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Table 3 Factors associated with ZPP (μmol/mol haem) measured in erythrocytes 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    0.13    
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   
  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.