cobas® MTB

A sensitive solution to a difficult diagnosis

Product image for COBAS®  MTB

A sensitive solution to a difficult diagnosis

Mycobacterium tuberculosis (TB, MTB) is a major global health problem, and is the leading cause of infectious disease deaths worldwide. This includes TB infections in people living with HIV/AIDS in which the infection is particularly lethal and difficult to detect. Early detection of TB is essential to further improve health outcomes for people with TB, and to reduce TB transmission more effectively. However, the delay in diagnosing TB and initiating appropriate medications is often long, especially in populations with poor access to health care. Tuberculosis is an airborne mycobacterial infection caused by the M. tuberculosis complex (MTBC). MTBC is spread from one person to another through tiny droplets released into the air via coughs and sneezes. Resulting infection generally affects the lungs, but can also affect other parts of the body. Screening for active TB in selected risk groups is recommended by the WHO and CDC to improve early TB detection. More specifically, the CDC and WHO recommend performing a diagnostic nucleic acid amplification test from all patients suspected of having pulmonary TB. Additionally, WHO guidelines recommend all persons living with HIV/AIDS should be tested for MTB. cobas® MTB provides a sensitive solution to facilitate this difficult diagnosis, providing important information for patient care decisions.


cobas® MTB includes a dual-target approach for detection of M. tuberculosis. Selective amplification of target nucleic acid from the sample is achieved by the use of target-specific forward and reverse primers for the MTB complex which are selected from highly-conserved regions within the respective target organism. MTB is detected by two selective sets of primers and two probes targeting separated regions (dual-target, 16S rRNA gene and esx genes - esxJ, esxK, esxM, esxP, and esxW).

cobas MTB assay performance
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.

Intended Use

cobas® MTB for use on the cobas® 5800/6800/8800 Systems is an automated, qualitative in vitro diagnostic test, that utilizes real-time polymerase chain reaction (PCR), for the direct detection of Mycobacterium tuberculosis complex (MTBC) DNA in either acid-fast bacilli (AFB) smear-positive or smear-negative, human respiratory specimens; including raw sputum, and digested and decontaminated (N-acetyl-L-cysteine/NaOH [NALC-NaOH]-treated) sputum and bronchoalveolar lavage (BAL) samples.


This test is for use with specimens from patients who are suspected of Mycobacterium tuberculosis infection, and who are not taking antituberculosis therapy. This test is intended for the aid of pulmonary tuberculosis diagnosis, and in conjunction with culture and other laboratory findings, as well as clinical signs and symptoms.


Registration Status

CE-IVD, not approved in the US

Package Inserts

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

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 test can be run in conjunction with cobas® MAI and cobas® MTB-RIF/INH 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® 5800/6800/8800 Systems




  • PCR Target Regions

    Dual target amplification of 16S rRNA gene and esx genes - esxJ, esxK, esxM, esxP, and esxW

  • Controls

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

  • Inclusivity

    M. tuberculosis (12 strains), M. bovis BCG (2 strains), M. africanum, M. bovis subsp. bovis, M. canetti, M. caprae, M. microti, M. orygis, M. pinnipedii, M. suricattae

  • Analytical Specificity

    A panel of 178 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)

    M. tuberculosis
        7.6 CFU/mL (sputum/BAL sediment)
        8.8 CFU/mL (raw sputum)
    M. bovis BCG
        0.9 CFU/mL (sputum/BAL sediment)
        1.0 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

Sensitivity and specificity of cobas® MTB using clinical samples

cobas® MTB
Sensitivity Raw Sputum
C+/S- 116/134
86.6 %
(79.6 - 91.8 %)
C+/S+ 275/278
98.9 %
(96.9 - 99.7 %)
C+/S± 391/412
94.9 %
(92.3 - 96.8 %)
Sediment C+/S-

78.4 %
(70.9 - 84.7 %)
99.3 %
(97.5 - 99.9 %)

92.2 %
(89.3 - 94.5 %)
Specificity Raw Sputum C-/S- 328/332
98.2 %
(96.1 - 99.3 %)
Sediment C-/S- 381/393
96.9 %
(94.7 - 98.4 %)

C = Culture, S = AFB smear


  1. World Health Organization. Global tuberculosis report 2018. Geneva, Switzerland; WHO, 2018.