Multicenter evaluation of Seegene Anyplex TB PCR for the detection of Mycobacterium tuberculosis in respiratory specimens

Evaluation of seegene anyplex MTB/NTM real-time detection assay for diagnosis of tuberculous meningitis

BACKGROUND

Tuberculous meningitis (TBM) is a common central nervous system infectious disease. Polymerase chain reaction (PCR) assay is a useful method for the rapid diagnosis of TBM. The Seegene Anyplex MTB/NTM real-time detection assay has good sensitivity and specificity for detection of tuberculosis in respiratory specimens, though, data regarding other specimens are lacking. This study aims to define the diagnostic role of Seegene Anyplex MTB/NTM real-time detection assay in TBM in adults.

METHODS

This was a retrospective study of 367 adults with symptomatic community acquired meningitis between December 2013 and December 2019. Cerebrospinal fluid (CSF) had been sent for conventional diagnosis, including culture to identify Mycobacterium tuberculosis, and Seegene Anyplex MTB/NTM real-time detection assay. Other diagnostic examinations were performed as necessary.

RESULTS

Of the 367 patients in the study, 37 were diagnosed with TBM (14 with definite TBM and 23 with probable TBM). Between the total TBM cases (n = 37) and non-TBM cases (n = 330), clinical sensitivity was 32.4% and specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 93.0%. Between the definite TBM cases (n = 14) and non-TBM cases (n = 330), clinical sensitivity was 50.0% and specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 97.9%.

CONCLUSION

Due to lack of sensitivity, we suggest Seegeen Anyplex MTB/NTM real-time detection assay should not be used to rule out TBM but is useful for definite diagnosis.

Diagnostic Accuracy of Loop-Mediated Isothermal Amplification (TB-LAMP) for Tuberculosis in Children

BACKGROUND

Diagnosing tuberculosis (TB) in children is challenging due to its paucibacillary nature. Loop-mediated isothermal amplification (TB-LAMP) is a simple, rapid, and specific point-of-care molecular diagnostic test. However, evaluation of its performance remains limited in children. This study aimed to evaluate the diagnostic performance of Eiken TB-LAMP among children with presumed tuberculosis disease.

METHODS

Pulmonary and extrapulmonary specimens were collected from children under 18 years with presumed TB. Each specimen was tested by using TB-LAMP, acid-fast bacilli (AFB) smear microscopy, and one of the two molecular assays (polymerase chain reaction [PCR] or Xpert MTB/RIF). Sensitivity and specificity were estimated compared to mycobacterial culture as reference standard.

RESULTS

From January 2020 to January 2021, 75 participants with presumed TB were enrolled with median age of 7 years (IQR 2-12). Seventeen specimens from 16 (21.3%) children had bacteriologically confirmed TB: 10 pulmonary and 7 extrapulmonary specimens. Overall sensitivity and specificity of TB-LAMP was 76.5% (95% CI 50.1%-93.2%) and 100% (95% CI 94.3%-100%), respectively. It had significantly higher sensitivity than AFB (52.9%, 95% CI 27.8%-77.0%) and similar to other molecular assays; PCR 82.4% (95% CI 56.6%-96.2%), Xpert MTB/RIF 70.0% (95% CI 34.8%-93.3%). Sensitivity of TB-LAMP for pulmonary, lymph node tissue, and extrapulmonary fluid was 80% (95% CI 44.4%-97.5%), 100% (95% CI 39.8-100), and 33.3% (95% CI 0.8-90.6), respectively. TB-LAMP detected all smear-positive (N = 9) and 50% of smear-negative (N = 8) specimens.

CONCLUSIONS

TB-LAMP had higher sensitivity than AFB microscopy and accuracy similar to other molecular assays in both pulmonary and extrapulmonary specimens. These findings support using TB-LAMP as a point-of-care test in children.

