Which statement best describes the purpose of rifampin resistance detection by rapid molecular testing?

• A. It signals potential MDR-TB
• B. It confirms drug-susceptible TB
• C. It indicates ethambutol resistance
• D. It has no significance

Answer: (A)

The main concept being tested is that rifampin resistance detected by rapid molecular testing is used as a fast signal for potential MDR-TB. Tests such as Xpert MTB/RIF quickly identify mutations in the rpoB gene, which confer rifampin resistance. Because rifampin resistance is highly associated with resistance to isoniazid—the defining feature of multidrug-resistant TB—this rapid result lets clinicians start appropriate MDR-TB treatment and implement infection control while full drug-susceptibility testing is still pending. It does not confirm drug-susceptible TB, and it specifically targets rifampin resistance rather than ethambutol resistance. The rapid detection has important clinical and public health implications by reducing delays in initiating effective therapy and reducing transmission.