Table 7.
Effect of correcting ferritin (FER), soluble transferrin receptor (TfR) and retinol-binding protein (RBP) concentrations on the prevalence of low iron status and low vitamin A status in Senegalese schoolchildren, Cambodian schoolchildren and Cambodian women of reproductive age (WRA)
| Senegalese schoolchildren (n 594) | Cambodian schoolchildren (n 2471) | Cambodian WRA (n 2117) | ||||
|---|---|---|---|---|---|---|
| % | P value† | % | P value† | % | P value† | |
| Low FER‡ | ||||||
| Uncorrected | 20·4 | NA | 1·3 | NA | 7·6 | NA |
| In participants with no inflammation | 22·6 | NA | 1·4 | NA | 8·0 | NA |
| Corrected for three phases of inflammation§ | 21·5 | 0·016 | 1·4 | 0·250 | 7·9 | 0·008 |
| Corrected for three phases of inflammation (Thurnham)║ | 22·9 | 0·000 | 1·8 | 0·000 | 8·0 | 0·002 |
| FER<30 µg/l in children with inflammation | 23·2 | 0·000 | 2·1 | 0·000 | 8·9 | 0·000 |
| High TfR¶ | ||||||
| Uncorrected | 33·3 | NA | 51·4 | NA | 10·1 | NA |
| In participants with no inflammation | 32·6 | NA | 42·2 | NA | 9·5 | NA |
| Corrected for three phases of inflammation†† | 33·2 | 1·000 | 42·9 | 0·000 | 9·7 | 0·021 |
| ID (high TfR and/or low FER)‡,¶ | ||||||
| Uncorrected | 38·7 | NA | 51·6 | NA | 13·5 | NA |
| In participants with no inflammation | 38·5 | NA | 42·5 | NA | 13·2 | NA |
| Corrected for three phases of inflammation§,†† | 37·9 | 0·180 | 44·5 | 0·000 | 13·4 | 0·791 |
| Corrected for three phases of inflammation (Thurnham)║ | 39·1 | 0·500 | 51·6 | 1·000 | 13·8 | 0·016 |
| FER<30 µg/l in children with inflammation | 40·2 | 0·004 | 51·7 | 0·500 | 14·3 | 0·000 |
| BID (low body Fe‡‡) | ||||||
| Uncorrected | 16·7 | NA | 1·7 | NA | 5·1 | NA |
| In participants with no inflammation | 18·6 | NA | 1·7 | NA | 5·3 | NA |
| Corrected for three phases of inflammation§,†† | 17·5 | 0·002 | 1·8 | 0·002 | 5·2 | 0·002 |
| Corrected for three phases of inflammation (Thurnham)║ | 17·7 | 0·000 | 1·9 | 0·000 | 5·3 | 0·000 |
| ID-TFI (high TfR/log FER index§§) | ||||||
| Uncorrected | 23·9 | NA | 7·0 | NA | 7·2 | NA |
| In participants with no inflammation | 25·7 | NA | 6·3 | NA | 7·1 | NA |
| Corrected for three phases of inflammation§,†† | 24·6 | 0·125 | 6·3 | 0·000 | 7·2 | 1·000 |
| Corrected for three phases of inflammation (Thurnham)║ | 24·6 | 0·125 | 7·7 | 0·000 | 7·3 | 0·500 |
| FER<30 µg/l for children with inflammation║║ | 26·9 | 0·000 | 13·2 | 0·000 | 7·9 | 0·000 |
| Vitamin A deficiency¶¶ | ||||||
| Uncorrected | 3·7 | NA | 1·0 | NA | 0·5 | NA |
| In participants with no inflammation | 2·9 | NA | 0·9 | NA | 0·4 | NA |
| Corrected for three phases of inflammation††† | 3·4 | 0·500 | 0·9 | 1·000 | 0·4 | 0·500 |
| Corrected for three phases of inflammation (Thurnham)‡‡‡ | 3·0 | 0·125 | 0·7 | 0·031 | 0·3 | 0·250 |
| Marginal vitamin A status§§§ | ||||||
| Uncorrected | 42·1 | NA | 11·4 | NA | 6·0 | NA |
| In participants with no inflammation | 39·7 | NA | 11·0 | NA | 5·7 | NA |
| Corrected for three phases of inflammation††† | 39·6 | 0·000 | 11·7 | 0·427 | 5·9 | 0·687 |
| Corrected for three phases of inflammation (Thurnham)‡‡‡ | 38·9 | 0·000 | 8·7 | 0·000 | 5·6 | 0·008 |
| Zn deficiency║║║ | ||||||
| Uncorrected | 27·2 | NA | 92·8 | NA | NA | NA |
| In participants with no inflammation | 27·5 | NA | 93·3 | NA | NA | NA |
| Corrected for three phases of inflammation¶¶¶ | 27·3 | 1·0 | 92·8 | 0·5 | NA | NA |
ID, Fe deficiency; BID, body Fe deficiency; ID-TFI, Fe deficiency defined by high TfR/log FER index; NA, not applicable; CF, correction factor.
McNemar’s χ2 test of proportion to compare uncorrected prevalence and corrected prevalence.
FER<15 µg/l for children and WRA, except if notified.
Using CF in Table 3.
Thurnham’s CF for incubation, early convalescence and late convalescence: 0·64, 0·39 and 0·65 in children; 0·73, 0·58 and 0·85 in women.
TfR>8·3 mg/l.
Using CF in Table 4.
Body Fe<0 mg/kg.
TfR/logFER>7·05 (corresponding to 8·3/log15).
TfR/logFER>5·3 (corresponding to 8·3/log30).
RBP<0·7 µmol/l.
Using CF in Table 5.
Thurnham’s CF for incubation, early convalescence and late convalescence: 0·87, 0·76 and 0·89.
RBP<1·05 µmol/l.
Zn<9·9 µmol/l, 10·1 µmol/l or 10·7 µmol/l, respectively, in children aged <10 years, girls aged >10 years and boys aged >10 years.
Using CF in Table 6.