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Original Research: Chest Infections |

Rapid Detection of Mycobacterium tuberculosis Using a Novel Ultrafast Chip-Type Real-Time Polymerase Chain Reaction SystemRapid Detection of Mycobacterium Tuberculosis FREE TO VIEW

Seung Hyeun Lee, MD, PhD; Sung-Woo Kim, PhD; Sehyun Lee, MSc; EunSub Kim, MSc; Duck-Joong Kim, MSc; Sohyun Park, MSc; Eun Joo Lee, MD, PhD; Sang Yeub Lee, MD, PhD; Ji Sung Lee, PhD; Chae Seung Lim, MD, PhD; Won-Ki Kim, PhD; Kwang Ho In, MD, PhD
Author and Funding Information

From the Division of Respiratory and Critical Care Medicine (Dr S. H. Lee), Department of Internal Medicine, KEPCO Medical Center; NanoBioSys Inc (Dr S.-W. Kim, Mss S. Lee and Park, and Messrs E. Kim and D.-J. Kim); Division of Respiratory and Critical Care Medicine, Department of Internal Medicine (Drs E. J. Lee, S. Y. Lee, and In), Department of Laboratory Medicine (Dr Lim), and Department of Neuroscience (Dr W.-K. Kim), College of Medicine, Korea University; and Biostatistical Consulting Unit (Dr J. S. Lee), Sunchunhyang University Medical Center, Seoul, South Korea.

CORRESPONDENCE TO: Kwang Ho In, MD, PhD, Division of Respiratory and Critical Care Medicine, Department of Internal Medicine, College of Medicine, Korea University, 126-1, Anam-dong 5-ga, Seongbuk-gu, Seoul 136-705, South Korea; e-mail: khin@kumc.or.kr


Drs S. H. Lee and S.-W. Kim contributed equally.

FUNDING/SUPPORT: This study was supported by a grant from the Industrial Source Technology Development Program [No. 2010-10038674] of the Ministry of Knowledge Economy of the Korean government.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;146(5):1319-1326. doi:10.1378/chest.14-0626
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BACKGROUND:  NBS LabChip G2-3 is a novel, ultrafast, chip-type portable real-time polymerase chain reaction (PCR) system. We evaluated the clinical usefulness of this system in detecting pulmonary TB and assessed its diagnostic performance compared with a conventional tube-type PCR system.

METHODS:  A total of 247 sputum samples were collected from patients suspected of having pulmonary TB. After the decontamination process, these samples were examined by fluorescence staining for acid-fast bacilli, cultures with both solid and liquid media, and real-time PCR with the NBS LabChip and a conventional tube-type system. The diagnostic accuracy of the NBS LabChip system and the agreement between the two assays were evaluated.

RESULTS:  Considering mycobacterial culture results as a gold standard, the overall sensitivity and specificity of the NBS LabChip was 83.8% (95% CI, 73.8%-91.1%) and 94.0% (95% CI, 89.3%-97.1%), respectively. For the detection of TB from the smear-positive samples, the sensitivity and specificity of the NBS LabChip was 96.0% (95% CI, 86.3%-99.5%) and 83.3% (95% CI, 72.3%-95.7%), respectively. For the smear-negative samples, the sensitivity and specificity of the NBS LabChip was 63.3% (95% CI, 43.9%-80.1%) and 95.0% (95% CI, 90.4%-97.8%), respectively. There were no significant differences in the sensitivity and specificity between the NBS LabChip and a conventional tube-type system, although the NBS LabChip shortened the PCR time (27 min for 45 cycles).

CONCLUSIONS:  The NBS LabChip G2-3 system has potential as an ultrafast, cost-effective diagnostic tool for pulmonary TB with high sensitivity and specificity.

Figures in this Article

TB is one of the major public health problems worldwide despite substantial efforts to control the disease. According to a 2013 World Health Organization report, 8.7 million new cases of active TB and 1.4 million deaths occur annually.1 The prevalence of TB in Korea is much higher compared with western countries; its incidence has been reported to be 100 per 100,000 individuals, and multidrug-resistant TB accounts for 4.6% of all cases.2,3 Prompt and exact diagnosis of TB is essential for treating the disease and preventing transmission.4 This is the reason for active efforts to develop rapid and sensitive techniques for the diagnosis of TB.