Evaluation of an in-house loop-mediated isothermal amplification for Mycobacterium tuberculosis detection in a remote reference laboratory, Thailand

Loop-mediated isothermal amplification (LAMP) is a simple and efficient nucleic acid amplification method for the rapid diagnosis of infectious diseases. This study assessed the performance of an in-house LAMP for tuberculosis (TB) diagnosis at a remote reference laboratory in the endemic setting of Thailand. As part of the routine service, 1,882 sputum samples were processed for mycobacterial culture in Lowenstein-Jensen and MGIT media. The DNA was extracted from the remaining decontaminated samples after the culture procedure for real-time polymerase chain reaction (PCR) analysis using Anyplex plus MTB/NTM detection kit. 785 (40.28%) were positive by mycobacterial culture. Of these, 222 DNA remnants were available and subjected to LAMP analysis. Based on culture as reference (Mycobacterium tuberculosis; MTB= 209/ non-tuberculous mycobacteria; NTM= 13), the overall sensitivity of LAMP and Anyplex plus assays for MTB detection were 89.95% (188/209; 95% confidential interval [CI]: 85.05-93.67%) and 96.65% (202/209; 95% CI: 93.22-98.64%), and the accuracy values were 88.74% (197/222; 95% CI: 83.83-92.58) and 96.40% (214/222; 93.02-98.43%), respectively. The sensitivity and accuracy of the in-house LAMP and the Anyplex plus real-time PCR assay were high in comparison to culture results. The high sensitivity and accuracy suggested that this in-house LAMP was promising and might be useful for early TB diagnosis.

Clinical evaluation of the T-SPOT.TB test for detection of tuberculosis infection in northeastern Guangdong Province, China

OBJECTIVE

We evaluated clinical performance of the T-SPOT.TB test for detecting tuberculosis (TB) infection in Meizhou, China.

METHODS

We enrolled 2,868 patients who underwent T-SPOT.TB, smear, and TB-DNA at the same time. The tests' sensitivity and specificity were evaluated and compared in different groups, and in pulmonary TB (PTB) and extrapulmonary TB (EPTB) subgroups. Receiver operator characteristic (ROC) curve analysis was used to evaluate T-SPOT.TB's diagnostic value and determine its cutoff value.

RESULTS

T-SPOT.TB, TB-DNA, and sputum smear sensitivity was 61.44%, 37.12%, and 14.02%; and specificity was 76.49%, 99.20% and 99.60%, respectively. The T-SPOT.TB positive rate was higher in the PTB and EPTB subgroups than in patients with other pulmonary diseases (61.38% and 61.76% vs. 23.34%). The T-SPOT.TB test had better diagnostic accuracy and sensitivity when the positive cutoff value of marker ESAT-6 was 2.5 [area under ROC curve = 0.701, 95%CI 0.687-0.715] and marker CFP-10 was 6.5 [area under ROC curve = 0.669, 95%CI 0.655-0.683].

CONCLUSION

T-SPOT.TB sensitivity was higher than that of TB-DNA or sputum smear, but the specificity was lower. T-SPOT.TB had moderate sensitivity and specificity for diagnosing TB. T-SPOT.TB's new positive cutoff value may be clinically valuable according to ROC analysis.

Evaluation of a semi-automated Seegene PCR workflow with MTB, MDR, and NTM detection for rapid screening of tuberculosis in a low-prevalence setting

In areas of low tuberculosis (TB) prevalence, laboratory diagnosis of TB may essentially cover non-tuberculous mycobacteria (NTM) in addition to Mycobacterium tuberculosis (MTB). In this study, a semi-automated PCR workflow distinguishing MTB and NTM (Anyplex™ MTB/NTMe, Seegene) and subsequently detecting MTB isoniazid/rifampicin resistance (Allplex™ MTB/MDRe, Seegene) was evaluated for replacing smear microscopy of acid-fast bacilli as the rapid screening method for TB. With 279 clinical samples, 47 cultures positive for MTB and 76 for NTM, the Anyplex™ MTB/NTMe assay and smear microscopy showed equal sensitivities (49.6% vs 50.8%, respectively) but Anyplex™ MTB/NTMe was more sensitive for MTB (63.8% vs 25.6%) than for NTM (40.8% vs 64.5%). Allplex™ MTB/MDRe showed a slightly higher sensitivity of 68.1% for MTB (32/47 positive, n = 222). Antibiotic resistance profiles were correctly identified for all MTB isolates (one MDR isolate). Specificity was 100% for both assays. Anyplex™ MTB/NTMe detected all the 18 NTM species present in the study. The analytical performance of the evaluated high-throughput workflow was relatively weak compared to culture but potentially adequate as a rapid screening method analogous to smear microscopy with additional differentiation between TB, MDR-TB, and NTM.

