Performance Of Line Probe Assay Research Articles

Comparative Performance of Line Probe Assay and GeneXpert in the Detection of Rifampicin Monoresistance in a TB-Endemic African Country.

Rapid, accurate and reliable assays are required for timely detection of drug-resistant tuberculosis and early initiation of second-line TB treatment as well as to minimize transmission of resistant strains. This study assessed diagnostic performance characteristics of two rapid molecular assays, line probe assay (LPA) and GeneXpert (MTB/RIF), in the detection rifampicin monoresistance using the phenotypic proportion method on Lowenstein-Jensen media as the gold standard. This study involved a total of 357 isolates, 74 rifampicin-resistant and 283 rifampicin-susceptible, collected at the Central Tuberculosis Reference Laboratory (CTRL) in Dar es Salaam, Tanzania, between 2016 and 2019. Sensitivity, specificity and positive and negative predictive values were used to assess the performance characteristics of the two assays while kappa coefficient was used to determine agreement of test results. The receiver operating curve (ROC) was used to determine the discriminatory ability of the test in distinguishing resistant and susceptible TB isolates. Our results showed that GeneXpert had sensitivity, specificity and positive and negative predictive values of 93.2, 82.7, 58.5 and 97.9%, respectively; the corresponding performance for LPA was 86.5, 97.5, 90.1 and 96.5%, respectively. Compared with conventional phenotypic DST results, GeneXpert had a moderate agreement (kappa 0.621, p < 0.001), while LPA had high agreement (0.853, p < 0.001). LPA showed an accuracy of 95.2% compared to GeneXpert's 84.9%. ROC curve depicted the ability of the tests to distinguish rifampicin-sensitive and rifampicin-resistant strains to be 87.9% for GeneXpert and 92.0% for LPA. Our results indicate the superiority of LPA over GeneXpert regarding detection of rifampicin monoresistance. However, logistic challenges such as longer turnaround time and need for skilled laboratory personnel may limit its use.

Utility of line probe assay in detecting drug resistance and the associated mutations in patients with extrapulmonary tuberculosis in Addis Ababa, Ethiopia.

Introduction:Molecular tests allow rapid detection of Mycobacterium tuberculosis and drug resistance in a few days. Identifying the mutations in genes associated with drug resistance may contribute to the development of appropriate interventions to improve tuberculosis control. So far, there is little information in Ethiopia about the diagnostic performance of line probe assay (LPA) and the M. tuberculosis common gene mutations associated with drug resistance in extrapulmonary tuberculosis. Thus, this study aimed to assess the frequency of drug resistance-associated mutations in patients with extrapulmonary tuberculosis (EPTB) and to compare the agreement and determine the utility of the genotypic in the detection of drug resistance in Addis Ababa, Ethiopia.Methods:A cross-sectional study was conducted on stored M. tuberculosis isolates. The genotypic and phenotypic drug susceptibility tests were performed using LPA and BACTEC-MGIT-960, respectively. The common mutations were noted, and the agreement and the utility of the LPA were determined using the BACTEC-MGIT-960 as a gold standard.Results:Of the 151 isolates, the sensitivity and specificity of MTBDRplus in detecting isoniazid resistance were 90.9% and 100%, respectively. While for rifampicin, it was 100% and 99.3% for sensitivity and specificity, respectively. The katG S315Tl was the most common mutation observed in 85.7% of the isoniazid-resistant isolates. In the case of rifampicin, the most common mutation (61.9%) was observed at position rpoB S531L. Mutations in the gyrA promoter region were strongly associated with Levofloxacin and Moxifloxacin resistance.Conclusion:Line probe assay has high test performance in detecting resistance to anti-TB drugs in EPTB isolates. The MTBDRplus test was slightly less sensitive for the detection of isoniazid resistance as compared to the detection of rifampicin. The most prevalent mutations associated with isoniazid and rifampicin resistance were observed at katG S315Tl and rpoB S531L respectively. Besides, all the fluoroquinolone-resistant cases were associated with gyrA gene. Finally, a validation study with DNA sequencing is recommended.

