Evaluation of Xpert MTB/RIF Versus AFB Smear and Culture to Identify Pulmonary Tuberculosis in Patients With Suspected Tuberculosis From Low and Higher Prevalence Settings

Factors associated with tuberculosis treatment initiation among bacteriologically negative individuals evaluated for tuberculosis: an individual patient data meta-analysis

Background

Globally, over one-third of pulmonary tuberculosis (TB) disease diagnoses are made based on clinical criteria after a negative diagnostic test result. Understanding factors associated with clinicians' decisions to initiate treatment for individuals with negative test results is critical for predicting the potential impact of new diagnostics.

Methods

We performed a systematic review and individual patient data meta-analysis using studies conducted between January/2010 and December/2022 (PROSPERO: CRD42022287613). We included trials or cohort studies that enrolled individuals evaluated for TB in routine settings. In these studies participants were evaluated based on clinical examination and routinely-used diagnostics, and were followed for ≥1 week after the initial test result. We used hierarchical Bayesian logistic regression to identify factors associated with treatment initiation following a negative result on an initial bacteriological test (e.g., sputum smear microscopy, Xpert MTB/RIF).

Findings

Multiple factors were positively associated with treatment initiation: male sex [adjusted Odds Ratio (aOR) 1.61 (1.31-1.95)], history of prior TB [aOR 1.36 (1.06-1.73)], reported cough [aOR 4.62 (3.42-6.27)], reported night sweats [aOR 1.50 (1.21-1.90)], and having HIV infection but not on ART [aOR 1.68 (1.23-2.32)]. Treatment initiation was substantially less likely for individuals testing negative with Xpert [aOR 0.77 (0.62-0.96)] compared to smear microscopy and declined in more recent years.

Interpretation

Multiple factors influenced decisions to initiate TB treatment despite negative test results. Clinicians were substantially less likely to treat in the absence of a positive test result when using more sensitive, PCR-based diagnostics.

Sternal Puncture-Induced Acute Spinal Cord Syndrome in a Myeloma-Remissive Patient Revealing Pott Disease: A Case Report

Cord compression is not a known complication of sternal puncture. We report the case of a patient with a history of multiple myeloma who presented acute onset paraplegia brought on during sternal puncture. Neuroimaging revealed focal spondylodiscitis and cord compression by an abscess. Neurosurgical decompression was not carried out on the patient because of her fragile general state of health and tardy consultation. Workup revealed the patient in remission from her multiple myeloma thus making decompressive radiotherapy unnecessary. The diagnosis of Pott disease was made by taking into account the clinical presentation, spine imaging and extra neurological imaging findings. Empiric anti-tuberculosis treatment was initiated which resulted in spectacular outcomes with a patient being able to walk with little aid by the end of her nine-month treatment course.

One- versus two-specimen Xpert strategy to discontinue airborne isolation in suspected pulmonary tuberculosis: systematic review and meta-analysis

BACKGROUND

Evaluation of a patient with suspected pulmonary tuberculosis (TB) involves initiation of airborne infection isolation (AII). However, guidelines detailing discontinuation of AII utilizing the Xpert MTB/RIF provide little clarity between use of one-specimen (1-Xpert') versus two-specimens (2-Xpert').

OBJECTIVES

To evaluate the diagnostic accuracy of one-Xpert versus two-Xpert strategy in guiding discontinuation of AII.

METHODS

Data sources: PubMed, Embase, and EBSCO databases.

STUDY ELIGIBILITY CRITERIA

Studies providing diagnostic accuracy data for one- versus two-Xperts in discontinuation of AII.

PARTICIPANTS

Adult patients with suspected TB.

TESTS

Xpert MTB/RIF on one- versus two-sputum specimens. Reference standard: Solid and liquid culture media. Assessment of risk of bias: Quality Assessment of Diagnostic Accuracy Studies tool was used. Methods of data synthesis: Meta-analysis was performed to calculate the pooled sensitivities and specificities using Stata 17.2.

RESULTS

Four studies were included involving 1776 patients. A total of 68% were males, 36% were HIV positive, and 80% participants belonged to the United States. In patients with suspected pulmonary TB, 7% (95% CI, 6-9%) participants were found to have culture-positive MTB. For one-Xpert strategy, the pooled sensitivity was 86% (95% CI, 75-92%; I2, 1.05%) and specificity was 100% (95% CI, 99-100%; I2, 36%). Two-Xpert strategy had a pooled sensitivity of 92% (95% CI, 84-96%; I2, 16%) and a specificity of 100% (95% CI, 98-100%; I2, 27%). There was statistically significant difference between sensitivities of one-Xpert and two-Xpert strategies (p 0.05) with no statistically significant difference in their specificities.

DISCUSSION

The results of this review must be interpreted in the context of a predominantly low-TB prevalence setting. Two-Xpert strategy has an incrementally higher sensitivity when compared with one-Xpert strategy with similar specificities between the two. Obtaining a second Xpert is crucial for individuals with a continued high suspicion for TB or those at a high risk of morbidity/mortality from TB.

The Role of GeneXpert® for Tuberculosis Diagnostics in Brazil: An Examination from a Historical and Epidemiological Perspective

The rapid molecular test (RMT) performed on the GeneXpert® system is widely used as a control strategy and surveillance technique for tuberculosis (TB). In the region of the Americas, TB incidence is slowly increasing owing to an upward trend in Brazil, which is among the high TB-burden countries (HBCs), ranking in the 19th position. In this context, we aimed to (i) describe the implementation and history of RMT-TB (Xpert® MTB/RIF and Xpert® MTB/RIF Ultra) in Brazil; (ii) to evaluate the national RMT laboratory distribution, TB, and resistance to RIF detection by RMT; and (iii) to correlate these data with Brazilian TB incidence. The quantitative data of Xpert® MTB/RIF and Xpert® MTB/RIF Ultra assays performed in the pulmonary TB investigation from 2014 to 2020 were provided by the Brazilian Ministry of Health. A spatial visualization using ArcGIS software was performed. The Southeast region constituted about half of the RMT laboratories-from 39.4% to 45.9% of the total value over the five regions. Regarding the federal units, the São Paulo state alone represented from 20.2% to 34.1% (5.0 to 8.5 times the value) of RMT laboratories over the years observed. There were significant differences (p < 0.0001) in the frequency of RMT laboratories between all years of the historical series. There was an unequal distribution of RMT laboratories between Brazilian regions and federal units. This alerts us for the surveillance of rapid molecular detection of TB in different parts of the country, with the possibility of improving the distribution of tests in areas of higher incidence in order to achieve the level of disease control recommended by national and worldwide authorities.

The Use of Xpert MTB/RIF Ultra Testing for Early Diagnosis of Tuberculosis: A Retrospective Study from a Single-Center Database

Tuberculosis (TB) is a multisystemic contagious disease produced by Mycobacterium tuberculosis complex bacteria (MTBC), with a prevalence of 65:100,000 inhabitants in Romania (six times higher than the European average). The diagnosis usually relies on the detection of MTBC in culture. Although this is a sensitive method of detection and remains the "gold standard", the results are obtained after several weeks. Nucleic acid amplification tests (NAATs), being a quick and sensitive method, represent progress in the diagnosis of TB. The aim of this study is to assess the assumption that NAAT using Xpert MTB/RIF is an efficient method of TB diagnosis and has the capacity to reduce false-positive results. Pathological samples from 862 patients with TB suspicion were tested using microscopic examination, molecular testing and bacterial culture. The results show that the Xpert MTB/RIF Ultra test has a sensitivity of 95% and a specificity of 96.4% compared with 54.8% sensitivity and 99.5% specificity for Ziehl-Neelsen stain microscopy, and an average of 30 days gained in the diagnosis of TB compared with bacterial culture. The implementation of molecular testing in TB laboratories leads to an important increase in early diagnostics of the disease and the prompter isolation and treatment of infected patients.

Comparative analysis of cartridge-based nucleic acid amplification test (CBNAAT) with conventional methods in the diagnosis of pediatric tuberculosis at a tertiary care center

BACKGROUND

Tuberculosis is an important cause of morbidity and mortality among children. Early diagnosis and treatment in children are challenging, more so in resource-limited, tuberculosis-endemic countries. In 2017, the WHO endorsed the use of CBNAAT for tuberculosis diagnosis. We have undertaken this study to evaluate the diagnostic value of CBNAAT in pediatric tuberculosis in comparison to other methods like microscopic detection of acid-fast bacilli and detection of mycobacteria-by-mycobacteria growth indicator tube (MGIT).

MATERIAL AND METHODS

This hospital-based, cross-sectional, observational prospective study was conducted in the department of pediatrics, at a tertiary care center. A detailed history, general physical examination, and relevant physical examination were performed systematically and the findings were noted in the proforma. All necessary basic investigations like CBC, ESR, X-Ray, etc., and advanced investigations like MRI, CT, and FNAC were done as per the requirement of the subjects and the results were mentioned in the study proforma. Sensitivity, specificity, positive and negative predictive value, and diagnostic accuracy were calculated for various methods. A comparison between the two methods was done using the Mc Nemar test. p-value ≤0.05 was taken as statistically significant. All statistical analyses were done using Epi info version 7.2.1.0 statistical software.

