Line probe assays (LPAs) for tuberculosis were endorsed by the WHO in 2008 for molecular detection of drug resistance from smear-positive patients at risk of Multi Drug Resistant-Tuberculosis (MDRTB) Two commercial LPAs are currently available: INNO-LiPA Rif.TB test (Innogenetics NV, Gent, Belgium) and GenoType MTBDRplus test (Hain Lifescience GmbH, Nehren, Germany). Line Probe Assays for tuberculosis uses PCR/hybridization technique to identify members of the Mycobacterium Tuberculosis while simultaneously identifying drug-resistant strains by detecting the most common single nucleotide polymorphorisms (SNPs) associated with resistance. Meta-analyses have shown that LPAs are highly accurate for the detection of first-line drug resistance, especially in smear-positive sputum specimens. WHO analysis of systematic reviews and meta-analyses showed that Line probe assays for tb are highly sensitive (≥97%) and specific (≥99%) for the detection of RIF resistance (Rifampicin resistance), alone or in combination with Isoniazid also known as isonicotinylhydrazine (INH) (sensitivity ≥90%; specificity ≥99%), on isolates of M. tuberculosis and on smear-positive sputum specimens. Accuracy for detection of Multi Drug Resistant-TB was 99%, which remained unchanged when RIF resistance alone was used as a proxy marker for MDR-TB. Hain Lifesciences released the GenoType MTBDRsl test in 2009, designed to test for resistance to second-line anti-TB drugs (fluoroquinolones, ethambutol, aminoglycosides and cyclic peptides), and which can be used in combination with the MTBDRplus test to identify XDR-TB. Advantages of Line Probe Assay for tuberculosis It can be tested directly in smear-positive sputum samples. It gives rapid drug susceptibility results without the need for culture. LPAs can be used as the primary method for Drug Susceptibility Test on cultured isolates of M. tuberculosis, replacing phenotypic DST. Disadvantages The major disadvantages of LPAs are It is labour intensive It require highly trained personnel and dedicated laboratory space and equipment. References www.who.int/tb/features http://www.medscape.com/viewarticle/740253_9 http://www.finddiagnostics.org/programs/tb/find_activities/line_probe_assay_1.html www.biomedcentral.com/content/pdf/1471-2334-10-41.pdf www.pulmononline.org/pdf/5026360sa-01.pdf Got something to say about this post? Leave a comment...your comments are valuable for improving the posts.