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Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc
TABLE 14-1 Illustration of the Full Probability Approach to Estimate the Prevalence of Dietary Iron Inadequacy in a Group of 1,000 Menstruating Women (Not Using Oral Contraceptives and Following an Omnivorous Diet)
Percentiles of Requirement Distribution
Range of Usual Intake Associated with Requirement Percentiles (mg/d)
Risk of Inadequate Intake
Number of Women with Intake in Range
Number of Women with Inadequate Intake
< 2.5
< 4.42
1.0
1
1
2.5–5.0
4.42–4.88
0.96
1
0.96
5–10
4.89–5.45
0.93
3
2.79
10–20
5.46–6.22
0.85
10
8.5
20–30
6.23–6.87
0.75
15
11.25
30–40
6.88–7.46
0.65
20
13
40–50
7.47–8.07
0.55
23
12.65
50–60
8.08–8.76
0.45
27
12.15
60–70
8.77–9.63
0.35
50
17.5
70–80
9.64–10.82
0.25
150
37.5
80–90
10.83–13.05
0.15
200
30.0
90–95
13.06–15.49
0.08
175
14
95–97.5
15.50–18.23
0.04
125
5
> 97.5
> 18.23
0.0
200
0
Total
1,000
165
mg/day to 5.45 mg/day, or between the fifth and tenth percentiles) there were three women, with an associated number of women with inadequate intake of 2.79 (3 × 0.93). If this is done for each intake range, the total number of women with inadequate intakes can be determined. In this example, 165 of the 1,000 women have inadequate intakes, for an estimated prevalence of inadequacy of 16.5 percent. It is important to remember that this approach does not identify the specific women with inadequate intakes, but is rather a statistical calculation of the prevalence of inadequate intakes. Thus, it cannot be used to screen individuals at risk of inadequacy.
Note that the prevalence of nutrient inadequacy that is estimated by the full probability approach differs considerably from that estimated by the cut-point method (the proportion with intakes below the EAR). In this example, the EAR (median requirement) is 8.07 mg/day, and only 73 women have intakes below this amount. Thus,
