Table 3.
Factors associated with ZPP (μmol/mol haem) measured in erythrocytes a
| Univariate analysis | Multivariate analysis b | |||||
|---|---|---|---|---|---|---|
| Δ c | (95% CI) | P | Δ c | (95% CI) | P | |
| Gravidity | 0.13 | |||||
| Primigravida | [Reference] | – | ||||
| Secundigravida | 23.4% | (–4.3% to 59.2%) | – | |||
| Multigravida | 23.2% | (0.0% to 51.7%) | – | |||
| Gestational age | 0.48 | |||||
| 13–14 weeks | [Reference] | – | ||||
| 15–16 weeks | –4.6% | (–29.4% to 29.0%) | – | |||
| 16–18 weeks | 13.9% | (–15.3% to 53.2%) | – | |||
| 19–21 weeks | 6.1% | (–21.6% to 43.8%) | – | |||
| 22–25 weeks | –5.0% | (–33.1% to 34.8%) | – | |||
| Anaemia | 94.6% | (–67.5% to 126.2%) | <0.001 | 46.3% | (26.9% to 68.8%) | <0.001 |
| Iron deficiencyd | 87.6% | (–62.1% to 117.1%) | <0.001 | 41.0% | (21.5% to 63.5%) | <0.001 |
| Plasma sTfR concentration, mg/L | 48.3% | (–40.0% to 57.1%) | <0.001 | 34.2% | (25.6% to 43.3%) | <0.001 |
| Plasma transferrin concentration, g/L | 85.3% | (–63.2% to 110.4%) | <0.001 | 15.6% | (0.9% to 32.5%) | 0.04 |
| Plasma folate concentration, μg/L | 0.6% | (–1.8% to 2.9%) | 0.64 | 24.0% | (3.0% to 49.3%) | 0.02 |
| Plasma vitamin B12 concentration, 100pmol/L | –3.5% | (–6.4% to –0.7%) | 0.02 | – | ||
| Plasma total bilirubin concentration, μmol/L | –3.0% | (–4.8% to –1.1%) | 0.002 | –2.2% | (–3.7% to –0.7%) | 0.005 |
| Plasma LDH concentration, 10 IU/L | –0.4% | (–1.2% to 0.3%) | 0.21 | –0.1% | (–0.2% to 0.0%) | 0.003 |
| α +-thalassaemia genotype | 0.87 | |||||
| Normal | [Reference] | – | ||||
| Heterozygote | –5.9% | (–25.2% to 18.3%) | – | |||
| Homozygote | –4.7% | (–37.9% to 46.2%) | – | |||
| Plasmodium infection | ||||||
| Any Plasmodium spp., by any dipstick or PCR | –3.0% | (–17.5% to 14.1%) | 0.71 | – | ||
| Current or recent P. falciparum infectione | –10.2% | (–26.3% to 9.5%) | 0.29 | – | ||
| P. falciparum, by dipstick,e or PCR | –3.0% | (–17.5% to 14.1%) | 0.71 | – | ||
| P. falciparum, by PCR | –1.4% | (–16.3% to 16.3%) | 0.87 | – | ||
| HIV infection | –8.5% | (–24.6% to 11.0%) | 0.37 | – | ||
| Plasma CRP concentration, mg/L | –0.1% | (–0.6% to 0.5%) | 0.82 | – | ||
| Plasma AGP concentration, g/L | 1.4% | (–24.0% to 35.2%) | 0.92 | – | ||
| Inflammationf | ||||||
| Plasma CRP concentration ≥10 mg/L | –2.1% | (–18.0% to 16.8%) | 0.81 | – | ||
| Plasma AGP concentration ≥1.0 g/L | 3.2% | (–15.8% to 26.5%) | 0.76 | – | ||
| Plasma CRP concentration ≥10 mg/L, or AGP ≥1.0 g/L | –4.2% | (–19.0% to 13.2%) | 0.61 | – | ||
AGP, α 1-acid glycoprotein; CRP, C-reactive protein; sTfR, Soluble transferrin receptor; ZPP, Zinc protoporphyrin.
aZPP values were normalised by log transformation; exponentiation of results yielded associations being expressed as percentage differences; bThe table shows only results for factors that were independently associated with whole blood ZPP and erythrocyte ZPP; because these final (parsimonious) models were obtained with backward elimination procedures, this resulted in different sets of factors being included for whole blood ZPP and erythrocyte ZPP; cDifference; dPlasma ferritin concentration <15 μg/L; eEither HRP2- or pLDH-based dipstick; fPlasma concentrations of CRP >10 mg/L and/or AGP >1 g/L.