[18F]FDG PET and CT findings at therapy completion of pulmonary tuberculosis: comparison between HIV-positive and HIV-negative patients and impact on treatment response assessment
Authors: Ismaila Aisha , Lawal Ismaheel O. , Popoola Gbenga O. , Mathebula Matsontso , Moagi Ingrid , Mokoala Kgomotso , Honest Ndlovu , Moeketsi Nontando , Nchabeleng Maphoshane , Hikuam Chris , Hatherill Mark , Fourie P. Bernard , Sathekge Mike Machaba 
Published: May 2024

Abstract
Background
[18F]FDG-PET/CT is a sensitive non-invasive tool for assessing treatment response in patients with pulmonary tuberculosis. The data on the performance of [18F]FDG-PET/CT for response assessment among patients infected with the human immunodeficiency virus (HIV) is limited. Here, we investigated the differences between PET and CT lung findings on end-of-treatment [18F]FDG-PET/CT among HIV-positive versus HIV-negative patients who completed anti-tuberculous therapy for pulmonary tuberculosis.

Methods
Patients who completed anti-tuberculous therapy for pulmonary tuberculosis and declared cured based on negative clinical and laboratory assessments for active pulmonary tuberculosis were prospectively recruited to undergo [18F]FDG-PET/CT. Patients were classified as having residual metabolic activity if PET metabolic activity was demonstrated in the lung parenchyma or complete metabolic response if there was no abnormally increased [18F]FDG avidity in the lungs and compared the CT features. We identified 10 CT lung changes, five were associated with active pulmonary tuberculosis (nodules, micronodules in tree-in-bud pattern, consolidation, pleural effusion, and [18F]FDG-avid mediastinal/hilar lymphadenopathy) and the rest were associated with inactive sequelae of prior pulmonary tuberculosis (cysts, cavities, fibrosis, bronchiectasis, and calcifications and compared their incidence between HIV-positive and HIV-negative patients.

Results
Seventy-five patients were included with a mean age of 36.09 ± 10.49 years. There were fifty HIV-positive patients, all of whom were on antiretroviral therapy and with a median CD4 + T-cell of 255 cells/µL (IQR: 147–488). Fifteen HIV-positive patients had detectable HIV viremia with a median viral load of 12,497 copies/mL (IQR: 158–38,841). There was a significant difference in the incidence of residual metabolic activity and complete metabolic response between HIV-positive and HIV-negative patients. (P = 0.003) HIV-positive patients were more likely to have [18F]FDG-avid lymphadenopathy and HIV-negative patients had a higher incidence of cystic lung changes. The pattern of CT lung changes was otherwise not different between HIV-positive and HIV-negative patients. (P > 0.05)

Conclusions
The incidence of residual metabolic activity and complete metabolic response on end-of-treatment [18F]F-FDG-PET/CT are similar between HIV-positive and HIV-negative patients. The incidence of [18F]FDG-avid mediastinal/hilar lymphadenopathy is more prevalent among HIV-positive patients. The pattern of lung changes was largely similar between HIV-positive and HIV-negative patients, indicating that the presence of HIV coinfection may not influence the interpretation of end-of-treatment [18F]F-FDG-PET/CT obtained for pulmonary tuberculosis treatment response assessment.