JNM: PET may predict drug-resistant tuberculosis in HIV patients

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With the deficiencies in knowledge of tuberculosis—as well as in the practices, programs and strategies used to combat the disease and co-infection with HIV—the spread of multidrug-resistant tuberculosis poses a major problem for the healthcare community. Research in the June issue of the Journal of Nuclear Medicine, however, showed that the use of 18F-FDG PET scans can help to determine earlier if treatment for tuberculosis is working or if the disease is multidrug-resistant.

Tuberculosis and HIV have been linked since the AIDS epidemic began. Approximately 33.2 million people across the world are living with HIV, and an estimated one-third of them are co-infected with tuberculosis. In 2008, the number of multidrug-resistant tuberculosis cases reached between 390,000 and 510,000, or 3.6 percent of all incident tuberculosis cases. Multidrug-resistant tuberculosis is very difficult to treat and is often fatal. 

"Early detection of drug resistance of tuberculosis allows the initiation of an appropriate treatment, which may significantly affect patient survival. Currently, more than two-thirds of patients with multidrug-resistant tuberculosis die," said the study’s lead author Mike Sathekge, MD, PhD, chief specialist of the nuclear medicine department at the Pretoria Academic Hospital in Pretoria, South Africa.

In the prospective pilot study, 24 patients with tuberculosis underwent 18F-FDG PET scans prior to receiving tuberculosis treatment—the standard triad: isoniazid, rifampicin and ethambutol.

After four months of treatment, the study participants received another 18F-FDG scan to measure averaged maximum standardized uptake value (SUVmax)—which measures glucose metabolic activity—derived from early and delayed imaging, percentage change in SUVmax and number of involved lymph node basins.

The researchers found that SUVmax of involved lymph nodes, number of involved lymph node basins and C-reactive protein levels assessed by the PET scan were significantly higher in nonresponders than responders.

Based on the findings of their study, Sathekge and colleagues concluded that a cutoff of five or more involved lymph node basins allowed for separation of tuberculostatic responsive and nonresponsive tuberculosis-infected HIV patients with a sensitivity of 88 percent, a specificity of 81 percent and a negative predictive value of 93 percent.

According to Sathekge, "18F-FDG PET has the 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." 

The authors also noted that the findings warrant confirmation by additional studies on larger cohorts of patients.