A new 60-minute on-site lateral flow assay showed the same sensitivity as mycobacterial culture in detecting tuberculosis meningitis (TBM) in adult HIV patients, according to a clinical infectious disease study.
The main risk factors for TBM include young age and HIV infection. The aim of this prospective study was to evaluate the Fujifilm SILVAMP TB LAM Assay (FujiLAM), a point-of-care lateral flow assay that requires 0.2 ml of sample, and its ability to detect the presence of TBM in adults to identify. The FujiLAM was originally developed to test urine. In this study, however, the researchers tested cerebrospinal fluid (CSF) for mycobacterial lipoarabinomannan. Most of the study participants had HIV.
In the study, the FujiLAM showed a sensitivity of 79 percent, the same sensitivity as the mycobacterial culture compared to a microbiological reference standard that includes culture and ultra. The sensitivity of FujiLAM was 52 percent compared to a reference standard for microbiologically confirmed plus clinically probable TBM. This level of sensitivity was almost as high as Ultra’s 55 percent sensitivity.
The study researchers found that FujiLAM was more likely to be positive in patients with high CSF bacterial loads, as well as in those with advanced HIV infection and increased mortality. In contrast, they suggested that FujiLAM cannot be used as an exclusion test, as the FujiLAM failed to detect approximately 26 percent of cases with microbiologically confirmed TBM.
The specificity of TBM was reportedly “excellent” for the detection of TBM. For this reason, the researchers suggested that the likelihood that a patient in this population would have TBM increased from 57 to 97 percent if the FujiLAM test was positive. Only 1 false positive FujiLAM test was found using a reference standard of microbiologically confirmed plus clinically probable TBM.
One limitation of this study included the inability to perform reference and index tests on all samples and the insufficient volume of CSF tested, resulting in inconsistent use of reference and index tests on CSF samples.
The study’s researchers concluded that “for the first time ever, a true rapid-of-care test shows promise for diagnosing this bedside infection”. They added that if the “clinical benefits of FujiLAM can be demonstrated, the global health community should ensure the commercial availability of FujiLAM at an affordable cost.”
Broger T, Nicol MP. A novel bedside rule-in test for tuberculous meningitis in HIV-infected adults. Published online January 6, 2021. Clin Infect Dis. doi: 10.1093 / cid / ciaa1915