New Point-of-Care TB Test Has High Sensitivity in HIV+ Patients

By Anne Harding

June 19, 2019

NEW YORK (Reuters Health) - A new point-of-care (POC) assay is more sensitive for diagnosing tuberculosis in hospitalized patients with HIV than the only commercially available POC TB test, with comparable specificity, according to new findings.

"Considering the higher sensitivity and rapid, point-of-care design of FujiLAM, this assay has the potential to transform the diagnosis of tuberculosis in hospital inpatients with HIV and, potentially, for people with HIV in the general population," Dr. Claudia M. Denkinger of FIND, in Geneva, and colleagues write in The Lancet Infectious Diseases, online May 30.

TB is the top infectious-disease killer globally, and the leading cause of death in people with HIV, Dr. Denkinger and her team write. The World Health Organization has named non-sputum-based tests for TB as an "urgent unmet clinical need," they add.

The older Alere Determine TB LAM Ag assay (AlereLAM from Abbott), which detects liporabinomannan (LAM) in urine, has 45% sensitivity in HIV patients overall, although it is more sensitive in people with HIV and CD4 counts of 100 cells/uL of blood or less, the authors note.

While its sensitivity is low, the test does reduce mortality among inpatients with HIV, so WHO recommends it for immunocompromised and seriously ill HIV patients, the team notes.

The new test, Fujifilm SILVAMP TB LAM (FujiLAM from Fujifilm), detects LAM in urine on an instrument-free platform in less than an hour. The authors compared the diagnostic accuracy of AlereLAM and FujiLAM in urine samples from 968 hospitalized HIV patients. The patients had a median CD4 count of 86 cells/uL, and 62% had microbiologically confirmed TB.

Based on the microbiological reference standard, the researchers estimated sensitivity of FujiLAM at 70.4%, versus 42.3% for AlereLAM, while specificity were 90.8% and 95.0%, respectively.

Using the composite reference standard, specificities were higher, at 95.7% for FujiLAM and 98.2% for AlereLAM, while sensitivities were lower, at 64.9% vs. 38.2%, respectively.

"Collectively, these results suggest that, if implemented in clinical practice and linked with appropriate treatment, the FujiLAM point-of-care assay might be able to save lives by enabling earlier diagnosis of HIV-associated tuberculosis in a large proportion of hospital inpatients," Dr. Denkinger and her team write.

"The applicability of FujiLAM for settings of intended use requires prospective assessment," they conclude.

"The development of a second simple, rapid, point-of-care test is a major step forward for advancing tuberculosis diagnostics and could save lives as a result of early detection and treatment," Dr. Paul K. Drain of the University of Washington in Seattle and colleagues write in an accompanying editorial.

"However," they add, "as has been observed with the AlereLAM assay, WHO endorsement and inclusion on the Essential Diagnostics List might not necessarily lead to rapid uptake. For lives to be saved by the use of these point-of-care tests, implementation and modelling studies are needed to provide more guidance for national tuberculosis programs."

SOURCE: https://bit.ly/2wO5QLJ and https://bit.ly/2XFljcJ

Lancet Infect Dis 2019.

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