RESULTS

Among 102 children suspected to be suffering from tuberculosis, the maximum number of TB cases were found in the age group of 11-16 years (43.2%), there were 58.2% of females, 58.8% belonged to the rural population, fever (78.4%) was the most common presenting symptom and 35.3% had a history of contact. In the present study, CBNAAT and ZN staining had equal sensitivity (60.8%) and specificity (100%) while the yield for MGIT culture was quite low (sensitivity 37.3%, specificity 100%).

CONCLUSIONS

CBNAAT as a test was found to be useful, especially for early diagnosis and detection of rifampicin resistance in pediatric tuberculosis against MGIT culture. Since MGIT results become available only after 42 days and have a relatively lower yield so they can be utilized only in a selected clinical situation or in patients with high suspicion of tuberculosis where another test is not able to detect the organisms.

Clinical Evaluation of the XDR-LFC Assay for the Molecular Detection of Isoniazid, Rifampin, Fluoroquinolone, Kanamycin, Capreomycin, and Amikacin Drug Resistance in a Prospective Cohort

While the goal of universal drug susceptibility testing has been a key component of the WHO End TB Strategy, in practice, this remains inaccessible to many. Rapid molecular tests for tuberculosis (TB) and antituberculosis drug resistance could significantly improve access to testing. In this study, we evaluated the accuracy of the Akonni Biosystems XDR-TB (extensively drug-resistant TB) TruArray and lateral-flow-cell (XDR-LFC) assay (Akonni Biosystems, Inc., Frederick, MD, USA), a novel assay that detects mutations in seven genes associated with resistance to antituberculosis drugs: katG, the inhA promoter, and the ahpC promoter for isoniazid; rpoB for rifampin; gyrA for fluoroquinolones; rrs and the eis promoter for kanamycin; and rrs for capreomycin and amikacin. We evaluated assay performance using direct sputum samples from 566 participants recruited in a prospective cohort in Moldova over 2 years. The sensitivity and specificity against the phenotypic reference were both 100% for isoniazid, 99.2% and 97.9% for rifampin, 84.8% and 99.1% for fluoroquinolones, 87.0% and 84.1% for kanamycin, 54.3% and 100% for capreomycin, and 79.2% and 100% for amikacin, respectively. Whole-genome sequencing data for a subsample of 272 isolates showed 95 to 99% concordance with the XDR-LFC-reported suspected mutations. The XDR-LFC assay demonstrated a high level of accuracy for multiple drugs and met the WHO's minimum target product profile criteria for isoniazid and rifampin, while the sensitivity for fluoroquinolones and amikacin fell below target thresholds, likely due to the absence of a gyrB target in the assay. With optimization, the XDR-LFC shows promise as a novel near-patient technology to rapidly diagnose drug-resistant tuberculosis.

Comparing Mycobacterium tuberculosis RNA Accuracy in Various Respiratory Specimens for the Rapid Diagnosis of Pulmonary Tuberculosis

Objective

To evaluate the rapid diagnostic accuracy of Mycobacterium tuberculosis RNA (TB-RNA) for pulmonary tuberculosis (PTB) in a large patient sample and to evaluate the difference in TB-RNA diagnostic accuracy in various respiratory specimens.

Methods

Patient medical records were retrospectively reviewed to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of the acid-fast bacillus (AFB) smear and TB-RNA to evaluate their diagnostic accuracy against final clinical diagnosis.

Results

Of the 2336 patients ultimately included, 1123 provided 1 sputum specimen each and 1213 provided 1 bronchoalveolar lavage fluid (BALF) specimen each. The overall sensitivity, specificity, PPV, NPV, and AUC of the AFB smear were 36.2%, 86.4%, 90.6%, 27.3%, and 0.61, respectively. The overall sensitivity, specificity, PPV, NPV, and AUC of TB-RNA for the rapid detection of PTB were 57.4%, 99.4%, 99.7%, 39.3%, and 0.78, respectively. When sputum and BALF specimens were used for AFB smear testing, the sensitivity, specificity, PPV, NPV, and AUC of the AFB smear were 44.5%, 81.5%, 87.5%, 33.5%, and 0.63; and 29.2%, 92.7%, 94.8%, 22.5%, and 0.61, respectively. The sensitivity, specificity, PPV, NPV, and AUC of TB-RNA for the rapid detection of PTB using sputum were 49.6%, 99.3%, 99.5%, 40.4%, and 0.74, respectively; whereas those of TB-RNA determined using BALF were 63.9%, 99.5%, 99.8%, 38.0%, and 0.82, respectively.

Conclusion

The diagnostic accuracy of TB-RNA for PTB was moderate and considerably better than that of the AFB smear. The diagnostic accuracy of TB-RNA for various respiratory specimens differed; the diagnostic accuracy of TB-RNA for BALF specimens was substantially better than that for sputum samples, and BALF specimens were more suitable for TB-RNA.

Nucleic Acids Detection for Mycobacterium tuberculosis Based on Gold Nanoparticles Counting and Rolling-Circle Amplification

Tuberculosis (TB) is a common infectious disease caused by Mycobacterium tuberculosis, which usually disturbs the lungs, and remains the second leading cause of death from an infectious disease worldwide after the human immunodeficiency virus. Herein, we constructed a simple and sensitive method for Mycobacterium tuberculosis-specific DNA detection with the dark-field microscopic imaging of gold nanoparticles (AuNPs) counting strategy and rolling-circle amplification (RCA). Taking advantage of RCA amplification, one target molecule produced hundreds of general oligonucleotides, which could form the sandwich structure with capture-strand-modified magnetic beads and AuNPs. After magnetic separation, AuNPs were released and detected by dark-field imaging; about 10 fM Mycobacterium tuberculosis-specific DNA target can still be differentiated from the blank. No significant change of the absorbance signals was observed when the target DNA to genomic DNA ratio (in mass) was from 1:0 to 1:10⁶. The spike recovery results in genomic DNA from human and Klebsiella pneumoniae suggested that the proposed method has the feasibility for application with biological samples. This proposed method is performed on an entry-level dark-field microscope setup with only a 6 μL detection volume, which creates a new, simple, sensitive, and valuable tool for pathogen detection.

A Comprehensive Evaluation of a Loop-Mediated Isothermal Amplification Assay for the Diagnosis of Pulmonary Tuberculosis in Children Using Bronchoalveolar Lavage Fluid

Objective

Using TB-LAMP for diagnosing pediatric PTB, however, still requires systematic evaluation. Here, we evaluated TB-LAMP performance alone and in combination with conventional assays for diagnosing PTB in Chinese children, using mycobacterial culture or CCRS (the composite clinical reference standard) as references.

Design or Methods

BALF samples were collected at Shenyang Tenth People’s Hospital from 251 children susceptible to TB infection with indications for fiberoptic bronchoscopy.

Results

When mycobacterial culture was the reference, TB-LAMP used alongside smear microscopy doubled sensitivity for detecting pediatric PTB compared with smear microscopy alone (82.5% vs 40.0%). When CCRS was the reference, AFB microscopy, MTB culture, and TB-LAMP had sensitivities of 16.5%, 30.1%, and 51.1%, respectively, and specificities of 98.2%, 100.0%, and 99.1%. Combining MTB culture with TB-LAMP gave a sensitivity of 61.1% and specificity of 96.6%. TB-LAMP identified 39.3% and 43.2% of cases with negative MTB culture or AFB microscopy results.

Conclusion

TB-LAMP using BALF samples provided faster results, allowing early and accurate PTB diagnosis. Our findings provide insights for optimizing diagnostic algorithms for pediatric PTB.

Performance of Xpert MTB/RIF Ultra for the Diagnosis of Pulmonary Tuberculosis Using Bronchoalveolar Lavage Samples in People Living with HIV/AIDS (PLWHA) in China: A Prospective Study

Background

Sputum is commonly used for the diagnostic testing of pulmonary tuberculosis (PTB), but people living with HIV/AIDS (PLWHA) usually have little sputum. Moreover, the automated molecular test, Xpert MTB/RIF assay (Xpert), has a low sensitivity in PLWHA. We aimed to estimate the performance of Xpert Ultra on the detection of Mycobacterium tuberculosis (MTB) using bronchoalveolar lavage (BAL).

Methods

From February 5, 2018 to March 30, 2019, a total of 99 PLWHA with suspected PTB at the Third People’s Hospital of Shenzhen, China, were recruited. The information on demographics and medical history, blood MTB antigen-specific interferon gamma enzyme-linked immunospot assay (T-SPOT.TB), T lymphocyte subsets, and plasma HIV RNA load were collected. Computed tomography (CT) and flexible bronchoscopy were performed, and BAL and blood samples were collected. Testing of acid-fast bacilli (AFB), tuberculosis real-time fluorescence quantitative PCR (TBDNA), Ultra, Xpert, and MTB culture were conducted.