Polymerase chain reaction (PCR) is the most common methodology to rapidly detect Mycobacterium tuberculosis (MTB) by amplification of its specific DNA sequence. It has improved the accuracy and reduced the time for the diagnosis of TB because it can detect MTB even in paucibacillary samples using specific primers. Real-time PCR amplifies and quantifies a target DNA molecule simultaneously, and several automated real-time PCR systems are now commercially available and widely used in hospital laboratories of industrialized countries.5

The Ultrafast NBS LabChip G2-3 system (NanoBioSys) is a novel chip-based portable real-time PCR system. It uses a microfluidic chip-based technique in contrast to the tube-based approach used by most other real-time PCR systems. It is characterized by a markedly shortened PCR time and minimal system size. This system showed high sensitivity and specificity in the diagnosis of 2009 influenza A(H1N1), with a total reaction time of 15 min to perform 30 cycles.6 However, to our knowledge no study has validated its diagnostic accuracy in patients who are suspected of having TB. The aim of the present study was to establish the analytic performance and clinical usefulness of this novel chip-based real-time PCR system in detecting pulmonary TB and to assess its diagnostic accuracy compared with a conventional tube-type PCR system.

Study Design

To evaluate the analytic performance of the new system prior to clinical validation, cycle threshold (Ct) value, analytic sensitivity, and analytic specificity for the NBS LabChip system were tested. To determine optimal Ct value, we performed receiver operating characteristic curve analysis for various Ct values ranging from 30 to 45 by using 61 genomic DNA (gDNA) samples of MTB and 148 MTB-negative samples. Analytic sensitivity of the assay was tested by using serial 10-fold dilutions of gDNA of MTB (from 1 × 107 to 1 × 100 copies) in duplicate. Analytic specificity was evaluated by using gDNA (1 × 107 copies) of MTB and 11 nontuberculous mycobacterium (NTM) species (Mycobacteriumavium, Mycobacterium intracellulare, Mycobacterium fortuitum, Mycobacterium gordonae, Mycobacterium abscessus, Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium celatum, Mycobacterium chelonae, Mycobacterium mucogenicum, and Mycobacterium xenopi) and three bacterial species (Streptococcus pneumonia, Haemophilus influenzae, and Mycoplasma pneumoniae). Mycobacterial and bacterial samples were donated from the Korean Institute of Tuberculosis and Korean Centers for Disease Control, respectively. To confirm the successful amplification, PCR amplicons underwent 2% agarose gel electrophoresis.

For clinical validation of the assay, 247 sputum samples were prospectively collected from patients suspected of having pulmonary TB at Korea University Hospital, a tertiary-care hospital in Seoul, South Korea, between March 2012 and November 2013. Clinical data, including radiologic and laboratory findings, were collected through an electronic chart review. All clinical samples were examined by fluorescence staining for acid-fast bacilli (AFB), culture with both solid and liquid media, and the real-time PCR with the NBS LabChip and a conventional tube-type system. The study protocol was reviewed and approved by the Clinical Research Ethics Committee of the Korea University Medical Center (ED11072). Written informed consent was obtained from all patients.

Sample Processing

Before the diagnostic procedures, sputum samples were decontaminated. Each sample received a maximum of twice the volume of 2% N-acetyl-l-cysteine and sodium hydroxide, was mixed by vortexing for 20 s, and was centrifuged at 3,000g for 20 min. The resuspended sediment was used for AFB smear staining and culture. For the sediment to undergo PCR, the gDNA was isolated by using QIAamp DNA Mini Kit (QIAGEN) according to the manufacturer’s instructions.

AFB smear of decontaminated sputum was performed with auramine-rhodamine fluorescence staining followed by confirmation with Ziehl-Neelsen staining. Samples with grades 1 to 4 were defined as smear positive according to Centers for Disease Control and Prevention recommendations. Mycobacterial cultures were prepared by inoculation with 500 μL aliquots of the decontaminated samples into a Löwenstein-Jensen medium and BACTEC MGIT 960 Mycobacterial Detection System (BD Diagnostic Systems) for solid and liquid cultures, respectively. Both media for mycobacterial culture were incubated at 37°C for up to 8 weeks until growth was observed. Positive cultures were subjected to AFB staining to confirm the presence of AFB and to exclude contamination. In addition, positive cultures in liquid media were confirmed by both the presence of cord formation and a test using TB MPT64 antigen (Standard Diagnostics Inc). A sample was determined to be culture positive if any of the two culture media yielded a positive result.

