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Table 1 Characteristics of approved (WHO and/or FDA) molecular assays for rapid detection of MTB and drug-resistance

From: Rapid molecular assays for detection of tuberculosis

Test specification

COBAS TaqMan MTB

TB-LAMP

Xpert MTB/RIF

XpertMTB/RIF Ultra

GenoType MTBDRplus

GenoType MTBDRsl

Manufacturer

Roche Diagnostics

Eiken Chemical Co

Cepheid

Cepheid

Hain Lifescience

Hain Lifescience

Technology

Real-time PCR

Loop-mediated Isothermal amplification (LAMP)

Real-time PCR (molecular beacons)

Real-time PCR (molecular beacons)

Multiplex PCR + reverse hybridization

Multiplex PCR + reverse hybridization

Detects

MTB

MTB

MTB + RIF resistance

MTB + RIF resistance

MTB + resistance to RIF and INH

MTB diagnosis + resistance to FLQ and SLID

Target

16S rRNA

IS6110

rpoB gene

rpoB gene

rpoB, katG, inh genes

gyrA, rpo, rrs, eis genes

Time to results

2.5 h

< 1 h [41]

2 h [43]

< 90 min [58]

5 h

5 h

Approval status

FDA

WHO

WHO

WHO

WHO

WHO

Recommandations

As a confirmatory test, on smear-positive specimens

As a replacement for smear microscopy in adults or a follow-on test to smear microscopy in adults (when further testing of sputum smear-negative specimens is necessary) [41]

As the initial diagnostic test for tuberculosis in patients (adults and children) suspected of having active TB disease with either multidrug-resistant TB or HIV-associated TB [47]

As a replacement of Xpert MTB/RIF due to its greater sensitivity in detecting MTB [66]

As the initial test instead of phenotypic culture-based DST to detect resistance to RIF and INH, in persons with a sputum smear-positive specimen or a cultured isolate of MTBC, from both pulmonary and extrapulmonary sites [73].

For patients with confirmed RIF-R TB and/or MDR TB as the initial test, instead of phenotypic culture-based DST, to detect resistance to FLQ and SLID [83]

Benefits

− Does not require expensive instruments and laboratory environments

- Requires minimal expertise

- Speed and cost effective

- Requires minimal expertise

- Excellent sensitivity in tests of smear-positive sputum samples

− Improve detection of mutants at codon 533 [58]

− Differentiate silent mutations at codons 513 and 514 [58].

- Detect a hetero-resistant sample [58]

- High sensitivity for detection of RIF resistance.

- High sensitivity and specificity for detection of FLQ and SLID resistance [84].

Limitations

- Exhibits heterogeneous performance from study to study [24]

- Does not screen for any markers of drug resistance

− Requires several manual steps.

− Inferior performance in smear negatives sputum samples [102]

− False positives results due to aerosol contamination [29]

− Does not screen for any markers of drug resistance

- High costs and sophisticated hardware.

- Low sensitivity in smear-negative pulmonary samples and special populations (HIV-positives, children, extrapulmonary TB).

- Do not accommodate all mutations conferring resistance to anti-TB agents [58]

− Low specificity in patients with a recent history of TB treatment or from high-incidence countries [61].

− Should not be used as a replacement test for culture in children [65]

− Do not accommodate all mutations conferring resistance to anti-TB agents [61]

− Over diagnose the presence of MTB complex DNA in culture-negative samples [81].

− Low sensitivity to detect INH resistance.

− Complexity, the number of steps.

− Requires training for interpretation of results

− Do not perform well when applied to paucibacillary clinical specimens

− Do not accommodate all mutations conferring resistance to anti-TB agents

− Not optimal to detect resistance to KAN [84] and ethambutol [86].

− Low sensitivity in smear-negative samples [76].

− Do not accommodate all mutations conferring resistance to anti-TB agents [84].

Price per test

Not available

US$ 6

US$ 9.98

US$ 9.98

US$10

US$10

  1. US$: United States dollars
  2. hrs: hours
  3. min: minutes