Table 1.

Characteristics of the Third National Health and Nutrition Examination Survey populationa

CharacteristicWomen (n = 8506)Men (n = 7465)
a All values are unweighted mean ± SD unless otherwise stated. CrCl, creatinine clearance.
b In 8434 women and 7403 men.
Age (yr)48 ± 2048 ± 20
Weight (kg)70 ± 1880 ± 17
Race/ethnicity (non-Hispanic white/non-Hispanic black/Mexican American/other) (%)42/28/26/441/26/29/4
Hemoglobin (g/dl)13.1 ± 1.214.9 ± 1.3
Hematocrit (%)39 ± 344 ± 4
Serum creatinine (μmol/L) (mg/dl)88 ± 26 (1.0 ± 0.3)106 ± 35 (1.2 ± 0.4)
CrCl (ml/min)83 ± 3388 ± 32
    number (%) of subjects with:
        CrCl > 80 ml/min4206 (49%)4530 (61%)
        80 ≥ CrCl > 70 ml/min1206 (14%)878 (12%)
        70 ≥ CrCl > 60 ml/min961 (11%)670 (9%)
        60 ≥ CrCl > 50 ml/min786 (9%)532 (7%)
        50 ≥ CrCl > 40 ml/min621 (7%)437 (6%)
        40 ≥ CrCl > 30 ml/min462 (5%)298 (4%)
        30 ≥ CrCl > 20 ml/min225 (3%)92 (1%)
        CrCl ≤ 20 ml/min39 (0.5%)28 (0.4%)
Transferrin saturation (%)b (median, interquartile range)23 ± 11 (21, 15–28)28 ± 12 (27, 20–34)
Serum ferritin (ng/ml)b (median, interquartile range)90 ± 122 (54, 26–110)184 ± 166 (141, 83–232)
Erythrocyte protoporphyrin (μg/dl)b (median, interquartile range)59 ± 41 (51, 42–63)47 ± 25 (42, 35–51