) and BP coefficients of variation (CVg) for hematology laboratory tests were estimated from the 1999-2002 National Health and Nutrition Examination Survey (NHANES).
METHODS: NHANES is a survey of the civilian noninstitutionalized U.S. population that uses a stratified, multistage probability design. Between- and within-person variations were estimated for 18 hematology tests. For WP variation, a nonrandom sample was obtained with a median of 17 days between two test measurements. Between-person variation was estimated from the WP sample and additional participants were matched for age group, gender, and race and ethnicity to the WP sample.
RESULTS: The BP and WP variations were estimated on as many as 2496 and 852 sample participants, respectively. Mean corpuscular hemoglobin concentration had the lowest CVg (2.25% for men and 2.40% for women), and mean corpuscular volume had the lowest CVw (0.31% for men and 0.37% for women). The index of individuality (CVw/CVg) ranged from 0.06 for mean corpuscular volume for men and women to 0.62 for segmented neutrophil number for men, and 0.55 for segmented neutrophil percent for women. Women had higher CVw compared with men for hematocrit, hemoglobin, mean corpuscular volume, red blood cell count, and red blood cell distribution width. Several hematology tests' CVw also differed by age group, including mean corpuscular volume; eosinophil, lymphocyte and segmented neutrophil percent; monocyte and segmented neutrophil number; white blood cell count; and red blood cell distribution width.