The effect of inflammation on serum zinc concentrations and the prevalence estimates of population-level zinc status among Congolese children aged 6-59 months

BACKGROUND/OBJECTIVES: Zinc is a negative acute-phase reactant; hence, its concentration decreases in the presence of inflammation. There is no current consensus on how to control for the effect of inflammation on serum zinc, which has implications for accurate estimates of population-level zinc status. We aimed to measure the association between inflammation and serum zinc concentrations and to compare the means and the prevalence of zinc deficiency using unadjusted and inflammation-adjusted serum zinc concentrations among Congolese children. SUBJECTS/METHODS: Non-fasting blood was collected in the afternoon in trace element-free vacutainers from 744 apparently healthy children aged 6-59 months in the Democratic Republic of the Congo. Serum was analyzed for zinc, C-reactive protein (CRP) and alpha-1 acid glycoprotein (AGP) for 665 children with complete data for all three biomarkers. Linear regression was used to generate correction factors (CFs) based on three stages of inflammation: incubation (CRP 45 mg/l and normal AGP), early convalescence (CRP > 5 mg/l and AGP > 1 g/l) and late convalescence (AGP > 1 g/l and normal CRP), relative to no inflammation. RESULTS: Overall unadjusted mean +/- s.d. serum zinc concentration was 9.4 +/- 2.1 mu mol/l. Study-generated CFs (95% confidence interval) for incubation, early and late convalescence were 1.01 (0.88, 1.14), 1.15 (1.11, 1.21) and 1.07 (1.03, 1.11), respectively. After applying the CFs, overall adjusted mean +/- s.d. serum zinc concentration was 10.1 +/- 2.2 mu mol/l, and prevalence of zinc deficiency (<8.7 mu mol/l) decreased from 35% (n = 234/665) to 24% (n = 160/665). CONCLUSIONS: Adjustment of zinc concentrations for inflammation is warranted when assessing population-level zinc status.