Results

Compared to BAL MTB culture for tuberculosis diagnosis, Ultra, Xpert, T-SPOT.TB, TBDNA and AFB smear had the sensitivity of 0.96 (24/25), 0.80 (20/25), 0.84 (21/25), 0.44 (11/25), and 0.12 (3/25), respectively; and the specificity of 0.92 (68/74), 0.96 (71/74), 0.93 (69/74), 0.96 (71/74), and 0.99 (73/74), respectively. Our study found that the sensitivity of Ultra was higher than that of culture and Xpert (AUC 0.92, 0.86 and 0.84, respectively). The results also indicated that PLWHA with CD4 <200 cells/mm³ had reduced both sensitivity (from 1.00 and 0.86 to 0.94 and 0.78, respectively) and specificity (from 0.96 and 1.00 to 0.90 and 0.41, respectively) of Ultra and Xpert for the diagnosis of PTB.

Discussion

Our data supported an increased sensitivity of Ultra compared to that of Xpert on BAL samples of PLWHA, regardless of the CD4 counts and reference diagnosis standards.

Behind Every Great Infection Prevention Program is a Great Microbiology Laboratory: Key Components and Strategies for an Effective Partnership

A great clinical microbiology laboratory supporting a great infection prevention program requires focusing on the following services: rapid and accurate identification of pathogens associated with health care-associated infections; asymptomatic surveillance for health care-acquired pathogens before infections arise; routine use of broad and flexible antimicrobial susceptibility testing to direct optimal therapy; implementation of epidemiologic tracking tools to identify outbreaks; development of clear result communication with interpretative comments for clinicians. These goals are best realized in a collaborative relationship with the infection prevention program so that both can benefit from the shared priorities of providing the best patient care.

GeneXpert on patients with human immunodeficiency virus and smear-negative pulmonary tuberculosis

Objectives

Vietnam is a high-prevalence country for tuberculosis (TB). Xpert MTB/RIF is a novel PCR-based diagnostic test that is substantially more sensitive for detecting M. tuberculosis than traditional smear-based techniques. However, locally-derived evidence of Xpert MTB/RIF in HIV-infected people is limited. This study evaluates the performance of the Xpert MTB/RIF in HIV-infected patients with smear-negative pulmonary TB (SNTB).

Methods

This was a cross-sectional study in 3 hospitals. The performance of Xpert MTB/RIF was compared with the reference standard of liquid culture and phenotypic drug-susceptibility testing for rifampicin (RIF) resistance.

Results

Out of 123 patients, the median age was 37.0 (IQR: 32.0–41.0) and 81.3% were male. The area under the receiver operating characteristic curve, sensitivity (Se) and specificity (Sp) of Xpert MTB/RIF for pulmonary TB diagnosis were 0.72 (95% confidence interval [CI]: 0.63–0.81), 66.7% (95%CI: 54.8–77.1) and 77.1% (95%CI: 62.7–88.0), respectively, while Se and Sp of Xpert MTB/RIF in detecting RIF resistance were 50.0 (11.8–88.2) and 86.4% (95%CI: 72.7–94.8).

Conclusion

The performance of Xpert MTB/RIF in HIV-infected patients with SNTB for the diagnosis of TB and RIF-resistance was low. Further studies are required to evaluate the results of Xpert MTB/RIF assay in HIV-infected patients with SNTB and the role of Xpert repetition on the same specimens.

Evaluation of screening strategies for pulmonary tuberculosis among hospitalized patients in a low-burden setting: cost-effectiveness of GeneXpert MTB/RIF compared to smear microscopy

OBJECTIVE

Hospitalized patients undergoing evaluation for pulmonary tuberculosis (TB) require airborne isolation while testing for Mycobacterium tuberculosis (MTB) to reduce risk of nosocomial transmission. GeneXpert MTB/RIF (Xpert) is more rapid and accurate than sputum smear microscopy, but it is not routinely used to 'rule out' infectious pulmonary TB among hospitalized patients in the United States. We sought to evaluate the diagnostic performance and cost-effectiveness of Xpert-based TB evaluation.

METHODS

We conducted a retrospective cohort study of hospitalized adults evaluated for pulmonary TB at a large academic medical center in New York from 2010 to 2017. Using propensity score matching, we compared hospital length-of-stay among patients undergoing conventional smear-based TB evaluation to a control group with non-TB pneumonia. We performed a probabilistic cost-effectiveness analysis to compare Xpert-based versus conventional TB evaluation.

RESULTS

In total 1,421 patients were evaluated for TB with airborne isolation and sputum testing; mycobacterial culture was positive for MTB in 49 (3.4%). Conventional TB evaluation was associated with an increase of 4.4 hospital days compared to propensity-matched controls. Xpert-based testing strategies dominated conventional TB evaluation with a cost savings of $5,947 (95% CI, $1,156-$12,540) and $4,445 (95% CI, $696-$9,526) per patient depending on the number of Xpert tests performed (1 vs 2, respectively) and assumptions about the reduction of length of stay achieved.

CONCLUSIONS

In the evaluation of hospitalized patients for pulmonary TB, Xpert-based testing has superior diagnostic performance and is likely cost-effective compared to smear microscopy due to reduced hospital length-of-stay associated with more rapid test results.

Development and Validation of Signature Sequence-Based PCR for Improved Molecular Diagnosis of Tuberculosis

Reliable, fast, and affordable diagnosis for tuberculosis (TB) remains a challenge to reduce disease incidence in resource-poor countries. Tests based on nucleotide sequences that are signature to Mycobacterium tuberculosis have the potential to make a positive impact on case detection rates, which can eventually help control TB. Using extensive comparative bioinformatics approach, we mined the genome for M. tuberculosis-specific genes and identified four genes so-called signature sequence (SS). With <25% homology with other known genes/proteins of mycobacterial/nonmycobacterial origin in various databases, these SS genes are ideal targets for species-specific identification. Sputum from suspected patients was liquefied using novel complete liquefying reagent, and DNA was isolated. Samples from patients (n = 417), reporting to TB clinics at two different hospitals, which met our inclusion criteria, were collected for this study. A small number (n = 143) was used for initial standardization, and the remaining patient samples (n = 274) were evaluated by SS and compared with smear microscopy, GeneXpert, culture, and clinical outcome. An overwhelming sensitivity of 97.0%, significantly higher than GeneXpert (95.0%), was seen. SS could pick all smear-negative, but culture-positive samples, along with other culture-negative samples; some of the latter were declared clinically positive. Our results yielded superior sensitivity and specificity through conventional PCR.

Tuberculosis Screening, Testing, and Treatment of US Health Care Personnel: ACOEM and NTCA Joint Task Force on Implementation of the 2019 MMWR Recommendations

: On May 17, 2019, the US Centers for Disease Control and Prevention and National Tuberculosis Controllers Association issued new Recommendations for Tuberculosis Screening, Testing, and Treatment of Health Care Personnel, United States, 2019, updating the health care personnel-related sections of the Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005. This companion document offers the collective effort and experience of occupational health, infectious disease, and public health experts from major academic and public health institutions across the United States and expands on each section of the 2019 recommendations to provide clarifications, explanations, and considerations that go beyond the 2019 recommendations to answer questions that may arise and to offer strategies for implementation.

TB-QUICK: CRISPR-Cas12b-assisted rapid and sensitive detection of Mycobacterium tuberculosis

OBJECTIVES

Tuberculosis (TB) remains one of the public health problems worldwide. Rapid, sensitive and cost-effective diagnosis of Mycobacterium tuberculosis (M.tb) is critical for TB control.

METHODS

We developed a novel M.tb DNA detection platform (nominated as TB-QUICK) which combined loop-mediated isothermal amplification (LAMP) and CRISPR-Cas12b detection. TB-QUICK was performed on pulmonary or plasma samples collected from 138 pulmonary TB (PTB) patients, 21 non-TB patients and 61 close contacts to TB patients. Acid-fast bacillus (AFB) smear, M.tb culture and GeneXpert MTB/RIF (Xpert) assays were routinely conducted in parallel.

RESULTS

By targeting M.tb IS6110, TB-QUICK platform could detect as low as 1.3 copy/μL M.tb DNA within 2 h. In pulmonary TB samples, TB-QUICK exhibited improved overall sensitivity of 86.8% over M.tb culture (66.7%) and Xpert (70.4%), with the specificity of 95.2%. More significantly, TB-QUICK exhibited a superior sensitivity in AFB-negative samples (80.5%) compared to Xpert (57.1%) and M.tb culture (46.2%). In the detection of plasma M.tb DNA by TB-QUICK, 41.2% sensitivity for AFB-positive and 31.7% for AFB-negative patients were achieved.

CONCLUSION

In conclusion, TB-QUICK exhibits rapidity and sensitivity for M.tb DNA detection with the superiority in smear-negative paucibacillary TB patients. The clinical application of TB-QUICK in TB diagnosis needs to be further validated in larger cohort.

Performance of GeneXpert MTB/RIF for Diagnosing Tuberculosis Among Symptomatic Household Contacts of Index Patients in South Africa

BACKGROUND

We describe the performance of GeneXpert MTB/RIF (Xpert) for diagnosing tuberculosis (TB) among symptomatic household contacts (HHCs) of rifampicin-resistant and drug-sensitive index cases.