Evaluation of Anyplex™ II MTB/MDR kit's performance to rapidly detect isoniazid and rifampicin resistant Mycobacterium tuberculosis from various clinical specimens

To determine the accuracy of multiplex real-time PCR (Anyplex™ II MTB/MDR kit) in detecting Isoniazid (INH)- and Rifampin (RIF)-resistant Mycobacterium tuberculosis strains from various clinical specimens. The performance of Anyplex™ II MTB/MDR kit in detecting INH- and RIF-resistant M. tuberculosis compared to the conventional drug susceptibility tests by Mycobacterial Growth Indicator Tube (MGIT). A total of 430 clinical samples had positive results for M. tuberculosis from both Anyplex™ II MTB/MDR kit assay and mycobacterial cultures by MGIT method. When compared to MGITs, the sensitivity and specificity of Anyplex™ II MTB/MDR kit in detecting INH-resistant TB were 85.71% and 99.75%, respectively. For the detection of MDR-TB, the sensitivity and specificity of the test were 82.35% and 99.76%, respectively. The positive predictive values and negative predictive values to detect INH-resistant TB were 96.77% and 98.75%, respectively. Anyplex™ II MTB/MDR kit can be used to rapidly detect isoniazid and rifampicin resistances. It has a high sensitivity, specificity and PPV in detecting INH-resistant TB and MDR-TB. This test can be used as an alternative test to Xpert MTB/RIF because it can rapidly detect both INH-resistant TB and RIF-resistant TB.

Comparison of the Genedia MTB/NTM Detection Kit and Anyplex plus MTB/NTM Detection Kit for detection of Mycobacterium tuberculosis complex and nontuberculous mycobacteria in clinical specimens

BACKGROUND

Real-time (RT) PCR is a rapid and accurate method that is widely used for the detection of Mycobacterium tuberculosis complex (MTB). The aim of this study was to evaluate and compare the performance of the Genedia MTB/NTM Detection Kit and the Anyplex plus MTB/NTM Detection kit in the detection of MTB and nontuberculous mycobacteria (NTM) in clinical specimens.

METHODS

From October 2017 to February 2018, 236 respiratory specimens and 137 non-respiratory specimens, from patients with suspected tuberculosis, were examined. AFB smear, culture, and RT-PCR using the Genedia MTB/NTM Detection kit (Green Cross Medical Science Corp.) and the Anyplex plus MTB/NTM Detection kit (Seegene) were applied. PCR performance in the detection of MTB and NTM was evaluated in relation to culture results and between the two assays.

RESULTS

Culture was positive for MTB in 30 (8.0%) of the 373 specimens and for NTM in 23 (6.2%). The sensitivity and specificity of MTB detection with the Genedia kit were 76.7% and 99.7%, respectively, whereas the Anyplex kit sensitivity and specificity for MTB detection were 86.7% and 97.5%, respectively. Both kits exhibited the same sensitivity (73.9%) for NTM detection, and the specificity was 100% and 99.4% for the Genedia and Anyplex kits, respectively.

CONCLUSIONS

The Genedia and Anyplex kits demonstrated high sensitivity and specificity for the detection of MTB and NTM. Both kits have a high concordance rate and can be used more widely in clinical laboratories for the early detection of tuberculosis.

Evaluation of EZplex MTBC/NTM Real-Time PCR kit: diagnostic accuracy and efficacy in vaccination

Purpose

Tuberculosis (TB) is mainly caused by Mycobacterium tuberculosis, which is a pathogenic mycobacterial species grouped under Mycobacterium tuberculosis complex (MTBC) with four other pathogenic mycobacterial species. The mycobacteria not included in MTBC are known as nontuberculous mycobacteria (NTM), and cause several pulmonary diseases including pneumonia. Currently, NTM occurrences in TB-suspected respiratory specimens have increased, due to which, precise detection of MTBC and NTM is considered critical for the diagnosis and vaccination of TB. Among the various methods available, real-time PCR is frequently adopted for MTBC/NTM detection due to its rapidness, accuracy, and ease of handling. In this study, we evaluated a new real-time PCR kit for analytical and clinical performance on sputum, bronchial washing, and culture specimens.

Materials and Methods

For assessing its analytical performance, limit of detection (LOD), reactivity, and repeatability test were performed using DNA samples. To evaluate clinical performance, 612 samples were collected and clinically tested at a tertiary hospital.

Results

LOD was confirmed as 0.584 copies/µL for MTBC and 47.836 copies/µL for NTM by probit analysis (95% positive). For the reactivity test, all intended strains were detected and, in the repeatability test, stable and steady results were confirmed with coefficient of variation ranging from 0.36 to 1.59. For the clinical test, sensitivity and specificity were 98.6%–100% and 98.8%–100% for MTBC and NTM, respectively.