Diagnostic Performance of Line Probe Assay for the Diagnosis of Rifampicin and Isoniazid ‎Resistant Tuberculosis in a Resource-Poor Country ‎

Background and study aim: The use of LPA is still new in Nigeria and only available in TB reference laboratories. In this ‎study, the performance of LPA version 2.0 was evaluated for the detection of resistant to first-line ‎anti-TB drugs‎‎‎. Patients and Methods: ‎We evaluated the performance of LPA version 2.0 for the detection of rifampicin (RIF) and ‎isoniazid (INH) resistance. Sputum samples from 223 participants were subjected to phenotypic ‎drug susceptibility testing (PDST) and LPA. Statistical analyses included calculation of sensitivity, ‎specificity, positive and negative predictive values. Cross tabulation was done along the kappa test ‎to measure the degree of agreement between PDST and LPA. P-Value > 0.05 was considered ‎significant‎.‎ Results: The overall sensitivity and specificity of 89.6% (95% C.I 82.5-94.5%) and 65.4% (95% C.I 44.3-‎‎82.7%) for detection of RIF resistance; for INH they were 76.6 (95% C.I 67.5-84.5%) and 76.7% ‎‎(95% C.I 49.5-82.6%); and for MDR-TB, they were 67.0% (95% C.I 56.4-76.5%) and 72.0% ‎‎(95% C.I 57.6-83.7%). The kappa values were 0.53 (0.001), 0.38 (p = 0.000) and 0.36 (p = 0.000) ‎for the detection of RIF, INH and MDR-TB. There was moderate agreement between PDST and ‎LPA for detection of RIF (κ = 0.57; P = 0.0001), INH (κ = 0.44; P = 0.0001), MDR-TB (κ = 0.43; ‎P = 0.001)‎‎. Conclusion: The Line probe assay has good sensitivity and specificity for detecting rifampicin and isoniazid. ‎However, the overall performance is moderate; this should be considered when interpreting the ‎assay’s results‎‎‎‎.

Comparative Performance of Line Probe Assay (Version 2) and Xpert MTB/RIF Assay for Early Diagnosis of Rifampicin-Resistant Pulmonary Tuberculosis.

BackgroundThe emergence of drug-resistant tuberculosis (TB), is a major menace to cast off TB worldwide. Line probe assay (LPA; GenoType MTBDRplus ver. 2) and Xpert MTB/RIF assays are two rapid molecular TB detection/diagnostic tests. To compare the performance of LPA and Xpert MTB/RIF assay for early diagnosis of rifampicin-resistant (RR) TB in acid-fast bacillus (AFB) smear-positive and negative sputum samples.MethodsA total 576 presumptive AFB patients were selected and subjected to AFB microscopy, Xpert MTB/RIF assay and recent version of LPA (GenoType MTBDRplus assay version 2) tests directly on sputum samples. Results were compared with phenotypic culture and drug susceptibility testing (DST). DNA sequencing was performed with rpoB gene for samples with discordant rifampicin susceptibility results.ResultsAmong culture-positive samples, Xpert MTB/RIF assay detected Mycobacterium tuberculosis (Mtb ) in 97.3% (364/374) of AFB smear-positive samples and 76.5% (13/17) among smear-negative samples, and the corresponding values for LPA test (valid results with Mtb control band) were 97.9% (366/374) and 58.8% (10/17), respectively. For detection of RR among Mtb positive molecular results, the sensitivity of Xpert MTB/RIF assay and LPA (after resolving discordant phenotypic DST results with DNA sequencing) were found to be 96% and 99%, respectively. Whereas, specificity of both test for detecting RR were found to be 99%.ConclusionWe conclude that although Xpert MTB/RIF assay is comparatively superior to LPA in detecting Mtb among AFB smear-negative pulmonary TB. However, both tests are equally efficient in early diagnosis of AFB smear-positive presumptive RR-TB patients.

Feasibility of Direct Sputum Molecular Testing for Drug Resistance as Part of Tuberculosis Clinical Trials Eligibility Screening.