METHODS

We conducted a cross-sectional study among HHCs of recently diagnosed (<2 weeks) smear-positive and Xpert-positive index cases in the Bojanala District, South Africa. The HHCs were screened for TB symptoms; persons with ≥1 TB symptom provided 1 sputum for smear microscopy, Xpert, and mycobacterial growth indicator tube (MGIT) culture. Diagnostic test performance of Xpert was determined using MGIT as the reference standard.

RESULTS

From August 2013 to July 2015, 619 HHCs from 216 index cases were enrolled: 60.6% were female, median age was 22 years (interquartile range, 9-40), and 126 (20.4%) self-reported/tested human immunodeficiency virus positive. A total of 54.3% (336 of 619) of contacts had ≥1 TB symptom (cough, fever, night sweats, weight loss), 297 of 336 (88.4%) of which provided a sputum; 289 (97.3%) had complete testing and 271 were included in the analysis. In total, 42 (6.8%) of 619 HHCs had microbiologically confirmed TB. The MGIT identified 33 HHCs as positive for Mycobacterium tuberculosis; of these, 7 were positive on Xpert resulting in a sensitivity of 21.2% (95% confidence interval [CI], 9.0-38.9), specificity of 98.3% (95% CI, 95.6-99.5), positive predictive value of 63.6% (95% CI, 30.8-89.1), and negative predictive value of 90.0 (95% CI, 85.7-93.4).

CONCLUSIONS

Among symptomatic HHCs investigated for TB, Xpert performed suboptimally compared with MGIT culture. The poor performance of Xpert for diagnosing TB suggests that a more sensitive test, such a Xpert Ultra or culture, may be needed to improve yield of contact investigation, where feasible.

Prevalence of rifampicin resistance tuberculosis among HIV/TB coinfected patients in Benue State, Nigeria

Introduction

the emergence of HIV/TB co-infection has changed the global health landscape globally, particularly in sub-Saharan Africa and Asia with a high prevalence rate. It has further worsened and compound patient diagnosis, treatment/management approach and infection control. Rifampicin resistance TB (RR-TB) is a good indicator of treatment failure and infection control in the community. This study determines the prevalence of RR-TB among HIV/TB coinfected patients in Benue State, Nigeria.

Methods

the case-control study was carried out at Federal Medical Centre, Makurdi and General Hospital, Otupko, between January 2017 and February 2018. One thousand and ten suspected tuberculosis and HIV patients were enrolled in the study, diagnosed according to WHO guidelines. Sputum samples were collected and then analyzed by acid-fast bacilli smear test and GeneXpert MTB/RIF assay.

Results

overall prevalence of tuberculosis by acid-fast test was 74 (7.3%), 171 (16.93%) by GeneXpert assay and 2.18% by RR-TB test respectively. Significant difference was observed between the detection technique and demographic variables, high prevalence among urban patient compared to rural (8.85%vs 5.40%; X²= 4.38; P = 0.036) and ethnic background of the patients (X²= 23.21; P = 0.000) by acid fast test. With GeneXpert, high prevalence recorded among patient within age-group15-45years (X²= 8.01; P = 0.046) and ethnic group (X²= 6.30; P = 0.044). The occurrence of HIV/TB co-infection was less associated with Idoma ethnic group (COR; 0.440; 95% C.I; 0.246 - 0.786).

Conclusion

the relatively high prevalence of HIV/TB co-infection and RR-TB is a tremendous public health threat, considering society's attendant implication. Further surveillance studies are needed to evaluate the situation in Benue State better.

Improving tuberculosis management in prisons: Impact of a rapid molecular point-of-care test

OBJECTIVE

To improve tuberculosis (TB) diagnosis in prison, we evaluate the value of the Xpert^ⓇMTB/RIF Ultra assay (Xpert) as point-of-care (POC) in a French prison hospital.

METHODS

We first validated Xpert use on raw sputum at the referent laboratory. Secondly, trained physicians at the prison hospital performed Xpert tests for each patient presenting TB symptoms. The results were compared with Xpert, microscopic examination, culture and drug susceptibility testing on the corresponding decontaminated specimens.

RESULTS

76 inmates were included in 15 months and 21 were diagnosed with TB. The overall sensitivity, specificity, positive and negative predictive values of Xpert were respectively: 92.3%, 100%, 100% and 98.7% on raw sputum. The efficiency of the molecular POC was confirmed by a concordance of 97% between Xpert findings from the prison hospital and culture results. Delay of microbiological diagnosis was reduced by about 18 days for 13 inmates with smear-negative sputum that avoid the mobilization of major means (escort, transport) to perform fibroscopic samples. Repeated Xpert negative results helped to speed the lifting of inmate isolation.

CONCLUSIONS

The implementation of Xpert in prison could optimize the management of incarcerated patients and thus limit the spread of TB among inmates, carers and other staff.

Prevalence of Nontuberculous Mycobacterium Infections versus Tuberculosis among Autopsied HIV Patients in Sub-Saharan Africa: A Systematic Review and Meta-Analysis

In industrialized countries, Mycobacterium avium complex and other nontuberculous mycobacteria (NTM) are major causes of opportunistic infection-related deaths in HIV patients. However, in resource-limited regions, data on NTM are scarce, and tuberculosis (TB) was often assumed to be the cause of death in HIV patients with a positive acid-fast smear. We searched MEDLINE and Embase databases for studies on autopsied HIV patients in sub-Saharan Africa published between January 1997 and April 2020. We included studies that reported histopathological or microbiological evidences for diagnosis of TB and NTM infection. We excluded articles without mycobacterial evidence from culture or molecular testing, such as those that used verbal autopsy, death certificates, or national registry data (systematic review registration number: CRD42019129836 at PROSPERO). We included six eligible studies that reported 391 autopsies in sub-Saharan African HIV patients. The prevalence of NTM and TB at autopsy ranged from 1.3% to 27.3% and 11.8% to 48.7%, respectively. The weighted prevalence ratio of NTM versus TB was 0.16 indicating that for every seven HIV patients died with mycobacterial infections, there was one died with NTM infection. Of the 13 NTM infections, six were caused by M. avium complex. Mycobacterium avium complex and other NTM infections are important differential diagnoses of TB at the time of death among HIV patients in sub-Saharan Africa. Our findings highlight the need to systematically survey the prevalence of NTM infections among HIV patients seeking medical care in resource-limited regions.

Long-Term GeneXpert Positivity after Treatment for Pulmonary Tuberculosis

Tuberculosis (TB) is a cause of ill health and death worldwide. Since 2010, the diagnostic process has strongly relied on GeneXpert assays on biological specimens. Xpert MTB/RIF is an automated nucleic acid amplification test (NAAT) for Mycobacterium tuberculosis and rifampicin resistance, endorsed by the World Health Organization and the US Food and Drug Administration. Xpert is used in many countries as the initial diagnostic test for tuberculosis. Nevertheless, the reliability of GeneXpert positive tests in patients with a history of TB is largely unknown, due to possible false-positive results (i.e., GeneXpert-positive but culture-negative patients). We present a case report of a patient with a history of pulmonary TB, who was GeneXpert positive but culture negative on bronchoalveolar lavage 22 months after completion of appropriate antitubercular therapy.

LEARNING POINTS

GeneXpert assays have a pivotal role in the diagnosis of tuberculosis (TB), with overall good sensitivity and excellent specificity.Patients with a history of TB can be GeneXpert positive up to several years after the end of appropriate antitubercular treatment.Further studies are warranted to fully understand the role of GeneXpert assays in the diagnostic algorithms of patients with a history of TB.

Pulmonary tuberculosis: Evaluation of current diagnostic strategy

OBJECTIVE

To identify tools that will result in faster diagnosis, making the current pulmonary tuberculosis strategy more efficient.

PATIENTS AND METHODS

A 4-year (2015-2018) retrospective study. The gold standard for diagnosis was a positive culture from a respiratory specimen. All sputum, fibroscopy and post-fibroscopy specimens (for smear negative patients) were collected. Each specimen was analyzed through smear examination and culture. All nucleic acid amplification testing results were included. Analyses looked at the incremental yield of positive cases of each successive specimen collection, and time to diagnosis.

RESULTS

A total of 354 patients had at least one positive culture. Sputum allowed a diagnosis in 92% of cases (including a gain in sensitivity of around 7% for the third sputum specimen), with 160 smear-positive patients (45%). Among smear-negative patients, 109 underwent a fibroscopy procedure (culture sensitivity of 75%), and 59 had a post-fibroscopy specimen collected, which together identified the rest of the patients (8%). Molecular testing was used in 237 specimens. Median time to diagnosis was 11 days, which was significantly reduced among smear-negative patients when molecular testing was used (P<0.001). Shortening the delay between sputum specimen collections did not alter procedure sensitivity.

CONCLUSIONS

We identified several aspects of the French tuberculosis diagnosis algorithm that could be improved, and posed the basis for a prospective study. Centers in higher incidence areas could benefit from a dedicated, predefined procedure exploring suspicions of tuberculosis. A high suspicion score of tuberculosis could drive the reasoned use of molecular testing in such settings.

