Day-to-day variation in iron-status indices in healthy men and women.
We evaluated the day-to-day variation of four iron-status indices: hemoglobin (Hb), hematocrit (Hct), plasma ferritin (PF), and plasma iron (PI). Finger-prick blood samples were collected for 31 consecutive days in 20 healthy men and women. Replicate (sigma 2rep) and day-to-day (sigma 2day) variance components were estimated. Day-to-day variation in the iron-status measures was similar between men and women except for PF, for which the variation was greater in women. The CVs for a single future determination for Hb, Hct, PF, and PI were 4.6%, 3.0%, 15.2%, and 26.7% for males and 4.4%, 3.2%, 26.8%, and 29.0% for females, respectively. Three to 10 independent measurements are required to accurately determine PF and PI whereas one is adequate for Hb and Hct. Thus, day-to-day biological variation is a major component of the variability in these iron-status indicators and must be considered when assessing iron status.
Borel
M J
MJ
Department of Nutrition, Pennsylvania State University, University Park 16802.
Smith
S M
SM
Derr
J
J
Beard
J L
JL
D000328:Adult; D000704:Analysis of Variance; D015331:Cohort Studies; D005260:Female; D005293:Ferritins / Q000032:analysis*; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007501:Iron / Q000097:blood*; D008297:Male; D011336:Probability; D012016:Reference Values; D012727:Sex Characteristics
D006454:Hemoglobins; D005293:Ferritins; D007501:Iron