Correlation Between CT Features of Active Tuberculosis and Residual Metabolic Activity on End-of-Treatment FDG PET/CT in Patients Treated for Pulmonary Tuberculosis

Ismaheel O Lawal; Kgomotso M G Mokoala; Matsontso Mathebula; Ingrid Moagi; Gbenga O Popoola; Nontando Moeketsi; Maphoshane Nchabeleng; Chris Hikuam; Jerrold J Ellner; Mark Hatherill; Bernard P Fourie; Mike M Sathekge

doi:10.3389/fmed.2022.791653

Correlation Between CT Features of Active Tuberculosis and Residual Metabolic Activity on End-of-Treatment FDG PET/CT in Patients Treated for Pulmonary Tuberculosis

Front Med (Lausanne). 2022 Feb 22:9:791653. doi: 10.3389/fmed.2022.791653. eCollection 2022.

Authors

Affiliations

¹ Department of Nuclear Medicine, University of Pretoria, Pretoria, South Africa.
² Nuclear Medicine Research Infrastructure, Steve Biko Academic Hospital, Pretoria, South Africa.
³ Department of Medical Microbiology and MeCRU, Sefako Makgatho University of Medical Science, Pretoria, South Africa.
⁴ Department of Epidemiology and Community Health, University of Ilorin, Ilorin, Nigeria.
⁵ South African Tuberculosis Vaccine Initiative, Department of Pathology, Institute of Infectious Disease and Division of Immunology, University of Cape Town, Cape Town, South Africa.
⁶ Department of Medicine, Centre for Emerging Pathogens, Rutgers-New Jersey Medical School, Newark, NJ, United States.
⁷ Department of Medical Microbiology, University of Pretoria, Pretoria, South Africa.

Abstract

Patients who complete a standard course of anti-tuberculous treatment (ATT) for pulmonary tuberculosis and are declared cured according to the current standard of care commonly have residual metabolic activity (RMA) in their lungs on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PER/CT) imaging. RMA seen in this setting has been shown to be associated with relapse of tuberculosis. The routine clinical use of FDG PET/CT imaging for treatment response assessment in tuberculosis is hindered by cost and availability. CT is a more readily available imaging modality. We sought to determine the association between CT features suggestive of active tuberculosis and RMA on FDG PET/CT obtained in patients who completed a standard course of ATT for pulmonary tuberculosis. We prospectively recruited patients who completed a standard course of ATT and declared cured based on negative sputum culture. All patients had FDG PET/CT within 2 weeks of completing ATT. We determined the presence of RMA on FDG PET images. Among the various lung changes seen on CT, we considered the presence of lung nodule, consolidation, micronodules in tree-in-bud pattern, FDG-avid chest nodes, and pleural effusion as suggestive of active tuberculosis. We determine the association between the presence of RMA on FDG PET and the CT features of active tuberculosis. We include 75 patients with a mean age of 36.09 ± 10.49 years. Forty-one patients (54.67%) had RMA on their FDG PET/CT while 34 patients (45.33%) achieved complete metabolic response to ATT. There was a significant association between four of the five CT features of active disease, p < 0.05 in all cases. Pleural effusion (seen in two patients) was the only CT feature of active disease without a significant association with the presence of RMA. This suggests that CT may be used in lieu of FDG PET/CT for treatment response assessment of pulmonary tuberculosis.

Keywords: FDG PET/CT; HIV infection; computed tomography; end-of-treatment; pulmonary tuberculosis; residual metabolic activity.