Evaluation of the Xpert MTB/RIF test accuracy for diagnosis of tuberculosis in areas with a moderate tuberculosis burden

The Xpert MTB/RIF assay (Xpert) is a molecular assay used for direct detection of Mycobacterium tuberculosis (MTB) in clinical specimens. In this study, we aimed to assess the accuracy of the Xpert assay for the diagnosis of tuberculosis (TB) in TB suspected patients from the northern region of Iran. The obtained results were compared with the culture method. The sputum specimens were examined using the Xpert assay, smear microscopy, and solid culture media as a reference diagnostic tool. Among 293 presumptive TB cases, 92 (31.4%) were positive according to the culture method. The Xpert method detected 88 (95.7%) cases that were positive according to the culture method, compared with 78 (84.8%) positive cases according to smear microscopy. The overall sensitivity and specificity of the Xpert method for TB diagnosis were 95.7% and 99%, respectively. Also, the sensitivity and specificity for smear microscopy were 84.8% and 97.5%, respectively. The Xpert assay showed high overall sensitivity and specificity; thus, it can be effectively used for the early and accurate diagnosis of MTB in TB endemic areas. In addition, the agreement between semi-quantitative results of Xpert and smear microscopy assays could be helpful in evaluating transmission potential in TB patients.

Which sample type is better for Xpert MTB/RIF to diagnose adult and pediatric pulmonary tuberculosis?

Objective: This review aimed to identify proper respiratory-related sample types for adult and pediatric pulmonary tuberculosis (PTB), respectively, by comparing performance of Xpert MTB/RIF when using bronchoalveolar lavage (BAL), induced sputum (IS), expectorated sputum (ES), nasopharyngeal aspirates (NPAs), and gastric aspiration (GA) as sample.

Methods: Articles were searched in Web of Science, PubMed, and Ovid from inception up to 29 June 2020. Pooled sensitivity and specificity were calculated, each with a 95% confidence interval (CI). Quality assessment and heterogeneity evaluation across included studies were performed.

Results: A total of 50 articles were included. The respective sensitivity and specificity were 87% (95% CI: 0.84–0.89), 91% (95% CI: 0.90–0.92) and 95% (95% CI: 0.93–0.97) in the adult BAL group; 90% (95% CI: 0.88–0.91), 98% (95% CI: 0.97–0.98) and 97% (95% CI: 0.95–0.99) in the adult ES group; 86% (95% CI: 0.84–0.89) and 97% (95% CI: 0.96–0.98) in the adult IS group. Xpert MTB/RIF showed the sensitivity and specificity of 14% (95% CI: 0.10–0.19) and 99% (95% CI: 0.97–1.00) in the pediatric ES group; 80% (95% CI: 0.72–0.87) and 94% (95% CI: 0.92–0.95) in the pediatric GA group; 67% (95% CI: 0.62–0.72) and 99% (95% CI: 0.98–0.99) in the pediatric IS group; and 54% (95% CI: 0.43–0.64) and 99% (95% CI: 0.97–0.99) in the pediatric NPA group. The heterogeneity across included studies was deemed acceptable.

Conclusion: Considering diagnostic accuracy, cost and sampling process, ES was a better choice than other sample types for diagnosing adult PTB, especially HIV-associated PTB. GA might be more suitable than other sample types for diagnosing pediatric PTB. The actual choice of sample types should also consider the needs of specific situations.

Performances and usefulness of Xpert MTB/RIF assay in low-incidence settings: not that bad?

Xpert MTB/RIF assay, a real-time PCR assay designed to detect Mycobacterium tuberculosis, has proven sensitive and specific when performed on respiratory samples in a high prevalence setting. However, it was suggested as less accurate in a low-incidence environment. We evaluated the accuracy of the Xpert for the diagnosis of tuberculosis (TB) on pulmonary and extrapulmonary samples in Geneva (Switzerland), where the prevalence of active TB is very low. From March 2009 to February 2013, the Xpert was performed on clinical samples. All specimens were also processed using auramine, AFB staining, and mycobacterial culture with both solid and liquid media. The accuracy of both microscopy and Xpert was determined retrospectively using cultures as the reference method. A total of 732 clinical specimens were processed with the Xpert. The Xpert had a high specificity (97.5%; 95% confidence interval (CI), 95.8-98.5%) and revealed much more sensitive (82.7%; 95% CI, 74.1-89.0%) than microscopy (55.5%; 95% CI, 45.7-64.8%) for the diagnosis of TB, with a high negative predictive value (96.8%; 95% CI, 95.0-98.0%). The advantage of PCR over microscopy was even more pronounced for extrapulmonary specimens (sensitivity of 70% (95% CI, 50.4-84.6%) compared with 23.3% (95% CI, 10.6-42.7%)). Despite the low prevalence of TB in Switzerland, results performance for respiratory samples was similar to that reported in high prevalence countries. The high negative predictive value is clinically helpful in our setting, where pulmonary TB needs to be reasonably ruled out. When considering extrapulmonary samples, microscopy performed poorly compared with Xpert. This study shows that the Xpert remains accurate and useful in a low-incidence setting.

Addressing the threat from within: Investigation of respiratory symptoms in a health care worker with untreated latent tuberculosis infection

Tuberculosis (TB) in the health care worker demands orchestrated efforts from health care institutions to promptly identify cases and address community risk. We describe a pediatric intensive care unit nurse with latent TB infection who developed hemoptysis and a lung infiltrate concerning for active TB. Her evaluation and contact investigation were facilitated by our institution's command center. Although TB was ultimately ruled out, this case tested our team-based care in response to a suspected high-consequence pathogen.

Use of GeneXpert MTB/RIF on a single pooled sputum specimen to exclude pulmonary tuberculosis among hospital inpatients placed in respiratory isolation

BACKGROUND

Patients with suspected pulmonary tuberculosis (PTB) are usually placed in respiratory isolation awaiting three sputum smear microscopy results for acid-fast bacilli (3AFB). GeneXpert MTB/RIF (Xpert) on a pooled sample from two sputa may allow for more rapid de-isolation.

OBJECTIVES

To compare the sensitivity and negative predictive value (NPV) of Xpert performed on a single pooled sputum sample ('pooled Xpert') to 3AFB, in order to exclude PTB in patients placed in respiratory isolation.

METHODS

Hospital inpatients in respiratory isolation for possible PTB were enrolled prospectively. Three expectorated sputum samples were obtained for smear microscopy. Two of the same samples had 0.5 ml removed from each and pooled for pooled Xpert. The diagnostic accuracy of pooled Xpert and 3AFB were assessed and compared to liquid culture at 8 weeks as the reference standard.

RESULTS

Of 56 participants, nine (16.1%) were diagnosed with PTB. Compared to liquid culture, pooled Xpert had a sensitivity of 88.9% (95% confidence interval (CI) 57-99%) and NPV of 97.9% (95% CI 89-99%). 3AFB had a sensitivity of 66.7% (95% CI 35-88%) and NPV of 93.5% (95% CI 83-98%).

CONCLUSIONS

A single pooled Xpert was non-inferior to 3AFB, with a strong trend towards greater sensitivity and better NPV. These findings support the use of a single pooled Xpert as an effective rapid screening approach for ruling out PTB in low incidence settings. Its value in high incidence settings and optimal combination with smear microscopy and culture warrant further evaluation.

How Can the Tuberculosis Laboratory Aid in the Patient-Centered Diagnosis and Management of Tuberculosis?

In 2019, tuberculosis is still a global source of morbidity and mortality. To determine and provide the most effective treatment regimen to patients, the tuberculosis laboratory needs to rapidly but reliably answer 2 main questions: (1) Is Mycobacterium tuberculosis detectable in the patient specimen? and (2) If so, is the strain detected drug susceptible or does it show any form of drug resistance? In cases of drug resistance, health care providers need to have access to minimal inhibitory concentration results and to the type of mutation conferring drug resistance to tailor the most appropriate drug regimen.

Transmission of Mycobacterium tuberculosis From Patients Who Are Nucleic Acid Amplification Test Negative

Background

Among adults with signs and symptoms of pulmonary tuberculosis (TB), recognition of transmissible TB has implications for airborne infection isolation and public health activities. Sputum smear-negative TB patients account for around one-fifth of tuberculosis transmission. The tuberculosis transmission risk of TB patients with negative results on nucleic acid amplification test (NAAT) of respiratory specimens has not been established. We sought to estimate the tuberculosis transmission risk of NAAT-negative TB patients.

Methods

We retrospectively reviewed Maryland TB program data collected from 2004 to 2009, during which time NAAT using the Mycobacterium Tuberculosis Direct Test (MTD) was performed routinely. Patients with sputum Mycobacterium tuberculosis (M.tb) isolates having matching genotypes were assigned to clusters. Transmission sequence was approximated by collection order of individuals' first culture-positive specimens. Minimum transmission risks of NAAT (MTD)-negative TB patients and of smear-negative TB patients were estimated based on individuals' positions within clusters.

Results

Among 809 patients with culture-confirmed TB, M.tb genotypes were available for 782 (96.7%). For NAA-negative TB patients, the minimum transmission risk estimate was 5.1% (95% CI 0-11.4). For smear-negative TB patients, the minimum transmission risk estimate was 11.2% (95% CI 7.2-15.3).

