Table 3 characteristics of molecular assays for rapid detection of MTB and drug-resistance, not yet approved by WHO and/or FDA
Test specification | PURE TB-LAMP | FluoroType MTB | EasyNAT TB | Xpert Omni | Xpert XDR |
|---|---|---|---|---|---|
Manufacturer | Eiken Chemical Co | Hain Lifescience | Ustar | Cepheid | Cepheid |
Technology | Procedure for Ultra Rapid Extraction Loop-mediated isothermal amplification | Real-time PCR (HyBeacon fluorescence) | Isothermal DNA amplification Lateral flow | Real-time PCR (molecular beacons) | Real-time PCR (molecular beacons) |
Detects | MTB | MTB | MTB | MTB + RIF resistance | MTB + resistance to INH, FLQ and SLID |
Time to results | 90 min [90] | 3 h | 90 min | ∼ 110 min [67] | 90 min |
Current status | The assay is now on path for WHO review | CE-IVD marked | CE-IVD certified Approved by China FDA | Platform under development. Launch expected at the end of 2018. | Assay under development. |
Benefits | − Performed quickly [36]. − No sophisticated laboratory equipment is needed [36]. − Requires fewer procedures and consumables. − Sensitivity higher than smear microscopy [36] | − Fluorocycler system is suitable for low number of samples or for large series [92]. − Sensitivity equivalent to other molecular tests. | − Requires basic laboratory equipment | − Point of care − Performed quickly [95]. | Assay under development. |
Limitations | − Yield false-negative results [90] − Possible risks for cross contamination. − Does not screen for any markers of drug resistance. − Further studies are required [98]. | − Low specificity due to DNA contamination [94] − Low sensitivity in smear-negative [92]. − Does not screen for any markers of drug resistance. - Further studies are required [92]. | − Not suitable for diagnosis of extrapulmonary TB [100]. − Does not screen for any markers of drug resistance. | − Processes one sample at a time [95] − Cost and accessibility will limit adoption in high-endemic areas − Do not accommodate all mutations conferring resistance to anti-TB agents | Assay under development. |
Price per test | Not available | Not available | US$ 6–8 | Not available | Not available |