Real-Time PCR Using NBS LabChip

Expectorated sputum samples were decontaminated and gDNA isolated. After mixing the gDNA with PCR master mix, 12 μL of the mixture was inoculated on the chip. The chip in a case was inserted into the machine, and ultrafast real-time PCR was conducted within 27 min for 45 cycles. The detailed procedures and the primers and probe used in the assay are provided in e-Appendix 1.

Conventional Real-Time PCR

For conventional tube-type PCR, we used the CFX96 Touch thermocycler (Bio-Rad Laboratories, Inc). A 50% (volume/volume [v/v]) real-time PCR master mix, 5% to 10% (v/v) gDNA, and 10% (v/v) TB primers and probe mixture were added to generate a 20-μL reaction mixture. Real-time PCR was carried out with a preincubation at 42°C for 300 s, predenaturation at 95°C for 10 s, and then 45 cycles at 95°C for 10 s and 64°C for 30 s. It usually took 86 min for 45 cycles of real-time PCR with this system. No template control (NTC) was used to monitor contamination of PCR reagents. A sample with a Ct value < 45 was considered positive when the Ct value of the NTC was not apparent.

Statistical Analyses

We defined positive mycobacterial culture results as a gold standard of the diagnosis. On the basis of culture results, we calculated the sensitivity, specificity, positive predictive value, and negative predictive value with 95% CIs of the two PCR systems for the detection of MTB. We compared the sensitivity and specificity between the two assays by using exact McNemar test. The agreement between the two assays was further assessed by κ statistics with 95% CIs. P < .05 (two-tailed test) was considered statistically significant. Statistical analysis was performed with SAS 9.3 (SAS Institute Inc) software.

Analytic Performance of NBS LabChip

Receiver operating characteristic curve analysis results for the determination of the optimal Ct value for this new system are shown in Figure 1. As Ct values increased from 30 to 40, the sensitivity for each Ct value increased from 32.8% to 95.08%. Sensitivity did not increase further when the Ct value exceeded 41. Specificity was maintained as 100% for all Ct values. At a Ct value of 40, the best area under the curve was obtained (0.975; 95% CI, 0.964-0.992), with a sensitivity of 95.08% and a specificity of 100%. Thus, a sample with a Ct value < 40 was considered positive when the Ct value of the NTC was not apparent.

Figure Jump LinkFigure 1 –  Determination of the optimal cycle threshold (Ct) value for the NBS LabChip system. Dots along the receiver operating characteristic curves indicate sensitivities for various Ct values ranging from 30 to 45. Ct value 40 was determined as the cutoff based on the AUC for the detection of Mycobacterium tuberculosis. AUC = area under the curve.Grahic Jump Location

Results of analytic sensitivities of the two PCR systems are shown in Figure 2. The NBS LabChip system could detect one copy of gDNA with good reproducibility, which was identical to the tube-type PCR system. Gel electrophoresis revealed a band at 183 base pair, as expected, and confirmed the successful amplification of the serially diluted gDNAs. In addition, the standard curves showed a log-linear relationship between Ct value and gDNA copy numbers over the entire dynamic range. These findings indicated that real-time PCR in the NBS LabChip system was as efficient as a conventional tube-type system and that the assay provides a semiquantitative estimation of the gDNA copy number of the sample.

Figure Jump LinkFigure 2 –  Comparison of analytic sensitivities for the two real-time polymerase chain reaction (PCR) systems. A, Amplification curves and standard plots for a tube-type real-time PCR system (CFX96; Bio-Rad Laboratories, Inc) and the NBS LabChip system (NanoBioSys Inc) by using 10-fold dilutions of genomic DNA of MTB. B, The Ct values for each copy number were identical in both systems. C, Gel electrophoresis for PCR amplicons showed a band at 183 base pair (arrow) and confirms the successful amplification. M = 100-base pair DNA marker; MTB = Mycobacterium tuberculosis; NTC = no template control. See Figure 1 legend for expansion of other abbreviations.Grahic Jump Location

In the evaluation for analytic specificity, none of the 11 NTM and three bacterial species tested was falsely amplified by the NBS LabChip system. This finding suggests a high specificity of the primers and probe used in the system.

Performance of Each Detection Method

Table 1 summarizes the results of each detection method. From the 247 samples, 80 (32.4%) were MTB culture positive and 160 (64.8%) were culture negative. Seven (2.8%) were NTM culture positive: M avium (n = 4), M intracellulare (n = 2), and M abscessus (n = 1). Among the 80 samples that were MTB culture positive, 50 (62.5%) were smear positive and 30 (37.5%) smear negative. Among seven samples that were NTM culture positive, six (85.7%) were smear positive and one (14.3%) smear negative. All samples that were MTB culture negative were smear negative. Thus, the sensitivity and specificity of AFB smear for MTB were 62.5% (95% CI, 51.0%-73.1%) and 96.4% (95% CI, 92.3%-98.7%), respectively.