Conclusions

Minimum transmission risk of NAAT-negative TB patients was lower than that of smear-negative TB patients. However, transmission risk of NAA-negative TB patients appears to not be negligible.

Xpert MTB/RIF assay for the diagnosis of rifampicin resistance in different regions: a meta-analysis

Background

To estimate the diagnostic accuracy of Xpert MTB/RIF for rifampicin resistance in different regions, a meta-analysis was carried out.

Methods

Several databases were searched for relevant studies up to March 3, 2019. A bivariate random-effects model was used to estimate the diagnostic accuracy.

Results

We identified 97 studies involving 26,037 samples for the diagnosis of rifampicin resistance. The pooled sensitivity, specificity and AUC of Xpert MTB/RIF for rifampicin resistance detection were 0.93 (95% CI 0.90–0.95), 0.98 (95% CI 0.96–0.98) and 0.99 (95% CI 0.97–0.99), respectively. For different regions, the pooled sensitivity were 0.94(95% CI 0.89–0.97) and 0.92 (95% CI 0.88–0.94), the pooled specificity were 0.98 (95% CI 0.94–1.00) and 0.98 (95% CI 0.96–0.99), and the AUC were 0.99 (95% CI 0.98–1.00) and 0.99 (95% CI 0.97–0.99) in high and middle/low income countries, respectively. The pooled sensitivity were 0.91 (95% CI 0.87–0.94) and 0.91 (95% CI 0.86–0.94), the pooled specificity were 0.98 (95% CI 0.96–0.99) and 0.98 (95% CI 0.96–0.99), and the AUC were 0.98 (95% CI 0.97–0.99) and 0.99 (95% CI 0.97–0.99) in high TB burden and middle/low prevalence countries, respectively.

Conclusions

The diagnostic accuracy of Xpert MTB/RIF for rifampicin resistance detection was excellent.

The effect of sputum quality and volume on the yield of bacteriologically-confirmed TB by Xpert MTB/RIF and smear

Introduction

The World Health Organization endorsed (2010) the use of Xpert MTB/RIF and countries are shifting from smear microscopy (smear)-based to Xpert MTB/RIF-based tuberculosis (TB) diagnostic algorithms. As with smear, sputum quality may predict the likelihood of obtaining a bacteriologically-confirmed TB when using Xpert MTB/RIF.

Methods

From 08/12-11/2014, all people living with HIV were recruited at 22 clinics. For patients screened positive using the four TB symptoms their sputa were tested by Xpert MTB/RIF and smear. Laboratorians assessed and recorded sputum appearance and volume. The yield of bacteriologically-positive sputum evaluated using Xpert MTB/RIF and smear, likelihood-ratios were calculated.

Results

Among 6,041 patients enrolled 2,296 were presumptive TB, 1,305 (56.8%) had > 1 sputa collected and 644/1,305 (49.3%) had both Xpert MTB/RIF and smear results. Since >1 sputa collected from 644 patients 954 sputa were tested by Xpert MTB/RIF and smear. Bacteriologically-positive sputum was two-fold higher with Xpert MTB/RIF 11.4% versus smear 5.3%, p < 0.001. Sputum appearance and quantity were not predictive of bacteriologically-positive results, except volume of 2ml to < 3ml, tested by Xpert MTB/RIF LR+= 1.26 (95% CI, 1.05–1.50).

Conclusion

Xpert MTB/RIF test yield to bacteriologically-positive sputum was superior to smear. Sputum quality and quantity, however, were not consistently predictive of bacteriologically-positive results by Xpert MTB/RIF or smear.

Xpert MTB/RIF and Xpert MTB/RIF Ultra for pulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Xpert MTB/RIF (Xpert MTB/RIF) and Xpert MTB/RIF Ultra (Xpert Ultra), the newest version, are the only World Health Organization (WHO)-recommended rapid tests that simultaneously detect tuberculosis and rifampicin resistance in persons with signs and symptoms of tuberculosis, at lower health system levels. A previous Cochrane Review found Xpert MTB/RIF sensitive and specific for tuberculosis (Steingart 2014). Since the previous review, new studies have been published. We performed a review update for an upcoming WHO policy review.

OBJECTIVES

To determine diagnostic accuracy of Xpert MTB/RIF and Xpert Ultra for tuberculosis in adults with presumptive pulmonary tuberculosis (PTB) and for rifampicin resistance in adults with presumptive rifampicin-resistant tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, to 11 October 2018, without language restriction.

SELECTION CRITERIA

Randomized trials, cross-sectional, and cohort studies using respiratory specimens that evaluated Xpert MTB/RIF, Xpert Ultra, or both against the reference standard, culture for tuberculosis and culture-based drug susceptibility testing or MTBDRplus for rifampicin resistance.

DATA COLLECTION AND ANALYSIS

Four review authors independently extracted data using a standardized form. When possible, we also extracted data by smear and HIV status. We assessed study quality using QUADAS-2 and performed meta-analyses to estimate pooled sensitivity and specificity separately for tuberculosis and rifampicin resistance. We investigated potential sources of heterogeneity. Most analyses used a bivariate random-effects model. For tuberculosis detection, we first estimated accuracy using all included studies and then only the subset of studies where participants were unselected, i.e. not selected based on prior microscopy testing.

MAIN RESULTS

We identified in total 95 studies (77 new studies since the previous review): 86 studies (42,091 participants) evaluated Xpert MTB/RIF for tuberculosis and 57 studies (8287 participants) for rifampicin resistance. One study compared Xpert MTB/RIF and Xpert Ultra on the same participant specimen.Tuberculosis detectionOf the total 86 studies, 45 took place in high tuberculosis burden and 50 in high TB/HIV burden countries. Most studies had low risk of bias.Xpert MTB/RIF pooled sensitivity and specificity (95% credible Interval (CrI)) were 85% (82% to 88%) and 98% (97% to 98%), (70 studies, 37,237 unselected participants; high-certainty evidence). We found similar accuracy when we included all studies.For a population of 1000 people where 100 have tuberculosis on culture, 103 would be Xpert MTB/RIF-positive and 18 (17%) would not have tuberculosis (false-positives); 897 would be Xpert MTB/RIF-negative and 15 (2%) would have tuberculosis (false-negatives).Xpert Ultra sensitivity (95% confidence interval (CI)) was 88% (85% to 91%) versus Xpert MTB/RIF 83% (79% to 86%); Xpert Ultra specificity was 96% (94% to 97%) versus Xpert MTB/RIF 98% (97% to 99%), (1 study, 1439 participants; moderate-certainty evidence).Xpert MTB/RIF pooled sensitivity was 98% (97% to 98%) in smear-positive and 67% (62% to 72%) in smear-negative, culture-positive participants, (45 studies). Xpert MTB/RIF pooled sensitivity was 88% (83% to 92%) in HIV-negative and 81% (75% to 86%) in HIV-positive participants; specificities were similar 98% (97% to 99%), (14 studies).Rifampicin resistance detectionXpert MTB/RIF pooled sensitivity and specificity (95% Crl) were 96% (94% to 97%) and 98% (98% to 99%), (48 studies, 8020 participants; high-certainty evidence).For a population of 1000 people where 100 have rifampicin-resistant tuberculosis, 114 would be positive for rifampicin-resistant tuberculosis and 18 (16%) would not have rifampicin resistance (false-positives); 886 would be would be negative for rifampicin-resistant tuberculosis and four (0.4%) would have rifampicin resistance (false-negatives).Xpert Ultra sensitivity (95% CI) was 95% (90% to 98%) versus Xpert MTB/RIF 95% (91% to 98%); Xpert Ultra specificity was 98% (97% to 99%) versus Xpert MTB/RIF 98% (96% to 99%), (1 study, 551 participants; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

We found Xpert MTB/RIF to be sensitive and specific for diagnosing PTB and rifampicin resistance, consistent with findings reported previously. Xpert MTB/RIF was more sensitive for tuberculosis in smear-positive than smear-negative participants and HIV-negative than HIV-positive participants. Compared with Xpert MTB/RIF, Xpert Ultra had higher sensitivity and lower specificity for tuberculosis and similar sensitivity and specificity for rifampicin resistance (1 study). Xpert MTB/RIF and Xpert Ultra provide accurate results and can allow rapid initiation of treatment for multidrug-resistant tuberculosis.

[Respiratory isolation in suspected tuberculosis with negative direct sputum examination]

Airborne isolation is the main confinement measure used to limit human-to-human transmission of tuberculosis. If implemented early, precisely as soon as the patient is clinically diagnosed with tuberculosis, this measure will protect the population, particularly the health workers who are exposed. A patient suspected of being infected with tuberculosis can create a difficult situation if microbiological examination of his respiratory secretions is negative. This is a complex laboratory technique and sensitivity varies from one test to another. Thus, a false negative result is possible; meaning that a patient can have positive results on a microbiological culture performed later. This patient would still have low, but not no, contagiousness as long as a treatment has not been initiated. This situation can extend the period of respiratory isolation while further diagnostic investigations are carried out. This extended isolation can reduce the quality of health care delivered and patients can show signs of depression and anxiety. The use in routine clinical investigation of gene amplification tools should allow a rethinking of respiratory isolation rules. These tools, which are very sensitive and with a short reporting time, could drastically reduce the duration of respiratory isolation for patients suspected of being infected with tuberculosis.

