Table 2.
Factors associated with ZPP (μmol/mol haem) measured in whole blood a
| Univariate analysis | Multivariate analysis b | |||||
|---|---|---|---|---|---|---|
| Δ c | (95% CI) | P | Δ c | (95% CI) | P | |
| Gravidity | 0.68 | 0.04 | ||||
| Primigravida | [Reference] | [Reference] | ||||
| Secundigravida | –2.3% | (–15.6% to 13.1%) | 0.5% | (–9.6% to 11.8%) | ||
| Multigravida | 2.7% | (–8.9% to 15.7%) | 9.4% | (0.1% to 19.6%) | ||
| Gestational age | 0.87 | 0.008 | ||||
| 13–14 weeks | [Reference] | [Reference] | ||||
| 15–16 weeks | 5.4% | (–11.3% to 25.3%) | 6.7% | (–5.6% to 20.7%) | ||
| 16–18 weeks | 6.1% | (–10.4% to 25.7%) | –4.0% | (–14.9% to 8.3%) | ||
| 19–21 weeks | 2.0% | (–14.3% to 21.3%) | –7.3% | (–18.2% to 5.1%) | ||
| 22–25 weeks | –1.0% | (–19.0% to 20.9%) | –11.0% | (–23.0% to –2.8%) | ||
| Anaemia | 64% | (51.2% to 77.8%) | <0.001 | 33.5% | (23.9% to 43.9%) | <0.001 |
| Iron deficiencyd | 26.3% | (15.8% to 37.8%) | <0.001 | 16.6% | (9.1% to 24.6%) | <0.001 |
| Plasma sTfR concentration, mg/L | 31.9% | (28.1% to 35.9%) | <0.001 | 24.5% | (20.6% to 28.5%) | <0.001 |
| Plasma transferrin concentration, g/L | 30.9% | (21.4% to 41.2%) | <0.001 | – | ||
| Plasma folate concentration, 10 μg/L | 6.1% | (–7.2% to 21.4%) | 0.39 | 12.8% | (2.9% to 22.7%) | 0.01 |
| Plasma vitamin B12 concentration, 100 pmol/L | –1.8% | (–3.4% to –0.2%) | 0.03 | – | ||
| Plasma total bilirubin concentration, μmol/L | 0.7% | (–0.4% to 1.8%) | 0.20 | – | ||
| Plasma LDH concentration, 10 IU/L | 1.5% | (0.6% to 2.5%) | 0.001 | – | ||
| α +-thalassaemia genotype | 0.67 | |||||
| Normal | [Reference] | – | ||||
| Heterozygote | –3.8% | (–16.1% to 10.2%) | – | |||
| Homozygote | –10.0% | (–30.2% to 16.1%) | – | |||
| Plasmodium infection | ||||||
| Any Plasmodium spp., by any dipstick or PCR | 8.0% | (–1.6% to 18.4%) | 0.10 | – | ||
| Current or recent P. falciparum infectione | 5.1% | (–6.2% to 17.8%) | 0.39 | – | ||
| P. falciparum, by dipsticke or PCR | 8.1% | (–1.4% to 18.6%) | 0.10 | – | ||
| P. falciparum, by PCR | 9.9% | (0.1% to 20.7%) | 0.05 | – | ||
| HIV infection | 5.2% | (–14.9% to 6.2%) | 0.37 | – | ||
| Plasma CRP concentration, mg/L | 0.2% | (–0.1% to 0.5%) | 0.27 | – | ||
| Plasma AGP concentration, g/L | 21.5% | (3.2% to 43.0%) | 0.02 | – | ||
| Inflammationf | ||||||
| Plasma CRP concentration ≥10 mg/L | 5.0% | (–5.1% to 16.1%) | 0.34 | – | ||
| Plasma AGP concentration ≥1.0 g/L | 14.0% | (–1.5% to 27.9%) | 0.03 | – | ||
| Plasma CRP concentration ≥10 mg/L, or AGP ≥1.0 g/L | 6.6% | (–3.1% to 17.2%) | 0.19 | – | ||
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.