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Table 2 Factors associated with ZPP (μmol/mol haem) measured in whole blood a

From: Diagnostic utility of zinc protoporphyrin to detect iron deficiency in Kenyan pregnant women

  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   
  1. AGP, α 1-acid glycoprotein; CRP, C-reactive protein; sTfR, Soluble transferrin receptor; ZPP, Zinc protoporphyrin.
  2. 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.