Further evidence of Mycobacterium tuberculosis in the sputum of culture-negative pulmonary tuberculosis suspects using an ultrasensitive molecular assay

BACKGROUND

Rapid diagnosis of pulmonary tuberculosis (TB) is critical to TB control. However, many patients with paucibacillary TB disease remain undiagnosed. Current TB elimination goals require new tools to diagnose early disease. We evaluated performance of the Totally Optimized PCR (TOP) TB assay, a novel ultrasensitive molecular test.

METHODS

We assessed analytical specificity against nontuberculous mycobacteria (NTM), and estimated the diagnostic accuracy of TOP in a pilot study in Brazil (n = 46) and a cross-sectional study in Boston (n = 60). We compared TOP results to culture and a composite reference standard (CRS).

RESULTS

TOP exhibited no cross-reactivity against NTM. We tested 132 respiratory specimens from 106 patients with suspected pulmonary TB. The pilot demonstrated feasibility and 100% (95% CI 85-100) sensitivity in predominantly smear-positive specimens; TOP's specificity against solid media culture was low (58%, 37-77) but improved against a CRS (93%, 68-100). Similarly, when using the CRS in the Boston study, TOP (88%, 1-99) had greater sensitivity than solid or liquid media culture (25%, 3-65) and similar specificity (both 100%, 93-100).

CONCLUSIONS

The TOP assay enables detection of M. tuberculosis in culture-negative paucibacillary disease. While the use of TOP for the diagnosis of paucibacillary disease will require further clinical validation, its high sensitivity indicate a more immediate utility as a rule out TB test.

Current Medical Management of Pulmonary Tuberculosis

Tuberculosis (TB) remains a common cause of infection and disease in much of the world. The majority of disease occurs from reactivation months or years after initial infection and most often involves the lungs. Sputum smears for acid-fast bacilli remain the initial diagnostic test but have limited sensitivity and specificity. Nucleic acid amplification tests are more sensitive and specific and can detect some mutations that cause drug resistance. Treatment of TB resistant to rifamycins alone or in combination with isoniazid and other drugs remains difficult and should be done in consultation with an expert in treating drug-resistant disease.

Mycobacterial Infections in Patients With Chronic Kidney Disease and Kidney Transplantation

Patients with chronic kidney disease have impaired immunity that increases their risk of infection. Increased incidence of mycobacterial infections, in particular Mycobacterium tuberculosis, is described in patients undergoing hemodialysis and peritoneal dialysis as well as after kidney transplantation in low-prevalence and high-prevalence settings. Diagnosis of this infection can be challenging because of atypical presentations that may lead to treatment delay and, consequently, increased mortality; however, recent advances in molecular testing have improved diagnostic accuracy. It is imperative to try to identify those patients at increased risk and offer adequate prophylaxis. There are controversies and insufficient data regarding treatment agents, duration, and dosages. Most studies in nontuberculous mycobacteria are based on case series and retrospective studies.

Association of Rapid Molecular Testing With Duration of Respiratory Isolation for Patients With Possible Tuberculosis in a US Hospital

IMPORTANCE

New guidelines recommend that molecular testing replace sputum-smear microscopy to guide discontinuation of respiratory isolation in patients undergoing evaluation for active tuberculosis (TB) in health care settings.

OBJECTIVE

To evaluate the implementation and impact of a molecular testing strategy to guide discontinuation of isolation.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study with a pragmatic, before-and-after-implementation design of 621 consecutive patients hospitalized at Zuckerberg San Francisco General Hospital and Trauma Center who were undergoing sputum examination for evaluation for active pulmonary TB from January 2014 to January 2016.

INTERVENTIONS

Implementation of a sputum molecular testing algorithm using GeneXpert MTB/RIF (Xpert; Cepheid) to guide discontinuation of isolation.

MAIN OUTCOMES AND MEASURES

We measured the proportion of patients with molecular testing ordered and completed; the accuracy of the molecular testing algorithm in reference to mycobacterial culture; the duration of each component of the testing and isolation processes; length of stay; mean days in isolation and in hospital; and mean cost. We extracted data from hospital records and compared measures before and after implementation.

RESULTS

Clinicians ordered sputum testing for TB for 621 patients at ZSFG during the 2-year study period. Of 301 patients in the preimplementation period with at least 1 sputum microscopy and culture ordered, clinicians completed the rapid TB testing evaluation process for 233 (77%).Among 320 patients evaluated in the postimplementation period, clinicians ordered molecular testing for 234 (73%) patients and received results for 295 of 302 (98%) tests ordered. Median age was 54 years (interquartile range, 44-63 years), and 161 (26%) were women. The molecular testing algorithm accurately diagnosed all 7 patients with culture-confirmed TB and excluded TB in all 251 patients with Mycobacterium tuberculosis (MTB) culture-negative results. Compared with the preimplementation period, there were significant decreases in median times to final rapid test result (39.1 vs 22.4 hours, P < .001), discontinuation of isolation (2.9 vs 2.5 days, P = .001), and hospital discharge (6.0 vs 4.9 days, P = .003), on average saving $13 347 per isolated TB-negative patient.

CONCLUSIONS AND RELEVANCE

A sputum molecular testing algorithm to guide discontinuation of respiratory isolation for patients undergoing evaluation for active TB was safe, feasible, widely and sustainably adopted, and provided substantial clinical and economic benefits. Molecular testing may facilitate more efficient, patient-centered evaluation for possible TB in US hospitals.

New and Noteworthy in Tuberculosis Diagnostics and Treatment

People with HIV infection with latent tuberculosis (TB) infection (LTBI) are at a 10-fold greater risk of developing active disease. Interferon gamma release assays and tuberculin skin testing have approximately 65% to 70% specificity for diagnosing LTBI in HIV-infected patients. LTBI can be successfully treated with isoniazid preventive therapy and early antiretroviral therapy (ART). Rapid molecular diagnostics have approximately 88% sensitivity and 98% specificity for identifying active TB. ART should be started early in patients with TB. A number of ART regimens are recommended in co-treatment that minimize the risk of drug-drug interactions. Although progress has been made, better diagnostics and TB regimens with lower risks of drug-drug interactions and shorter treatment durations are still needed. This article summarizes a presentation by Susan Swindells, MBBS, at the Ryan White HIV/AIDS Program Clinical Care Conference held in San Antonio in August 2017.

Rapid molecular assays for detection of tuberculosis

Tuberculosis (TB) is an infectious disease that remains an important public health problem at the global level. It is one of the main causes of morbidity and mortality, due to the emergence of antibiotic resistant Mycobacterium strains and HIV co-infection. Over the past decade, important progress has been made for better control of the disease. While microscopy and culture continue to be indispensible for laboratory diagnosis of tuberculosis, the range of several molecular diagnostic tests, including the nucleic acid amplification test (NAAT) and whole-genome sequencing (WGS), have expanded tremendously. They are becoming more accessible not only for detection and identification of Mycobacterium tuberculosis complex in clinical specimens, but now extend to diagnosing multi-drug resistant strains. Molecular diagnostic tests provide timely results useful for high-quality patient care, low contamination risk, and ease of performance and speed. This review focuses on the current diagnostic tests in use, including emerging technologies used for detection of tuberculosis in clinical specimens. The sensitivity and specificity of these tests have also been taken into consideration.

The role of the Xpert MTB/RIF assay among adolescents suspected of pulmonary tuberculosis in Rio de Janeiro, Brazil

INTRODUCTION

The teste rápido molecular para tuberculose (TRM-TB) was introduced in 2014 in Brazil for tuberculosis screening. However, its role in adolescents in Brazil has not been studied.

METHODS

A descriptive study of adolescents with suspected tuberculosis using National Laboratory software.

RESULTS

Of 852 (15.4%) suspected cases, 131 were positive by TRM-TB and 2% were resistant to rifampicin. Among TRM-TB-positive cases, 105 (91.4%) were culture-positive. Sixty-four of 96 samples were sensitive to rifampicin by TRM-TB; 11 were resistant to other drugs by drug sensitivity test (DST).

CONCLUSIONS

Among suspected cases, 16% were diagnosed by TRM-TB, of which 17% were drug-resistant by DST.