A rapid diagnosis of drug-resistant tuberculosis (TB) is critical for early initiation of effective therapy. Molecular testing with line probe assays (MTBDRplus and MTBDRsl) on culture isolates has been available for some time and significantly reduces the time to diagnosis of drug resistance. However, routine use of this test directly on sputum is less common. As part of enrollment screening procedures for tuberculosis clinical trials conducted in Hanoi, Vietnam, we evaluated the feasibility and performance of line probe assay (LPA) testing directly on sputum samples from 315 participants with no prior history of TB treatment. Test performance characteristics for the detection of rifampin (RIF) and isoniazid (INH) drug resistance as compared to culture-based drug susceptibility testing (DST) reference standard were calculated. LPA demonstrated high sensitivity and specificity for the diagnosis of drug resistance. Scaling up molecular testing on sputum as part of time-sensitive clinical trial screening procedures in high TB burden settings is feasible and will reduce both time to initiation of appropriate therapy and the risk of late exclusions due to microbiologic ineligibility.

The diagnostic utility of line probe assays for multidrug-resistant tuberculosis

Owing to the burden of multidrug-resistant tuberculosis, molecular techniques have been approved by the WHO for the rapid diagnosis of the same. The objectives of this prospective, diagnostic study, conducted at Christian Medical College, a tertiary care center in South India, were to compare the performance of line probe assay (GenoTypeMTBDRplus) with culture, as well as the Xpert MTB/Rif assay on sputum samples. Ninety-one consecutive suspects of multidrug-resistant pulmonary tuberculosis patients from January 2013 to June 2013 were enrolled in this study and the results of line probe assay compared to culture and Xpert MTB/Rif. Compared to culture, the assay demonstrated a sensitivity and specificity of 81.5% (95%CI 67.4–91.1%) and 87.5% (95%CI 71–96.5%) for the detection of tuberculosis, with sensitivity and specificity of 100% (95%CI 85.2–100%) and 93.8% (95%CI 69.8–99.8%), respectively, for rifampicin resistance. For isoniazid resistance, sensitivity and specificity were 89.3% (95%CI 71.8–97.7%) and 100% (95%CI 71.5–100%), respectively. Compared to Xpert MTB/Rif assay, the assay showed a sensitivity of 80% (95%CI 68.2–88.9%) and specificity of 100% (95%CI 85.8–100%) for the detection of tuberculosis a sensitivity of 94.3% (95%CI 80.8–99.3%) and specificity of 94.1% (95%CI 71.3–99.9%) for rifampicin resistance was attained. This assay performed well on smear positive samples, but poorly on smear negative and scanty samples, and can serve as a rapid diagnostic tool, particularly in isoniazid monoresistant cases of tuberculosis, which are not diagnosed by Xpert MTB/Rif.

Comparative Evaluation of GenoType MTBDRplus Line Probe Assay with Solid Culture Method in Early Diagnosis of Multidrug Resistant Tuberculosis (MDR-TB) at a Tertiary Care Centre in India

BackgroundThe objectives of the study were to compare the performance of line probe assay (GenoType MTBDRplus) with solid culture method for an early diagnosis of multidrug resistant tuberculosis (MDR-TB), and to study the mutation patterns associated with rpoB, katG and inhA genes at a tertiary care centre in north India.MethodsIn this cross-sectional study, 269 previously treated sputum-smear acid-fast bacilli (AFB) positive MDR-TB suspects were enrolled from January to September 2012 at the All India Institute of Medical Sciences hospital, New Delhi. Line probe assay (LPA) was performed directly on the sputum specimens and the results were compared with that of conventional drug susceptibility testing (DST) on solid media [Lowenstein Jensen (LJ) method].ResultsDST results by LPA and LJ methods were compared in 242 MDR-TB suspects. The LPA detected rifampicin (RIF) resistance in 70 of 71 cases, isoniazid (INH) resistance in 86 of 93 cases, and MDR-TB in 66 of 68 cases as compared to the conventional method. Overall (rifampicin, isoniazid and MDR-TB) concordance of the LPA with the conventional DST was 96%. Sensitivity and specificity were 98% and 99% respectively for detection of RIF resistance; 92% and 99% respectively for detection of INH resistance; 97% and 100% respectively for detection of MDR-TB. Frequencies of katG gene, inhA gene and combined katG and inhA gene mutations conferring all INH resistance were 72/87 (83%), 10/87 (11%) and 5/87 (6%) respectively. The turnaround time of the LPA test was 48 hours.ConclusionThe LPA test provides an early diagnosis of monoresistance to isoniazid and rifampicin and is highly sensitive and specific for an early diagnosis of MDR-TB. Based on these findings, it is concluded that the LPA test can be useful in early diagnosis of drug resistant TB in high TB burden countries.