This article is more than 5 years old. Information may no longer be current.
Xpert MTB/RIF assay cleared to determine if TB patients need isolation
Click Here to Manage Email Alerts
The FDA has cleared the Cepheid Xpert MTB/RIF Assay for determining if patients with suspected tuberculosis can be removed from airborne isolation.
One or two negative test results on the assay will help health care providers decide if patients with signs and symptoms of TB should be kept in isolation. The CDC recommends that patients suspected of having TB be kept in isolation until clinical and laboratory tests, which include three acid-fast bacilli (AFB) smear tests on three sputum specimens collected 8 to 24 hours apart, demonstrate the patient is unlikely to have TB.
“The revised labeling states that the results from one or two consecutive negative tests using MTB/RIF will strongly predict the results that would be obtained from AFB smear testing of three sputum specimens for the TB bacteria,” Alberto Gutierrez, PhD, director of the office of in vitro diagnostics and radiological health at the FDA’s Center for Devices and Radiological Health, said in a press release. “This information, along with other patient clinical data, can be valuable in deciding whether a patient can spread TB to other people and whether continued airborne isolation is necessary.”
Alberto Gutierrez
The FDA’s updated indication was based on clinical data that demonstrated one or two consecutive negative results from the MTB/RIF test correctly identified patients who would test negative for TB bacteria by AFB smear testing. One negative test predicted a negative AFB smear test 99.7% of the time. Two negative tests predicted the absence of the bacteria 100% of the time.
The decision to use one or two MTB/RIF tests will be based on individual patients and on hospital guidelines.
“We are encouraged that a quicker option for detecting contagious TB is now available to assist in determining whether patients must remain in isolation,” Philip LoBue, MD, director of the CDC’s Division of Tuberculosis Elimination, said in the release. “The test may make it possible for some patients to be released from hospital isolation sooner, freeing up limited medical resources and removing restrictions on patients’ movements and interactions. While this test can assist health care providers in making important decisions regarding isolation, it does not replace the continued need for culture testing to ensure patients with TB are accurately diagnosed and treated.”
The CDC said the MTB/RIF test may not detect all patients with active TB; thus health care workers must continue to follow the CDC’s current guidelines, and collect consecutive sputum specimens for TB culture testing even if the MTB/RIF results are negative. Approximately 10% to 15% of patients with active TB cannot be detected with the test, requiring culture for correct diagnosis. Although these patients will not usually require isolation, culture is necessary to ensure the patients receive TB treatment.