NTP-Philippines Implements XPERT MTB/XDR for Rapid
Detection of Fluoroquinolone Resistance
(Photo credit: Ilocos Training and Regional Medical Center TB Laboratory c/o Ms Rhoda Cervas)
The World Health Organization (WHO) has recommended the Xpert MTB/XDR Assay (by Cepheid) as a follow-on test for the detection of fluoroquinolone (Fq)-resistance among patients with MDR/RR-TB. It provides results in less than 90 minutes, faster than the currently used line probe assay (LPA) and culture-based drug susceptibility testing. It has a sensitivity for Fq resistance detection of 93% and specificity of 98%, thereby allowing a rapid and accurate detection of Fq resistance. The assay is the first low complexity automated NAAT (nucleic acid amplification test) that also detects resistance to isoniazid, ethionamide, and amikacin.
The National Tuberculosis Control Program (NTP) has issued Department Memorandum 2021-0501 “Use of the Xpert MTB/XDR Assay for the Rapid Detection of Drug-resistant Tuberculosis (DR-TB)” (Link here) stipulating the operational and technical guidelines in the implementation of Xpert MTB/XDR in the country. In October 2021, WHO-country office donated 5 units of the 10-color Xpert machines strategically designated in TB reference laboratories, namely 1) National TB Reference Laboratory (NTRL) 2) Ilocos Training and Regional Medical Center (ITRMC) 3) Western Visayas Medical Center (WVMC) 4) Zamboanga City Medical Center and 5) Davao TB Reference Laboratory.
After internal validation by the National TB Reference Laboratory, the test now allows access to RR-TB patients for the identification of Fq-resistant cases who are the primary candidates for enrollment into the BPaL Operational Research (OR). The table below shows the zoning scheme of catchment regions and BPaL OR sites to the Xpert MTB/XDR laboratory. The Department Memo provides a guide for specimen handling and decision-making based on test results.
Table 1. Specimen referral and health facility zoning mechanism scheme for Xpert MTB/XDR
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