Conclusion

The results proved the usefulness of the kit in TB diagnosis. Furthermore, it could be adopted for the assessment of vaccine efficacy.

Comparison of DNA extraction methods for drug susceptibility testing by allele-specific primer extension on a microsphere-based platform: Chelex-100 (in-house and commercialized) and MagPurix TB DNA Extraction Kit

Tuberculosis (TB), caused by infections of the Mycobacterium tuberculosis (MTB) complex, is the ninth leading cause of death worldwide, and several molecular approaches for MTB species identification and the detection of mutations associated with drug resistance have been developed to date. We previously developed a diagnostic assay for drug susceptibility testing that can detect mutations conferring resistance to anti-TB drugs using allele-specific primer extension on a microsphere-based platform for multiplex polymerase chain reaction. The aim of the present study was to optimize this diagnostic assay based on the evaluation of three methods for extracting mycobacterial DNA from clinical samples. Mycobacterial DNA of 81 samples was digested and decontaminated by N-acetyl-l-cysteine-2% NaOH and then extracted using three methods: "in-house" 5% Chelex-100 chelating resin, InstaGene Matrix, and MagPurix TB DNA Extraction Kit. The former two methods are manual extraction methods, whereas the MagPurix TB DNA Extraction Kit is an automated extraction method used with the MagPurix 12 s automated nucleic acid purification system. The extracted DNA was then subjected to our diagnostic assay, and the results were compared among methods. The magnetic bead method exhibited a higher extraction efficiency and resulted in greater diagnostic efficacy than the two resin-based methods with respect to both target gene detection and acid-fast bacilli smear grades. Therefore, the MagPurix TB DNA Extraction Kit is the optimal MTB DNA extraction method for our diagnostic assay of TB drug susceptibility testing.

A case of pulmonary infection caused by Mycobacterium asiaticum: Difficulties on diagnostic and therapeutic approaches

A 56-year-old previously healthy female presented with chronic productive cough and fever. Chest X-ray revealed right middle lung opacities. Sputum acid fast bacilli smear was positive, however polymerase chain reaction was negative for Mycobacterium tuberculosis. Further investigations were pursued, which identified Mycobacterium asiaticum. Appropriate therapy with isoniazid, rifampin and clarithromycin for total 18 months (including pyrazinamide and ethambutol for first 4 months) resulted in clinical and radiographic improvement. Recognition of the possibility of this rarely described pulmonary pathogen is essential for successful treatment.

Improved performance of the artus Mycobacterium tuberculosis RG PCR kit in a low incidence setting: a retrospective monocentric study

Tuberculosis (TB) and the spread of Mycobacterium tuberculosis complex (MTBC) strains resistant against rifampin (RIF) and isoniazid (INH) pose a serious threat to global health. However, rapid and reliable MTBC detection along with RIF/INH susceptibility testing are challenging in low prevalence countries due to the higher rate of false positives. Here, we provide the first performance data for the artus MTBC PCR assay in a low prevalence setting. We analyze 1323 respiratory and 311 non-respiratory samples with the artus MTBC PCR assay as well as by mycobacterial culture and microscopy. We propose retesting of specimens in duplicate and consideration of a determined cycle-threshold value cut-off greater than 34, as this significantly increases accuracy, specificity, and negative predictive value without affecting sensitivity. Furthermore, we tested fourteen MTBC positive samples with the GenoType MTBDRplus test and demonstrate that using an identical DNA extraction protocol for both assays does not impair downstream genotypic testing for RIF and INH susceptibility. In conclusion, our procedure optimizes the use of the artus MTB assay with workload efficient methods in a low incidence setting. Combining the modified artus MTB with the GenoType MTBDRplus assays allows rapid and accurate detection of MTBC and RIF/INH resistance.

Effectiveness of real-time polymerase chain reaction assay for the detection of Mycobacterium tuberculosis in pathological samples: a systematic review and meta-analysis

BACKGROUND

Rapid and accurate diagnosis of tuberculosis (TB) is key to manage the disease and to control and prevent its transmission. Many established diagnostic methods suffer from low sensitivity or delay of timely results and are inadequate for rapid detection of Mycobacterium tuberculosis (MTB) in pulmonary and extra-pulmonary clinical samples. This study examined whether a real-time polymerase chain reaction (RT-PCR) assay, with a turn-a-round time of 2 h, would prove effective for routine detection of MTB by clinical microbiology laboratories.

