PET scans may help identify multi-drug resistant tuberculosis
MedWire News: A specific type of positron emission tomography (PET) scan can predict whether HIV patients have tuberculosis that is resistant to traditional drug treatment, a study suggests.
The degree of lymph node involvement determined using 18F-FDG PET whole-body scans enabled researchers to distinguish responders to a classic triad of tuberculosis treatment from nonresponders.
The researchers say the scans have the potential to become a valuable clinical adjunct to the available genotypic and phenotypic tests, when the latter are not possible, inconclusive, or too lengthy to be of clinical relevance.
At least 150,000 deaths occur as a result of multidrug resistant tuberculosis each year, say Mike Sathekge (University of Pretoria, South Africa) and colleagues.
In a prospective pilot study, they assessed the relationship between the severity and extent of tuberculosis assessed by 18F-FDG PET at the time of diagnosis and response to treatment after 4 months in 24 HIV patients with newly diagnosed tuberculosis.
Seventeen patients had pulmonary tuberculosis, and seven had extrapulmonary tuberculosis, the authors report in the Journal of Nuclear Medicine.
Participants underwent whole-body 18F-FDG PET before being given tuberculosis treatment using the classic triad of isoniazid, rifampicin, and ethambutol and then received another scan 4 months later.
The average 18F-FDG maximum standardized uptake (SUVmax) of involved lymph node bastions derived from early and late imaging, which measures glucose metabolic activity, was significantly higher in nonresponders than responders to tuberculosis treatment.
The number of involved lymph node bastions and C-reactive protein levels were also significantly higher in nonresponders than responders.
Using a cut off of five or more involved lymph node bastions, responders could be separated from nonresponders with a sensitivity, specificity, and positive and negative predictive value of 88%, 81%, 70%, and 93%, respectively.
A cut off of 8.15 for early SUVmax of lymph node bastions and of 10 for late SUVmax of lymph node bastions showed comparable sensitivity of 88%, but this came at the cost of a lower specificity of 73% and 67%, respectively.
The researchers conclude: "Our findings suggest that 18F-FDG PET may indirectly assess multi-drug resistant status in tuberculosis patients and that 18F-FDG PET has potential to become a valuable clinical adjunct to the already available genotypic and phenotypic tests in patients for whom such tests are not feasible, are inconclusive, or are too lengthy to be of clinical relevance."
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By Anita Wilkinson