Performance of a Highly Sensitive Mycobacterium tuberculosis Complex Real-Time PCR Assay for Diagnosis of Pulmonary Tuberculosis in a Low-Prevalence Setting: a Prospective Intervention Study

The potential impact of routine real-time PCR testing of respiratory specimens from patients with presumptive tuberculosis in terms of diagnostic accuracy and time to tuberculosis treatment inception in low-prevalence settings remains largely unexplored. We conducted a prospective intervention cohort study. Respiratory specimens from 1,020 patients were examined by acid-fast bacillus smear microscopy, tested by a real-time Mycobacterium tuberculosis complex PCR assay (Abbott RealTime MTB PCR), and cultured in mycobacterial media. Seventeen patients tested positive by PCR (5 were acid-fast bacillus smear positive and 12 acid-fast bacillus smear negative), and Mycobacterium tuberculosis was recovered from cultures for 12 of them. Patients testing positive by PCR and negative by culture (n = 5) were treated and deemed to have responded to antituberculosis therapy. There were no PCR-negative/culture-positive cases, and none of the patients testing positive for nontuberculous mycobacteria (n = 20) yielded a positive PCR result. The data indicated that routine testing of respiratory specimens from patients with presumptive tuberculosis by the RealTime MTB PCR assay improves the tuberculosis diagnostic yield and may reduce the time to antituberculosis treatment initiation. On the basis of our data, we propose a novel mycobacterial laboratory algorithm for tuberculosis diagnosis.

Use of a Single Xpert MTB/RIF Assay to Determine the Duration of Airborne Isolation in Hospitalized Patients With Suspected Pulmonary Tuberculosis

BACKGROUNDHospitalized patients with suspected tuberculosis (TB) are placed in airborne isolation until 3 sputum smear samples are negative for acid-fast bacilli (AFB). The Xpert MTB/RIF assay ("Xpert") nucleic acid amplification test (NAAT) to identify Mycobacterium tuberculosis DNA and resistance to rifampicin is superior to AFB sputum smear microscopy for the diagnosis of TB.OBJECTIVETo compare the performance of a single Xpert to AFB smear microscopy for time to airborne infection isolation (AII) discontinuation.METHODSConsecutive patients over 17 years of age in AII for suspected pulmonary TB between October 1, 2014, and March 31, 2016, with leftover respiratory AFB samples were enrolled in this study. A single Xpert was performed on the first available sample. Demographic, clinical, and microbiological data were recorded for each patient. We compared the duration of AII using a single Xpert to AFB smear microscopy under multiple theoretical scenarios using Kaplan-Meier cumulative incidence curves and the log-rank test.RESULTSIn total, 131 samples were included in our performance analysis of the Xpert, and 114 samples were included in our AII analysis. Overall, 81 patients (65%) were immunosuppressed, of whom 46 (37%) were positive for human immunodeficiency virus (HIV). The sensitivity and specificity of Xpert for diagnosis of M. tuberculosis infection were 67% and 100%, respectively. Xpert was negative in all cases of nontuberculous mycobacteria. Use of a single Xpert reduced AII duration from a median of 67 hours per patient to 42 hours with usual reporting, to 26 hours with direct communication, and to 12 hours with immediate testing.CONCLUSIONSA single negative Xpert result can reduce AII duration compared to the AFB smear microscopy technique under multiple theoretical scenarios.Infect Control Hosp Epidemiol 2018;39:590-595.

A Comprehensive Evaluation of Xpert MTB/RIF Assay With Bronchoalveolar Lavage Fluid as a Single Test or Combined With Conventional Assays for Diagnosis of Pulmonary Tuberculosis in China: A Two-Center Prospective Study

Introduction: The Xpert MTB/RIF is recommended by the World Health Organization as a first line rapid test for the diagnosis of pulmonary tuberculosis (TB); however, China does not routinely use this test, partially due to the lack of a sufficient number of systematic evaluations of this assay in local patients. The aims of this study were to comprehensively assess the diagnostic performance of Xpert MTB/RIF, either alone or in combination with conventional assays for the diagnosis of pulmonary TB in adult Chinese patients. Methods: Xpert MTB/RIF tests were performed in 190 adult patients with suspected pulmonary TB, using bronchoalveolar lavage fluid (BALF) as test specimens. In parallel, conventional tests were carried out using the same BALF samples. Using two different reference standards, the performance of Xpert MTB/RIF, conventional assays and their combinations were evaluated. Results: Using mycobacterial culture as the reference comparator, Xpert MTB/RIF was found to be superior to smear-microscopy in detecting Mycobacterium tuberculosis. When final diagnosis, based on clinical criteria, was employed as the reference standard, Xpert MTB/RIF showed an even higher accuracy of 72.1%, supported by a sensitivity of 61.1% and specificity of 96.6%. Xpert MTB/RIF also demonstrated a powerful capability to identify pulmonary TB cases undetected by culture or smear-microscopy. Combining smear-microscopy and Xpert MTB/RIF was found to be the most accurate early predictor for pulmonary TB. Rifampicin resistance reported by Xpert MTB/RIF slightly deviated from that by phenotypic antibiotic susceptibility testing and requires further study with a larger sample size. Conclusion: This two-center prospective study highlights the value of Xpert MTB/RIF with BALF in diagnosing pulmonary TB in adult Chinese patients. These findings might contribute to the optimization of current diagnostic algorithms for pulmonary TB in China.

Cough Due to TB and Other Chronic Infections: CHEST Guideline and Expert Panel Report

BACKGROUND

Cough is common in pulmonary TB and other chronic respiratory infections. Identifying features that predict whether pulmonary TB is the cause would help target appropriate individuals for rapid and cost-effective screening, potentially limiting disease progression and preventing transmission to others.

METHODS

A systematic literature search for individual studies to answer eight key questions (KQs) was conducted according to established Chest Organization methods by using the following databases: MEDLINE via PubMed, Embase, Scopus, and the Cochrane Database of Systematic Reviews from January 1, 1984, to April 2014. Searches for KQ 1 and KQ 3 were updated in February 2016. An updated KQ 2 search was undertaken in March 2017.

RESULTS

Even where TB prevalence is greatest, most individuals with cough do not have pulmonary TB. There was no evidence that 1, 3, or 4 weeks' duration were better predictors than cough lasting ≥ 2 weeks to screen for pulmonary TB. In people living with HIV (PLWHIV), screening for fever, night sweats, hemoptysis, and/or weight loss in addition to cough (any World Health Organization [WHO]-endorsed symptom) increases the diagnostic sensitivity for TB. Although the diagnostic accuracy of symptom-based screening remains low, the negative predictive value of the WHO-endorsed symptom screen in PLWHIV may help to risk-stratify individuals who are not close TB contacts and who do not require further testing for pulmonary TB in resource-limited settings. However, pregnant PLWHIV are more likely to be asymptomatic, and the WHO-endorsed symptom screen is not sensitive enough to be reliable. Combined with passive case finding (PCF), active case finding (ACF) identifies pulmonary TB cases earlier and possibly when less advanced. Whether outcomes are improved or transmission is reduced is unclear. Screening asymptomatic patients is cost-effective only in populations with a very high TB prevalence. The Xpert MTB/RIF assay on sputum is more cost-effective than clinical diagnosis. To our knowledge, no published comparative studies addressed whether the rate of cough resolution is a reliable determinant of the response to treatment or whether the rate of cough resolution was faster in the absence of cavitary lung disease. All studies on cough prevalence in Mycobacterium avium complex (MAC) lung disease, other nontuberculous mycobacterial infections, fungal lung disease, and paragonimiasis were of poor quality and were excluded from the evidence review.

CONCLUSIONS

On the basis of relatively few studies of fair to good quality, we conclude that most individuals at high risk and household contacts with cough ≥ 2 weeks do not have pulmonary TB, but we suggest screening them regardless of cough duration. In PLWHIV, the addition of the other WHO-endorsed symptoms increases the diagnostic sensitivity of cough. Earlier screening of patients with cough will help diagnose pulmonary TB sooner but will increase the cost of screening. The addition of ACF to PCF will increase the number of pulmonary TB cases identified. Screening asymptomatic individuals is cost-effective only in groups with a very high TB prevalence. Data are insufficient to determine whether cough resolution is delayed in individuals with cavitary lung disease or in those for whom treatment fails because of drug resistance, poor adherence, and/or drug malabsorption compared with results in other individuals with pulmonary TB. Cough is common in patients with lung infections due to MAC, other nontuberculous mycobacteria, fungal diseases, and paragonimiasis.

Practice Guidelines for Clinical Microbiology Laboratories: Mycobacteria

Mycobacteria are the causative organisms for diseases such as tuberculosis (TB), leprosy, Buruli ulcer, and pulmonary nontuberculous mycobacterial disease, to name the most important ones. In 2015, globally, almost 10 million people developed TB, and almost half a million patients suffered from its multidrug-resistant form. In 2016, a total of 9,287 new TB cases were reported in the United States. In 2015, there were 174,608 new case of leprosy worldwide. India, Brazil, and Indonesia reported the most leprosy cases. In 2015, the World Health Organization reported 2,037 new cases of Buruli ulcer, with most cases being reported in Africa. Pulmonary nontuberculous mycobacterial disease is an emerging public health challenge. The U.S. National Institutes of Health reported an increase from 20 to 47 cases/100,000 persons (or 8.2% per year) of pulmonary nontuberculous mycobacterial disease among adults aged 65 years or older throughout the United States, with 181,037 national annual cases estimated in 2014. This review describes contemporary methods for the laboratory diagnosis of mycobacterial diseases. Furthermore, the review considers the ever-changing health care delivery system and stresses the laboratory's need to adjust and embrace molecular technologies to provide shorter turnaround times and a higher quality of care for the patients who we serve.