METHODS

A systematic literature search was performed for publications in any language on the detection of MTB in pathological samples by RT-PCR assay. The following sources were used MEDLINE via PubMed, EMBASE, BIOSIS Citation Index, Web of Science, SCOPUS, ISI Web of Knowledge and Cochrane Infectious Diseases Group Specialised Register, grey literature, World Health Organization and Centres for Disease Control and Prevention websites. Forty-six studies met set inclusion criteria. Generated pooled summary estimates (95% CIs) were calculated for overall accuracy and bivariate meta-regression model was used for meta-analysis.

RESULTS

Summary estimates for pulmonary TB (31 studies) were as follows: sensitivity 0.82 (95% CI 0.81-0.83), specificity 0.99 (95% CI 0.99-0.99), positive likelihood ratio 43.00 (28.23-64.81), negative likelihood ratio 0.16 (0.12-0.20), diagnostic odds ratio 324.26 (95% CI 189.08-556.09) and area under curve 0.99. Summary estimates for extra-pulmonary TB (25 studies) were as follows: sensitivity 0.70 (95% CI 0.67-0.72), specificity 0.99 (95% CI 0.99-0.99), positive likelihood ratio 29.82 (17.86-49.78), negative likelihood ratio 0.33 (0.26-0.42), diagnostic odds ratio 125.20 (95% CI 65.75-238.36) and area under curve 0.96.

CONCLUSIONS

RT-PCR assay demonstrated a high degree of sensitivity for pulmonary TB and good sensitivity for extra-pulmonary TB. It indicated a high degree of specificity for ruling in TB infection from sampling regimes. This was acceptable, but may better as a rule out add-on diagnostic test. RT-PCR assays demonstrate both a high degree of sensitivity in pulmonary samples and rapidity of detection of TB which is an important factor in achieving effective global control and for patient management in terms of initiating early and appropriate anti-tubercular therapy.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42015027534 .

Distribution of Mycobacterium tuberculosis in Korea in the preceding decade

BACKGROUND

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (MTB); it is transmitted among people through air. The aim of this study was to assess the prevalence of TB and its clinical trends by collecting and analyzing data on specimens in Korea.

METHODS

All clinical specimens referred to the Dankook University Hospital Laboratory in Cheonan, Korea, from September 2005 to June 2016 were tested to isolate MTB using solid and liquid cultures, acid-fast bacilli (AFB) smears, and polymerase chain reactions (PCR).

RESULTS

In total, 146 150 specimens were collected; the mean TB positivity rate was 7.8%. The highest positivity rate was observed among patients 30-39 years of age (12.6%), followed by those 20-29 years of age (12.2%). The mean positivity rate was highest in 2010 and lowest in 2016 (10.7% and 6.7%, respectively). When comparing 2015-2011, we saw a decrease in the number of TB-positive patients of 3.4%; this represented an annual decrease in 0.9%.

CONCLUSION

Our data revealed a trend for a decrease in TB prevalence over time. Moreover, TB positivity rates were highest among the younger age groups in our study. Therefore, rapid diagnosis and treatment of TB in younger individuals are crucial.

Clinical evaluation of the Abbott RealTime MTB Assay for direct detection of Mycobacterium tuberculosis-complex from respiratory and non-respiratory samples

Rapid and reliable diagnosis is crucial for correct management of tuberculosis. The Abbott RealTime MTB Assay represents a novel qualitative real-time PCR assay for direct detection of M. tuberculosis-complex (MTB) DNA from respiratory samples. The test targets two highly conserved sequences, the multi-copy insertion element IS6110 and the protein antigen B (PAB) gene of MTB, allowing even the detection of IS6610-deficient strains. We evaluated this commercial diagnostic test by analyzing 200 respiratory and, for the first time, 87 non-respiratory clinical specimens from our tertiary care institution and compared its results to our IS6110-based in-house real-time PCR for MTB as well as MTB culture. Overall sensitivity for Abbott RealTime MTB was 100% (19/19) in smear positive and 87.5% (7/8) in smear negative specimens, while the specificity of the assay was 100% (260/260). For both non-respiratory smear positive and smear negative specimens Abbott RealTime MTB tests showed 100% (8/8) sensitivity and 100% (8/8) specificity. Cycle threshold (Ct) value analysis of 16 MTB positive samples showed a slightly higher Ct value of the Abbott RealTime MTB test compared to our in-house MTB assay (mean delta Ct = 2.55). In conclusion, the performance of the new Abbott RealTime MTB Assay was highly similar to culture and in-house MTB PCR. We document successful analysis of 87 non-respiratory samples with the highly automated Abbott RealTime MTB test with no inhibition observed.