Table Graphic Jump Location
TABLE 1 ]  Performance of CFX96 and NBS LabChip Assay Based On Mycobacterial Culture Results

P values by exact McNemar test. MTB = Mycobacterium tuberculosis; NPV = negative predictive value; NTM = nontuberculous mycobacterium; PCR = polymerase chain reaction; PPV = positive predictive value.

Among 50 samples that were smear positive and MTB culture positive, NBS LabChip showed positive results in 48 (96.0%), whereas CFX96 was positive in 49 (98.0%). Among 30 samples that were smear negative and MTB culture positive, NBS LabChip detected TB in 19 (63.3%), whereas CFX96 detected TB in 21 (70.0%). Among 160 culture-negative samples, NBS LabChip was negative in 152 (95.0%) and positive in eight (5.0%), whereas CFX96 was negative in 150 (93.8%) and positive in 10 (6.2%). Of seven samples that were NTM culture positive, one was PCR positive in both systems. Considering the mycobacterial culture results as the gold standard for the detection of MTB in smear-positive samples, the sensitivity and specificity of the NBS LabChip assay was 96.0% (95% CI, 86.3%-99.5%) and 83.3% (95% CI, 72.3%-95.7%), respectively. For the smear-negative samples, the sensitivity and specificity of the system was 63.3% (95% CI, 43.9%-80.1%) and 95.0% (95% CI, 90.4%-97.8%), respectively. The overall sensitivity and specificity for the diagnosis of MTB was 83.8% (95% CI, 73.8%-91.1%) and 94.0% (95% CI, 89.3%-97.1%), respectively. The new system showed significantly higher sensitivity compared with AFB smear (83.8% vs 62.5%, P = .0002). In addition, the NBS LabChip system showed no significant difference for the sensitivity and specificity compared with those of the CFX96 thermocycler, regardless of the smear results (Table 1).

Agreement Analysis

Table 2 summarizes the agreement analysis between results from the CFX96 thermocycler and the NBS LabChip assay. Of the 247 samples, 77 and 170 showed positive and negative results on the NBS LapChip, respectively. In contrast, 82 and 165 showed positive and negative results on the CFX96, respectively. There was an agreement in 238 of the 247 samples between the two assays. Of the nine mismatched samples, seven were positive on the CFX96 but negative on the NBS LabChip; these seven samples comprised three culture-positive cases and four culture-negative cases. In addition, two samples were positive on the NBS LabChip but negative on the CFX96, both of which were culture-negative cases. On weighted κ analysis, the κ values ranged from 0.65 to 0.85, indicating substantial to high agreement between the two assays (Table 2).

Table Graphic Jump Location
TABLE 2 ]  Agreement Between Results From CFX96 and NBS LabChip Assays

In the present study, the NBS LabChip G2-3 system detected MTB in sputum samples with high sensitivity and specificity. Moreover, no significant difference was found in the diagnostic performance between the new system and a conventional tube-type PCR system, although the new system dramatically shortened the PCR time (27 min vs 86 min). To our knowledge, this study is the first to validate the performance of a chip-type real-time PCR system compared with that of a conventional tube-type PCR for the diagnosis of pulmonary TB.

Traditionally, AFB direct smear and TB culture has been the bedrock of TB diagnosis in laboratories. Although the direct AFB smear is cost-effective, it suffers from low sensitivity and specificity.7 Mycobacterial culture is a gold standard for the diagnosis of TB, but it takes at least 2 weeks, even with the recently introduced liquid culture system.8 Over the past decade, rapid techniques to detect MTB, such as imaging with fluorescence microscopy, liquid culture system, and line probe assay, have been introduced into clinical practice. These innovations have aided early diagnosis and proper treatment.5 PCR is a rapid and safe diagnostic modality that can detect specific nucleotide sequences of the pathogen with a sensitivity that is much higher than that of smear microscopy.7,9 Several rapid real-time PCR systems enable detection of TB within hours and are popular in clinical practice. The Xpert MTB/RIF (Cepheid), a fully automated real-time PCR system, has shown high sensitivity in detecting both MTB and rifampin-resistant TB within 2 h.10 On the basis of these data, the World Health Organization formally endorsed the use of the assay in 2010.

