TABLE 3.
Summary of vitamin A biomarkers reflective of deficiency or elevated status among PSC, SAC, nonpregnant WRA, and men in the 2015–2016 MNS1
| Biomarker and cutoffs for vitamin A status | RBP <0.46 µmol/L2 | Serum retinol <0.7 µmol/L3,4 | MRDR ratio3 | Fasted serum retinyl esters >5% (children) or 7.5% (women)3,5 | Fasted serum retinyl esters >10% | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| n | % (95% CI) | n | % (95% CI) | n | mean ± SE | n | % (95% CI) | n | % (95% CI) | |
| PSC (6–59 mo) | 1102 | 3.6 (1.7, 5.4) | 171 | 1.8 (0.0, 4.6) | 73 | 0.018 ± 0.001 | 73 | 18.0 (6.4, 29.6) | 73 | 1.7 (0.0, 4.1) |
| SAC (5–14 y) | 758 | 0.9 (0.1, 1.7) | 178 | 4.4 (0.0, 9.7) | 80 | 0.011 ± 0.001 | 80 | 18.8 (7.2, 30.5) | 80 | 4.9 (0.0, 10.2) |
| Nonpregnant WRA (15–49 y) | 752 | 0.3 (0.0, 0.8) | 181 | 1.9 (0.0, 4.4) | 94 | 0.010 ± 0.001 | 94 | 1.3 (0.0, 2.9) | 94 | 0.9 (0.0, 2.3) |
| Men | 219 | 0.1 (0.0, 0.3) | NA | NA | NA | NA | NA | NA | NA | NA |
RBP and MRDR results adapted with permission from the 2015–2016 Malawi micronutrient survey report (19). Serum retinol results adapted with permission from the Malawi Micronutrient Survey 2015–2016 Addendum: Additional Vitamin A Biomarker Results, February 2020 (35). MDHS, Malawi Demographic and Health Survey; MNS, Malawi National Micronutrient Survey; MRDR, modified relative dose response; NA, not applicable; PSC, preschool age children; RBP, retinol binding protein; SAC, school age children; WRA, women of reproductive age.
RBP equivalent to 0.7 µmol retinol/L was calculated using linear regression to estimate a survey-specific retinol binding protein cutoff to reflect vitamin A deficiency. Retinol binding protein concentrations for women and children were not adjusted for inflammation in the 2015–2016 Malawi micronutrient survey report, although guidance suggests that child concentrations be adjusted. The decision not to adjust for inflammation was based on the prevalence of deficiency being very low. There were 5 PSC [weighted estimate of 0.4 (0.0–0.9)] and no SAC with inflammation adjusted RBP <0.46 µmol/L.
The serum retinol (fasting and nonfasting), MRDR (fasting only), and serum retinyl esters (fasting only) were collected from a random subsample designed to be representative at the national level.
The 2015–2016 serum retinol was inflammation-adjusted using the BRINDA regression method for children but was not inflammation-adjusted for women (24). No other biomarkers in the table were adjusted for inflammation.