Evaluating Truenat Assay for the Diagnosis of Ocular Tuberculosis and Detection of Drug Resistance.

ABSTRACT

BACKGROUND: Truenat MTB Plus assay was evaluated for diagnosing ocular tuberculosis (OTB) and detecting multi-drug resistant (MDR) and extremely-drug resistant (XDR) OTB. METHODS: A total of 75 vitreous fluid specimens [five confirmed OTB, 40 clinically suspected OTB and 30 controls] were subjected to Truenat MTB Plus, multiplex PCR, and Xpert Ultra. Chips of Truenat were used for detecting rifampicin, isoniazid, fluoroquinolone and bedaquiline resistance. The performance was compared against culture, composite reference standard, and gene sequencing. RESULTS: The overall sensitivity of TruePlus, MPCR, and Ultra in diagnosing OTB was 66.6%, 73.3%, and 55.5%, respectively. Out of six cases with mutations in rpoB gene, RifR was detected in five by TrueRif and four by Ultra. Three MDR and one XDR-OTB were reported by Truenat. CONCLUSION: Truenat assay along with its strategic chips is a rapid and reliable tool for diagnosis of OTB and detection of drug resistance, including MDR and XDR-OTB.Abbreviations OTB Ocular tuberculosis; XDR Extremely drug resistant; Ultra Xpert MTB/RIF Ultra; Xpert Xpert MTB/RIF; PCR polymerase chain reaction; NAATs Nucleic acid amplification tests; MDR Multi Drug Resistant; NSP National Strategic plan for elimination of tuberculosis; FqR Fluoroquinolone resistant; BdqR bedaquiline resistant; TrueRif Truenat MTB Rif Dx; TruePlus Truenat Plus; INH Isoniazid; DST Drug susceptibility testing; MGIT Mycobacterial growth indicator tube; CRF Composite reference standard; PPV positive predictive value; NPV negative predictive value; EPTB extrapulmonary tuberculosis; VF vitreous fluid; DNA deoxyribonucleic acid; ATT antitubercular therapy; RifR Rifampicin resistance; RifS Rifampicin susceptible; RifI Rifampicin indeterminate.