Host iron redistribution as a risk factor for incident tuberculosis in HIV infection: an 11-year retrospective cohort study

Table 2 Host iron as a risk factor for incident tuberculosis in HIV infection

	Model 1: IRR, unadjusted		Model 2: IRR, adjusted for acute phase response		Model 3: IRR, adjusted for known TB risk factors*
	Is the host iron status biomarker a risk factor for incident TB in HIV infection?		Does the biomarker remain an independent risk factor after adjusting for a marker of the host acute phase response (baseline α-₁-antichymotrypsin concentration)?		Does the biomarker remain an independent risk factor for incident TB in HIV infection after adjusting for baseline age, CD4, body mass index?
Iron factors	IRR (95% CI)	P	IRR (95% CI)	P	IRR (95% CI)	P
Transferrin, g/L	0.25 (0.19-0.35)	< 0.001	0.30 (0.21-0.43)	< 0.001	0.53 (0.33-0.84)	0.007
Transferrin saturation, %	1.00 (0.99-1.01)	0.691	1.00 (0.99-1.01)	0.691	1.00 (0.99-1.01)	0.669
Ferritin, μg/L	1.71 (1.49-1.97)	< 0.001	1.60 (1.35-1.89)	< 0.001	1.26 (1.05-1.51)	0.014
Hemoglobin, g/L	0.79 (0.73-0.86)	< 0.001	0.84 (0.77-0.92)	< 0.001	0.88 (0.79-0.98)	0.023
Iron, μmol/L	0.92 (0.88-0.95)	< 0.001	0.94 (0.91-0.97)	< 0.001	0.96 (0.92-1.01)	0.104
Transferrin receptor, nmol/L	1.01 (1.00-1.02)	0.160	1.01 (1.00-1.02)	0.130	1.00 (0.99-1.01)	0.991

Main effects for iron status biomarkers assessed using complete data with multiplicative Poisson regression models with differences estimated on a log scale and expressed as incidence rate ratios (IRR).
Ferritin and absolute CD4 cell counts were natural-logarithm transformed; BMI was dummy-coded as <18.5 or ≥18.5 kg/m²; self-reported ethnicity was dummy-coded as Mandinka, Wolof, Fula, Jola or Otherwise.
*In this dataset, unadjusted Poisson regression analyses indicated sex (females) (IRR, 95% CI = 0.53, 0.38 to 0.73), and higher absolute CD4 (IRR, 95% CI = 0.56, 0.50 to 0.64) were associated with significantly lower risk of incident TB and body mass index < 18.5 (IRR, 95% CI = 2.02, 1.33 to 3.08) was associated with a significantly higher risk of TB. Age (IRR, 95% CI = 1.02, 1.00 to 1.04) was not a direct risk factor for TB in this dataset, but age was included in models as it is commonly associated with differential risk of TB.
CI = 95% confidence interval; IRR = incidence rate ratio; TB = tuberculosis (all forms).

ISSN: 1471-2334