Abstract
BackgroundThe understanding of early events following TB exposure is limited by traditional tests that rely on detection of an immune response to infection, which is delayed, or on imaging tests with low sensitivity for early disease. We investigated for evidence of lung abnormalities in heavily exposed TB contacts using PET/MRI.Methods30 household contacts of 20 index patients underwent clinical assessment, IGRA testing, chest x-ray and PET/MRI scan using 18-F-FDG. MRI images were examined by a radiology/nuclear medicine dual-qualified physician using a standardised report form, while PET/MRI images were examined independently by another radiology/nuclear medicine dual-qualified physician using a similar form. Standardised uptake value (SUV) was quantified for each abnormal lesion.ResultsIGRA was positive in 40%. PET/MRI scan was abnormal in 30%, predominantly FDG uptake in hilar or mediastinal lymph nodes and lung apices. We did not identify any relationship between PET/MRI findings and degree of exposure or IGRA status.ConclusionPET-based imaging may provide important insights into the natural history following exposure to TB that may not be available from traditional tests of TB immune response or imaging. The clinical significance of the abnormalities is uncertain and merits further investigation in longitudinal studies.
Highlights
The understanding of early events following TB exposure is limited by traditional tests that rely on detection of an immune response to infection, which is delayed, or on imaging tests with low sensitivity for early disease
No contact reported a history of Human immunodeficiency virus (HIV) or diabetes mellitus
Using the new approach of Positron emission tomography (PET)/Magnetic resonance imaging (MRI), we identified increased metabolic activity in lymph nodes or lung parenchyma in approximately one third of heavily-exposed household TB contacts
Summary
The understanding of early events following TB exposure is limited by traditional tests that rely on detection of an immune response to infection, which is delayed, or on imaging tests with low sensitivity for early disease. Studies using Computed Tomography (CT) imaging have identified changes consistent with active TB in just under a third of TST or IGRA positive TB contacts [3,4,5,6,7]. In a study of HIV infected patients with latent TB, PET/CT identified abnormalities consistent with subclinical TB in just under a third of cases [8]. Another small PET/CT study identified lymph node activity in four of five asymptomatic IGRA-positive TB contacts [9]. The aim of our study was to investigate a much larger group of contacts using PET magnetic resonance imaging (PET/MRI) to look for early abnormalities
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