The overall sensitivity and specificity of commercially available real-time PCR systems range between 75.0% and 98.0% and between 85.1% and 99.3%, respectively.5,1014 In addition, the sensitivity for smear-negative samples is reported to be 50.0% to 70.8%, whereas that for smear-positive samples is 87.5% to 100%.15 Presently, the NBS LabChip system demonstrates similar sensitivity and specificity compared with previously validated conventional tube-type PCR systems regardless of smear results, even with its short PCR time (27 min for 45 cycles) and its small size (5.5 kg). To be fast and cost-effective, the system uses microfluidic chip-based analysis and is equipped with a rapid thermocycler along with an advanced fluorescence detection method.6 Interest in chip-based real-time PCR has been growing because it requires only a small reaction volume in microfluidic channels (12 μL in this system), which enables rapid temperature control, minimizing the total reaction time and system volume.16,17 Moreover, this system uses a novel heat-transferable, light-transparent, and disposable polycarbonate chip with large surface-to-volume ratio in the microchannels.6 Compared with previously described glass or silicone chips, the NBS chip is light, low-cost, and easy to handle.6 The raw material cost of the plastic chip (0.2-2 cents/cm2) is much more inexpensive than other types of chips, such as glass (5-40 cents/cm2) and silicon (12-16 cents/cm2) wafers.6 In addition, conventional glass and silicon chips require a complex, multistep, and expensive fabrication process for the generation of microchannels and reaction chambers.18 By using the polymeric chip, we could simplify the process by adopting a one-step injection molding method to generate its multilayer structure, which reduces the cost of fabrication. This has enabled us to reduce the total cost per test (about $8-$10) compared with previous PCR systems.

In this study, nine samples were identified as false positive in the new real-time PCR system. Of these samples, eight were smear and culture negative, and one was NTM culture positive. Medical review revealed that the eight samples were collected from the patients with an old TB scar on chest radiography or previous history of pulmonary TB without evidence of active pulmonary TB. Therefore, these samples could have resulted from the amplification of gDNA of dormant TB bacilli. The other sample displayed cross-reactivity in NTM and was identified as M avium. One sample was false positive in both PCR systems. Because this result may indicate mixed NTM/TB culture, we performed a second culture for this sample. However, only NTM (M avium) was detected, suggesting true false positivity in both PCR systems. Thirteen samples were identified as false negative on the NBS LabChip assay. False-negative results in PCR might be due to low AFB load, presence of the amplification inhibitor, or heterogeneous distribution of DNA in the samples.19 Of the 13 false-negative results, 11 were smear negative, and all exhibited a positive result after 4 weeks of incubation in liquid culture. Thus, these false-negative results could have been attributable to low AFB load. False negative findings in some samples may be attributable to small test volume for real-time PCR compared with culture.20 For solid and liquid culture, 500-μL aliquots were inoculated into each culture media. This volume is > 40 times the amount applied on the chip for the NBS LabChip assay. These results demonstrate that mycobacterial culture is still superior compared with PCR in the diagnosis of MTB, especially in cases of low AFB load.

Although several chip-based real-time PCR assays have been shown to reduce reaction cost and time and system size, none were proven to have clinical usefulness comparable with that of conventional real-time PCR systems. We have demonstrated the diagnostic performance of a novel chip-type real-time PCR system for MTB with considerable sensitivity and specificity. However, there are several limitations in this study. First, we did not evaluate the performance of the system to discriminate drug-resistant MTB strains simultaneously. Investigation for evaluating the usefulness of this system by using a specific primer to that end has just been undertaken. Second, the nucleic acid extraction step still limited the total turnaround time of this new system. An automated system that integrates the DNA extraction procedure would reduce the total time to results and the risk of contamination or loss of DNA by minimizing hands-on time. Very recently, an automated DNA extraction platform has been developed by the same company. A fully automated system combining this platform with the NBS LabChip system could provide a potential point-of-care diagnostic modality in clinical practice.

In conclusion, this study demonstrates that the NBS LabChip real-time PCR system has potential as an ultrafast, cost-effective diagnostic tool for pulmonary TB with high sensitivity and specificity. Additionally, the present results suggest a new paradigm for rapid molecular diagnosis of many diseases and provide evidence for the use of chip-based nucleic acid amplification techniques in clinical practice. Further investigation for other pathogens, either virus or bacteria, and for various specimens other than sputum will expand the clinical use of this novel system.

