cobas® MTB-RIF/INH

Rapid resistance testing for proper therapy

Tuberculosis is a bacterial infection caused by species of the Mycobacterium tuberculosis (TB, MTB) complex. A drug resistant strain is defined as resistance to at least one primary drug used to treat tuberculosis. A multidrug resistant TB (MDR-TB) is defined as resistance to at least isoniazid and rifampicin, the two most effective anti-TB drugs, and an extensively drug resistant TB (XDR-TB) is defined as a MDR-TB strain with additional resistance to any fluoroquinolone and at least one injectable second-line TB drug (e.g., amikacin, kanamycin, or capreomycin). In 2017, it was estimated that >5% of incident new TB cases in the world had MDR/RR-TB. The frequency of MDR-TB varies according to region and is higher among previously treated patients.

 

 

cobas® MTB-RIF/INH for use on the cobas® 6800/8800 Systems is an automated, qualitative real-time PCR test designed as a reflex test together with cobas® MTB to detect Rifampicin-resistance associated mutations of the rpoB gene and Isoniazid-resistance associated mutations in the katG and inhA genes, of M. tuberculosis. The test is intended for use on either acid-fast bacilli (AFB) smear-positive or smear-negative, raw sputum, and digested and decontaminated (N-acetyl-L-cysteine/ NaOH treated) sputum and bronchial alveolar lavage (BAL) samples, that tested positive for M. tuberculosis complex by cobas® MTB. Detection of wild-type MTB complex DNA serves as Internal Control to monitor the entire sample preparation and PCR amplification process. In addition, the test utilizes a low titer positive and a negative control.

MTB-RIF-INH-one-third
Molecular Diagnostic Algorithm

Enabling a complete diagnosis is critical to ensure proper therapy is initiated. When patient presents with symptoms of tuberculosis, the cobas® MTB test is performed. If positive, patient should be evaluated for drug resistance using cobas® MTB-RIF/INH test. If negative, the cobas® MAI test can be used to detect a nontuberculosis infection.

Molecular Diagnostics Algorithm
Intended Use

cobas® MTB-RIF/INH for use on the cobas® 6800/8800 Systems is an automated, qualitative in vitro diagnostic test, that utilizes real-time polymerase chain reaction (PCR), for the direct detection of rifampicin-resistance associated mutations of the rpoB gene, and isoniazid-resistance associated mutations in the katG and inhA genes, of Mycobacterium tuberculosis, from human respiratory specimens. The test is intended for use on either acid-fast bacilli (AFB) smear-positive or smear-negative, raw sputum, and digested and decontaminated (N-acetyl-L-cysteine/ NaOH treated) sputum and bronchoalveolar lavage (BAL) samples, that tested positive for Mycobacterium tuberculosis complex (MTBC) by cobas® MTB. This test is intended for use in conjunction with culture and drug susceptibility testing, and as a reflex test together with cobas® MTB, as an aid in the diagnosis of infection with a multidrug resistant M. tuberculosis (MDR-TB).

Ordering Information

 Material Number

 Product Name

 Tests Per Unit

 07833326190

 cobas® MTB-RIF/INH

 72 test cassette

 07833342190

 cobas® MTB-RIF/INH Positive Control Kit

 16 controls x 1mL each

 07002238190

 cobas® 6800/8800 Buffer Negative Control Kit

 16 controls x 1mL each

 08185476001

 cobas® Microbial Inactivation Solution

 16 bottles x 30mL each

Registration Status

CE-IVD, not approved in the US

Package inserts

Access package inserts through your country’s Roche Diagnostics Website.

References

 

  1. Global tuberculosis report 2018. Geneva: World Health Organization; 2018. Licence: CC BY-NC-SA 3.0 IGO.

Specifications and Analytical Performance

  • Sample Volume

    Sputum ≥ 0.4mL, Sediment ≥ 0.2mL

  • Specimen Types

    Raw Sputum, Sputum Sediment, Bronchoalveolar lavage (BAL)

  • Patient Collection

    Providing sufficient patient sample was collected, the cobas® MTB-RIF/INH test can be run in conjunction with cobas® MTB and cobas® MAI tests without the duplication of the pre-analytic processing

     

  • Sample Processing

    Manual liquefaction and inactivation followed by sonication and automated amplification and detection on the cobas® 6800/8800 Systems

  • PCR Target Regions

    Eighteen Rifampicin-resistance associated mutations (rpoB gene) and seven Isoniazid resistance associated mutations (katG gene and inhA gene promotor region) are detected by multiple primers and mutation specific probes.

     

  • Controls

    Internal Control ensures sample validity. Test specific Positive Control and buffer Negative Control ensures run validity.

  • Inclusivity

    rpoB gene mutations associated with rifampicin resistance:

    L511P, Q513K, Q513L, Q513P, D516V, D516Y, S522L, S522Q, H526D, H526L, H526N, H526R, H526Y, S531L, S531W, L533P

     

    katG gene mutations and inhA gene promoter region mutations associated with isoniazid resistance:

    katG gene: S315I, S315N, S315T, S315T2

    inhA gene promoter region: T-8A, T-8C, C-15T

     

    The inclusivity for two more rpoB gene mutations associated with rifampicin resistance – S522W and D516G – was verified by testing plasmids

  • Analytical Specificity

    A panel of 145 bacteria, fungi and viruses, including those commonly found in respiratory tract did not interfere with the test by generating false positive results

     

  • Analytical Sensitivity (Limit of Detection)

    RIF-resistant M. tuberculosis
        94.0 CFU/mL (sputum/BAL sediment)
        182 CFU/mL (raw sputum)
    INH-resistant M. tuberculosis
        12.6 CFU/mL (sputum/BAL sediment)
        27.5 CFU/mL (raw sputum)

  • Endogenous Interference

    Not affected by the presence of elevated levels of gastric juice, hemoglobin, human whole blood, human DNA, mucin, pus and saliva

  • Exogenous Interference

    Not affected by the presence of 48 drugs and over-the-counter substances

Clinical Performance

MTB-RIF-INH-sensitivity-and-specificity

Heteroresistance

 

The ability to detect mutant MTB in a mixed infection with wild-type MTB was confirmed by testing different mutant to wild-type ratios. Low concentration levels of MDR MTB culture isolate (~3 x LoD) in a background of up to 60% wild-type MTB are detected by cobas® MTB-RIF/INH in sputum and sediment samples.

cobas® 6800 and cobas® 8800 Systems

 

The fully automated cobas® 6800/8800 Systems offer the fastest time to results with the highest throughput and the longest walk-away time available among automated molecular platforms, providing laboratories with improved operating efficiency and the flexibility to adapt to changing testing demands.

 

Ready-to-use reagents are stored at appropriate temperatures on the system with their expiration monitored. This enables the complete mycobacteria menu comprising cobas® MTB, cobas® MAI, and cobas® MTB-RIF/INH to be seamlessly run with available menu (HIV, hepatitis, HPV and STI’s) for quality results that help speed proper treatment and reduce the spread of infection.