Evaluation of the Abbott RealTime MTB and RealTime MTB INH/RIF Assays for Direct Detection of Mycobacterium tuberculosis Complex and Resistance Markers in Respiratory and Extrapulmonary Specimens

The Abbott RealTime MTB (RT MTB) assay is a new automated nucleic acid amplification test for the detection of Mycobacterium tuberculosis complex (MTBC) in clinical specimens. In combination with the RealTime MTB INH/RIF (RT MTB INH/RIF) resistance assay, which can be applied to RT MTB-positive specimens as an add-on assay, the tests also indicate the genetic markers of resistance to isoniazid (INH) and rifampin (RIF). We aimed to evaluate the diagnostic sensitivity and specificity of RT MTB using different types of respiratory and extrapulmonary specimens and to compare performance characteristics directly with those of the FluoroType MTB assay. The resistance results obtained by RT MTB INH/RIF were compared to those from the GenoType MTBDRplus and from phenotypic drug susceptibility testing. A total of 715 clinical specimens were analyzed. Compared to culture, the overall sensitivity of RT MTB was 92.1%; the sensitivity rates for smear-positive and smear-negative samples were 100% and 76.2%, respectively. The sensitivities of smear-negative specimens were almost identical for respiratory (76.3%) and extrapulmonary (76%) specimens. Specificity rates were 100% and 95.8% for culture-negative specimens and those that grew nontuberculous mycobacteria, respectively. RT MTB INH/RIF was applied to 233 RT MTB-positive samples and identified resistance markers in 7.7% of samples. Agreement with phenotypic and genotypic drug susceptibility testing was 99.5%. In conclusion, RT MTB and RT MTB INH/RIF allow for the rapid and accurate diagnosis of tuberculosis (TB) in different types of specimens and reliably indicate resistance markers. The strengths of this system are the comparably high sensitivity with paucibacillary specimens, its ability to detect INH and RIF resistance, and its high-throughput capacities.

Multicenter Evaluation of Anyplex Plus MTB/NTM MDR-TB Assay for Rapid Detection of Mycobacterium tuberculosis Complex and Multidrug-Resistant Isolates in Pulmonary and Extrapulmonary Specimens

The rapid diagnosis of tuberculosis (TB) and the detection of drug-resistant Mycobacterium tuberculosis strains are critical for successful public health interventions. Therefore, TB diagnosis requires the availability of diagnostic tools that allow the rapid detection of M. tuberculosis and drug resistance in clinical samples. Here, we performed a multicenter study to evaluate the performance of the Seegene Anyplex MTB/NTM MDR-TB assay, a new molecular method based on a multiplex real-time PCR system, for detection of Mycobacterium tuberculosis complex (MTBC), nontuberculous mycobacteria (NTM), and genetic determinants of drug resistance. In total, the results for 755 samples (534 pulmonary and 221 extrapulmonary samples) were compared with the results of smears and cultures. For pulmonary specimens, the sensitivities of the Anyplex assay and acid-fast bacillus smear testing were 86.4% and 75.0%, respectively, and the specificities were 99% and 99.4%. For extrapulmonary specimens, the sensitivities of the Anyplex assay and acid-fast bacillus smear testing were 83.3% and 50.0%, respectively, and the specificities of both were 100%. The negative and positive predictive values of the Anyplex assay for pulmonary specimens were 97% and 100%, respectively, and those for extrapulmonary specimens were 84.6% and 100%. The sensitivities of the Anyplex assay for detecting isoniazid resistance in MTBC strains from pulmonary and extrapulmonary specimens were 83.3% and 50%, respectively, while the specificities were 100% for both specimen types. These results demonstrate that the Anyplex MTB/NTM MDR-TB assay is an efficient and rapid method for the diagnosis of pulmonary and extrapulmonary TB and the detection of isoniazid resistance.