Author contributions: K. H. I. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. S. H. L., S.-W. K., and W.-K. K. contributed to the organization and performance of the investigation, quality control, data analysis and interpretation, and drafting of the manuscript; S. L., E. K., D.-J. K., and S. P. contributed to the performance of the investigation, data collection, and manuscript preparation; E. J. L., S. Y. L., and C. S. L. contributed to the data analysis and interpretation and review and approval of the final manuscript; J. S. L. contributed to the study design, statistical review, and writing of the manuscript; and K. H. I. contributed to study conception and design, data analysis and interpretation, drafting of the manuscript for important intellectual content, and review and approval of the final manuscript.

Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr S.-W. Kim, Mss S. Lee and Park, and Messrs E. Kim and D.-J. Kim are employed by NanoBioSys Inc and participated in this work as coworkers. The other authors have no involvement with NanoBioSys Inc, concerning employment, consultancy, patents, and products in development or marketed products. The test chips and other materials for the test were provided by the company free of cost. Drs S. H. Lee, E. J. Lee, S. Y. Lee, J. S. Lee, Lim, W.-K. Kim, and In have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Role of sponsors: The sponsors had no role in the design of the study, the collection and analysis of the data, or the preparation of the manuscript.

Additional information: The e-Appendix can be found in the Supplemental Materials section of the online article.

AFB

acid-fast bacilli

Ct

cycle threshold

gDNA

genomic DNA

MTB

Mycobacterium tuberculosis

NTC

no template control

NTM

nontuberculous mycobacterium

PCR

polymerase chain reaction

v/v

volume/volume

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Figures

Figure Jump LinkFigure 1 –  Determination of the optimal cycle threshold (Ct) value for the NBS LabChip system. Dots along the receiver operating characteristic curves indicate sensitivities for various Ct values ranging from 30 to 45. Ct value 40 was determined as the cutoff based on the AUC for the detection of Mycobacterium tuberculosis. AUC = area under the curve.Grahic Jump Location
Figure Jump LinkFigure 2 –  Comparison of analytic sensitivities for the two real-time polymerase chain reaction (PCR) systems. A, Amplification curves and standard plots for a tube-type real-time PCR system (CFX96; Bio-Rad Laboratories, Inc) and the NBS LabChip system (NanoBioSys Inc) by using 10-fold dilutions of genomic DNA of MTB. B, The Ct values for each copy number were identical in both systems. C, Gel electrophoresis for PCR amplicons showed a band at 183 base pair (arrow) and confirms the successful amplification. M = 100-base pair DNA marker; MTB = Mycobacterium tuberculosis; NTC = no template control. See Figure 1 legend for expansion of other abbreviations.Grahic Jump Location

Tables

Table Graphic Jump Location
TABLE 1 ]  Performance of CFX96 and NBS LabChip Assay Based On Mycobacterial Culture Results

P values by exact McNemar test. MTB = Mycobacterium tuberculosis; NPV = negative predictive value; NTM = nontuberculous mycobacterium; PCR = polymerase chain reaction; PPV = positive predictive value.

Table Graphic Jump Location
TABLE 2 ]  Agreement Between Results From CFX96 and NBS LabChip Assays

References

Global tuberculosis report 2013. World Health Organization website. http://www.who.int/tb/publications/global_report/en/. Accessed January 10, 2014.
 
Park JS. Recent advances in tuberculosis and nontuberculous mycobacteria lung disease. Tuberc Respir Dis (Seoul). 2013;74(6):251-255. [CrossRef] [PubMed]
 
Park YS, Hong SJ, Boo YK, et al. The national status of tuberculosis using nationwide medical records survey of patients with tuberculosis in Korea. Tuberc Respir Dis (Seoul). 2012;73(1):48-55. [CrossRef] [PubMed]
 
Farmer P, Bayona J, Becerra M, et al. The dilemma of MDR-TB in the global era. Int J Tuberc Lung Dis. 1998;2(11):869-876. [PubMed]
 
Drobniewski F, Nikolayevskyy V, Maxeiner H, et al. Rapid diagnostics of tuberculosis and drug resistance in the industrialized world: clinical and public health benefits and barriers to implementation. BMC Med. 2013;11:190. [CrossRef] [PubMed]
 
Song HO, Kim JH, Ryu HS, et al. Polymeric LabChip real-time PCR as a point-of-care-potential diagnostic tool for rapid detection of influenza A/H1N1 virus in human clinical specimens. PLoS One. 2012;7(12):e53325. [CrossRef] [PubMed]
 
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