Novel point-of-care TB test for patients with HIV superior to current test
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Study findings showed that a novel point-of-care tuberculosis test for patients with HIV offers superior diagnostic sensitivity to the currently available test while maintaining specificity, researchers reported.
The researchers said the test, the SILVAMP TB LAM (FujiLAM, Fujifilm), could transform rapid point-of-care TB diagnosis for patients with HIV.
“Most tuberculosis-related deaths in people with HIV could be prevented with earlier diagnosis and treatment. The only commercially available tuberculosis point-of-care test — [Alere Determine TB LAM Ag, (AlereLAM, Abbott)] — has suboptimal sensitivity, which restricts its use in clinical practice,” Tobias Broger, MSc, of the Foundation for Innovative New Diagnostics (FIND) in Geneva, and colleagues wrote in The Lancet Infectious Diseases. “The novel FujiLAM assay has been developed to improve the sensitivity of AlereLAM.”
To determine the diagnostic accuracy of the new assay, Broger and colleagues assessed urine samples collected from adult hospital inpatients with HIV during three independent prospective cohort studies in South Africa. According to the study, 968 urine samples were tested between April 18 and May 3, 2018, using both the FujiLAM and AlereLAM assays.
Using the microbiological reference standard, Broger and colleagues estimated the FujiLAM assay to have a higher sensitivity compared with the AlereLAM assay — 70.4% (95%, CI = 53 to 83.1) vs. 42.3% (95%, CI = 31.7 to 51.8). Additionally, they found the estimated specificity of FujiLAM to be 90.8% (95% CI, 86 to 94.4), compared with 95% (95% CI, 87.7 to 98.8) for AlereLAM.
“Considering the substantially improved sensitivity of FujiLAM compared with AlereLAM and the high diagnostic yield compared with sputum-based diagnostics, the FujiLAM assay has the potential to substantially improve rapid diagnosis of tuberculosis in patients with HIV who are admitted to hospital and potentially people with HIV in the general population,” they concluded. “Since AlereLAM has demonstrated survival benefit, FujiLAM might potentially further reduce tuberculosis-related mortality in people with HIV. These findings will inform a WHO policy review for lipoarabinomannan-based diagnostic tests of active tuberculosis.” – by Caitlyn Stulpin
Disclosures: Broger is employed by the Foundation for Innovative New Diagnostics. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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David L. Cohn, MD
This study done by investigators from South Africa, FIND and others showed that the sensitivity of the novel FujiLAM urine assay was greater than that of the currently approved and WHO-recommended AlereLAM test for the diagnosis of TB in selected persons with HIV infection, with similar specificity. Importantly, the sensitivity was better in patients who were the most immunocompromised, ie, those with CD4 cell counts of less than100/µL, the population for whom this test was designed.
Numerous studies have shown that persons with TB (often disseminated) and advanced HIV disease are at high risk for early mortality and may be difficult to diagnose because of severe morbidity, inability to produce sputum, and low sensitivity of sputum tests by smear and culture. In prior studies, the sensitivity of the Alere LAM test resulted in the rapid diagnosis of TB in many of these patients, leading to earlier anti-TB and ART; it was shown to have a modest benefit in preventing mortality in multi-country studies. This study by Broger and colleagues showed the superior accuracy of FujiLAM in a retrospective analysis of specimens saved from three well-characterized cohorts of patients in Cape Town. It remains to be seen if similar performance characteristics will be demonstrated in prospective studies and whether even more lives can be saved with this promising and innovative point-of-care test. Other important considerations will be cost and feasibility to implement this test in different settings in resource-limited countries, ie, tertiary care centers, district hospitals and community centers.
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