A new multiplex molecular assay based on padlock probes and rolling circle amplification for MDR-TB detection in clinical specimens: a prospective diagnostic accuracy study.

BACKGROUND

Patients with multidrug-resistant tuberculosis (MDR-TB) receive treatment that is at least 20% less effective than drug-susceptible cases globally.

OBJECTIVES

The study evaluated the diagnostic accuracy of mfloDx MDR-TB assay (EMPE Diagnostics AB, Solna, Sweden) for simultaneous detection of resistance to isoniazid (INH) and rifampicin (RIF) compared to culture-based drug susceptibility test (DST).

DESIGN

A prospective diagnostic accuracy study.

METHODS

Clinical samples from 287 patients (mean age 45.3 (95% CI 43.3-47.2) years; 50 (17.0%) were female) from TB facilities in Ukraine (n = 82, 28.6%), Moldova (n = 37, 12.9%) and Spain (168, 58.5%) with bacteriologically confirmed TB and persons evaluated for non-tuberculous mycobacteria (NTM) were consecutively tested. The results of the mfloDx MDR-TB assay were compared with culture-based DST.

RESULTS

A total of 186 out of 287 sputum specimens (64.8%) yielded conclusive results that allowed a definitive interpretation of resistance to at least one drug. The mfloDx MDR-TB assay demonstrated sensitivity at 86.9 (95% CI 80.6-91.7) and specificity at 100 (95% CI 79.4-100) correctly differentiating mycobacterium tuberculosis complex from NTM in smear positive sputum samples. Considering only conclusive results in sputum samples, the mfloDx MDR-TB assay simultaneously predicted resistance to INH and RIF in TB patients showing high sensitivity 100 (95% CI 93.0-100) and specificity 98.7 (95% CI 92.8-100) compared to MDR-TB detection by culture-based DST.

CONCLUSION

While approximately one-third of tests yielded inconclusive results, the mfloDx™ MDR-TB assay demonstrated potential as a rapid screening tool for INH and RIF resistance, offering a time advantage over conventional culture-based DST.