Comparative Study of a Real-Time PCR Assay Targeting senX3-regX3 versus Other Molecular Strategies Commonly Used in the Diagnosis of Tuberculosis

Background

Nucleic acid amplification tests are increasingly used for the rapid diagnosis of tuberculosis. We undertook a comparative study of the efficiency and diagnostic yield of a real-time PCR senX3-regX3 based assay versus the classical IS6110 target and the new commercial methods.

Methods

This single-blind prospective comparative study included 145 consecutive samples: 76 from patients with culture-confirmed tuberculosis (86.8% pulmonary and 13.2% extrapulmonary tuberculosis: 48.7% smear-positive and 51.3% smear-negative) and 69 control samples (24 from patients diagnosed with non-tuberculous mycobacteria infections and 45 from patients with suspected tuberculosis which was eventually ruled out). All samples were tested by two CE-marked assays (Xpert^®MTB/RIF and AnyplexTM plus MTB/NTM) and two in-house assays targeting senX3-regX3 and the IS6110 gene.

Results

The detection limit ranged from 1.00E+01 fg for Anyplex, senX3-regX3 and IS6110 to 1.00E+04 fg for Xpert. All three Xpert, senX3-regX3 and IS6110 assays detected all 37 smear-positive cases. Conversely, Anyplex was positive in 34 (91.9%) smear-positive cases. In patients with smear-negative tuberculosis, differences were observed between the assays; Xpert detected 22 (56.41%) of the 39 smear-negative samples, Anyplex 24 (61.53%), senX3-regX3 28 (71.79%) and IS6110 35 (89.74%). Xpert and senX3-regX3 were negative in all control samples; however, the false positive rate was 8.7% and 13% for Anyplex and IS6110, respectively. The overall sensitivity was 77.6%, 85.7%, 77.3% and 94.7% and the specificity was 100%, 100%, 90.8% and 87.0% for the Xpert, senX3-regX3, Anyplex and IS6110 assays, respectively.

Conclusion

Real-time PCR assays targeting IS6110 lack the desired specificity. The Xpert MTB/RIF and in-house senX3-regX3 assays are both sensitive and specific for the detection of MTBC in both pulmonary and extrapulmonary samples. Therefore, the real time PCR senX3-regX3 based assay could be a useful and complementary tool in the diagnosis of tuberculosis.

Performance evaluation of three commercial molecular assays for the detection of Mycobacterium tuberculosis from clinical specimens in a high TB-HIV-burden setting

BACKGROUND

A major challenge faced by countries with a high burden of tuberculosis (TB) is early detection especially in individuals with paucibacillary disease which is common in HIV endemic settings. Remarkable efforts have been made globally to accelerate the development and expansion of new diagnostic technologies that allow better and earlier diagnosis of active tuberculosis particularly directly from clinical specimens with a few commercial options available. These include GenoType MTBDRplus Version 2.0 (Hain Lifescience), Xpert® MTB/RIF (Cepheid) and Anyplex™ plus MTB/NTM/DR-TB Real-time detection (Seegene). We evaluated the diagnostic performance of these three commercial molecular assays for the detection of Mycobacterium tuberculosis complex from clinical specimens in a high TB-HIV-burden setting.

METHODS

This was a retrospective laboratory-based study using stored remnant sediments from clinical specimens of presumptive pulmonary TB cases. A stratified sample of smear positive TB, smear negative TB and TB culture negatives was included. All the samples were tested on the three molecular assays following the manufacturers' instructions; except for Anyplex™plus, for which DNA extraction was performed using the NucliSENS® easyMAG® platform (bioMerieux). Samples were also processed for liquid TB culture and time-to-culture positivity was recorded.

RESULTS

Of the 90 sediments processed, 81 were analyzable across all three systems. The overall sensitivity was highest for Xpert® MTB/RIF (89.1%) followed by GenoType MTBDRplus (70.9%) and Anyplex™ plus (65.5%). The specificity and sensitivity in smear positive cases was comparable across all systems. There was a significant difference in sensitivity between Xpert® MTB/RIF and the other two assays for smear-negative cases (P < 0.05). The performance in cases where the time-to-culture positivity was ≥ 20 days was also significantly poorer for both Anyplex™ plus and GenoType MTBDRplus compared to Xpert® MTB/RIF (P < 0.05). Xpert® MTB/RIF achieved 100% specificity, while Anyplex™ plus and GenoType MTBDRplus achieved 96.2 and 92.3% respectively.

