The WHO recommends that each patient with suspected tuberculosis should benefit from at least one NAAT (nucleic acid amplification test), as these tests have enhanced sensitivity and specificity above conventional microscopy. Over the past years, the Xpert® MTB/RIF test has been used as the test of choice, replacing staining techniques such as ZN or Auramine on the first respiratory specimen submitted for each patient.
The Xpert MTB/RIF Ultra assay (Ultra) now replaces the Xpert® MTB/RIF as the next–generation assay. It has a higher sensitivity than Xpert MTB/RIF for the detection of Mycobacterium tuberculosis, particularly in smear-negative culture-positive specimens and in testing specimens from HIV-infected patients and children. It is also superior in testing extra pulmonary specimens such as CSF. The Ultra is also better able to differentiate silent mutations from rifampicin resistance conferring mutations (i.e. less false-resistant results than with the Xpert® MTB/RIF assay).
Xpert® MTB/RIF Ultra assay