CONCLUSION

The Xpert® MTB/RIF was superior to the other two assays for the detection of TB in smear negative specimens notably when bacterial loads are very low in sputum. It is important that studies reporting on test performance stratify their results by time-to-culture positivity to accurately assess clinical performance especially in high HIV settings.

Simple Detection of the IS6110 Sequence of Mycobacterium tuberculosis Complex in Sputum, Based on PCR with Graphene Oxide

Graphene oxide (GO) has proven to be a satisfactory DNA-sensor platform for applications in enzyme-free signal amplification, fluorescence-based amplification, and nanoparticle-based platforms because of its excellent electrical, thermal, and optical properties. In this study, we designed a novel platform for the fluorescence detection of biomolecules, using a fluorescent dye-labeled primer and GO. We applied this system for the detection of the IS6110 insertion sequence of the Mycobacterium tuberculosis complex (MTB) and evaluated its feasibility for use in molecular diagnostics. Fifty-four sputum specimens were collected at our institution from October 2010 to March 2012. To detect MTB in the samples, we performed PCR amplification of the IS6110 DNA sequence using FAM-labeled primers, after which the PCR amplicon was incubated with GO and the fluorescence was measured. The results were compared with those obtained by conventional real-time quantitative PCR (RQ-PCR). The fluorescence intensity observed increased in a concentration-dependent manner with the FAM-labeled IS6110 amplicon. The results of the PCR-GO system for detecting IS6110 DNA were in good agreement with those obtained with conventional RQ-PCR (kappa statistic = 0.925). The PCR-GO system detected MTB DNA in 23 of 25 RQ-PCR-positive sputum samples (92.0%; 95% CI, 75.0–98.0%), but not in 29 of 29 RQ-PCR-negative sputum samples (100%; 95% CI, 88.1–100.0%). These results indicate the utility of the PCR-GO system in molecular diagnostics.

Performance of the new automated Abbott RealTime MTB assay for rapid detection of Mycobacterium tuberculosis complex in respiratory specimens

The automated high-throughput Abbott RealTime MTB real-time PCR assay has been recently launched for Mycobacterium tuberculosis complex (MTBC) clinical diagnosis. This study would like to evaluate its performance. We first compared its diagnostic performance with the Roche Cobas TaqMan MTB assay on 214 clinical respiratory specimens. Prospective analysis of a total 520 specimens was then performed to further evaluate the Abbott assay. The Abbott assay showed a lower limit of detection at 22.5 AFB/ml, which was more sensitive than the Cobas assay (167.5 AFB/ml). The two assays demonstrated a significant difference in diagnostic performance (McNemar's test; P = 0.0034), in which the Abbott assay presented significantly higher area under curve (AUC) than the Cobas assay (1.000 vs 0.880; P = 0.0002). The Abbott assay demonstrated extremely low PCR inhibition on clinical respiratory specimens. The automated Abbott assay required only very short manual handling time (0.5 h), which could help to improve the laboratory management. In the prospective analysis, the overall estimates for sensitivity and specificity of the Abbott assay were both 100 % among smear-positive specimens, whereas the smear-negative specimens were 96.7 and 96.1 %, respectively. No cross-reactivity with non-tuberculosis mycobacterial species was observed. The superiority in sensitivity of the Abbott assay for detecting MTBC in smear-negative specimens could further minimize the risk in MTBC false-negative detection. The new Abbott RealTime MTB assay has good diagnostic performance which can be a useful diagnostic tool for rapid MTBC detection in clinical laboratories.

Comparison of the genedia MTB detection kit and the cobas TaqMan MTB assay for detection of Mycobacterium tuberculosis in respiratory specimens

The performance of the Genedia MTB detection kit was compared with that of the Cobas TaqMan MTB test using respiratory specimens. The Genedia and Cobas assays showed comparable sensitivities (81.8% and 78.8%, respectively) and specificities (99.8% and 99.5%, respectively), while the Genedia assay produced fewer invalid results and required less turnaround time and labor.

Evaluation of the Cobas TaqMan MTB test for the detection of Mycobacterium tuberculosis complex according to acid-fast-bacillus smear grades in respiratory specimens

We evaluated the performance of the Cobas TaqMan MTB test (Roche Diagnostics, Basel, Switzerland), stratified by acid-fast bacilli (AFB) smear grades. The sensitivity of this test in smear-positive specimens was >95% in all grades, while that in trace and negative specimens was 85.3% and 34.4%, respectively.