Impact of GeneXpert MTB/RIF assay on triage of respiratory isolation rooms for inpatients with presumed tuberculosis: a hypothetical trial

Second Time's the Charm? Assessing the Sensitivity and Yield of Inpatient Diagnostic Algorithms for Pulmonary Tuberculosis in a Low-Prevalence Setting

Background

For persons with suspected pulmonary tuberculosis, the guidelines of the Centers for Disease Control and Prevention recommend collecting 3 respiratory specimens 8 to 24 hours apart for acid-fast bacilli (AFB) smear and culture, in addition to 1 nucleic acid amplification test (NAAT). However, data supporting this approach are limited. Our objective was to estimate the performance of 1, 2, or 3 AFB smears with or without NAATs to detect pulmonary tuberculosis in a low-prevalence setting.

Methods

We conducted a retrospective study of hospitalized persons at 8 Massachusetts acute care facilities who underwent mycobacterial culture on 1 or more respiratory specimens between July 2016 and December 2022. We evaluated percentage positivity and yield on serial AFB smears and NAATs among people with growth of Mycobacterium tuberculosis on mycobacterial cultures.

Results

Among 104 participants with culture-confirmed pulmonary tuberculosis, the first AFB smear was positive in 41 cases (39%). A second AFB smear was positive in 11 (22%) of the 49 cases in which it was performed. No third AFB smears were positive following 2 initial negative smears. Of 52 smear-negative cases, 36 had a NAAT performed, leading to 23 additional diagnoses. Overall sensitivity to detect tuberculosis prior to culture positivity was higher in any strategy involving 1 or 2 NAATs (74%-79%), even without AFB smears, as compared with 3 smears alone (60%).

Conclusions

Tuberculosis diagnostic testing with 2 AFB smears offered the same yield as 3 AFB smears while potentially reducing laboratory burden and duration of airborne infection isolation. Use of 1 or 2 NAATs increased sensitivity to detect culture-positive pulmonary tuberculosis when added to AFB smear-based diagnostic testing alone.

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.

Usefulness of Mycobacterium tuberculosis-polymerase chain reaction with bronchial washing samples in predicting discontinuation of airborne infection isolation in patients hospitalized with suspected pulmonary tuberculosis

OBJECTIVE

In-hospital tuberculosis (TB) transmission remains a concern. Airborne infection isolation (AII) can be discontinued in hospitalized patients with suspected active pulmonary TB when the results of three consecutive sputum acid-fast bacilli (AFB) smears are negative. However, fiberoptic bronchoscopy can be performed in patients who may have difficulty in producing sputum samples. This study aimed to investigate the usefulness of Mycobacterium tuberculosis-polymerase chain reaction (MTB-PCR) with bronchial washing specimens in predicting AII discontinuation in hospitalized patients with suspected active pulmonary TB.

METHODS

We reviewed the medical charts of patients admitted to a tertiary hospital who were isolated and underwent fiberoptic bronchoscopy for suspicious pulmonary TB from January 2016 to December 2019. Patients with positive MTB-PCR results in the initial sputum examination were excluded. Criteria for discontinuing AII were defined as negative results for three consecutive AFB smears from respiratory specimens, or cases diagnosed other than TB. The study patients were divided into two groups: TB group and non-TB group.

RESULTS

In total, 166 patients were enrolled in the study. Of them, 35 patients were diagnosed with TB. There was no significant difference between the number of males in the TB (81; 61.8%) and non-TB (21; 60.0%) group. Though 139 patients had negative results on MTB-PCR using washing specimens, eight showed positive AFB culture. Of the 139 patients with negative MTB-PCR results, 138 had negative results for three consecutive AFB smears or were established to not have pulmonary TB. Therefore, the predictive accuracy of MTB-PCR with bronchial washing samples for discontinuing AII was 99.2%.

CONCLUSION

Although a negative result from MTB-PCR with bronchial washing samples cannot exclude pulmonary TB, it can predict AII discontinuation in hospitalized patients with suspected active pulmonary TB.

Impact of molecular diagnostic tests on diagnostic and treatment delays in tuberculosis: a systematic review and meta-analysis

BACKGROUND

Countries with high TB burden have expanded access to molecular diagnostic tests. However, their impact on reducing delays in TB diagnosis and treatment has not been assessed. Our primary aim was to summarize the quantitative evidence on the impact of nucleic acid amplification tests (NAAT) on diagnostic and treatment delays compared to that of the standard of care for drug-sensitive and drug-resistant tuberculosis (DS-TB and DR-TB).

METHODS

We searched MEDLINE, EMBASE, Web of Science, and the Global Health databases (from their inception to October 12, 2020) and extracted time delay data for each test. We then analysed the diagnostic and treatment initiation delay separately for DS-TB and DR-TB by comparing smear vs Xpert for DS-TB and culture drug sensitivity testing (DST) vs line probe assay (LPA) for DR-TB. We conducted random effects meta-analyses of differences of the medians to quantify the difference in diagnostic and treatment initiation delay, and we investigated heterogeneity in effect estimates based on the period the test was used in, empiric treatment rate, HIV prevalence, healthcare level, and study design. We also evaluated methodological differences in assessing time delays.

RESULTS

A total of 45 studies were included in this review (DS = 26; DR = 20). We found considerable heterogeneity in the definition and reporting of time delays across the studies. For DS-TB, the use of Xpert reduced diagnostic delay by 1.79 days (95% CI - 0.27 to 3.85) and treatment initiation delay by 2.55 days (95% CI 0.54-4.56) in comparison to sputum microscopy. For DR-TB, use of LPAs reduced diagnostic delay by 40.09 days (95% CI 26.82-53.37) and treatment initiation delay by 45.32 days (95% CI 30.27-60.37) in comparison to any culture DST methods.

CONCLUSIONS

Our findings indicate that the use of World Health Organization recommended diagnostics for TB reduced delays in diagnosing and initiating TB treatment. Future studies evaluating performance and impact of diagnostics should consider reporting time delay estimates based on the standardized reporting framework.

The Value of GeneXpert MTB/RIF for Detection in Tuberculosis: A Bibliometrics-Based Analysis and Review

With the continuous development of medical science and technology, especially with the advent of the era of precision diagnosis and treatment, molecular biology detection technology is widely valued and applied as an aid to early diagnosis of tuberculosis. The GeneXpert Mycobacterium tuberculosis Branching (MTB) technology is a suite of semi-nested real-time fluorescent quantitative PCR in vitro diagnostic technologies developed by Cepheid Inc. It targets the rifampicin resistance gene, rpoB, and can detect both MTB and resistance to rifampicin within 2 h. This review analyzed the papers related to GeneXpert using bibliometric software CiteSpace and Bibliometrix. A total of 151 articles were analyzed, spanning from 2011 to 2021. This bibliometrics-based review summarizes the history of the development of GeneXpert in tuberculosis diagnosis and its current status. Contributions of different countries to the topic, journal analysis, key paper analysis, and clustering of keywords were used to analyze this topic.

Diagnostic Performance of Xpert MTB/RIF Ultra Compared with Predecessor Test, Xpert MTB/RIF, in a Low TB Incidence Setting: a Retrospective Service Evaluation

The aim of this study was to evaluate the performance of Xpert MTB/RIF Ultra (Ultra) compared with its predecessor, Xpert MTB/RIF (Xpert), in the diagnosis of tuberculosis (TB) in a low TB incidence country. Retrospective analysis was performed on 689 clinical samples received between 2015 and 2018, on which Xpert was performed, and on 715 samples, received between 2018 and 2020, on which Ultra was performed. Samples were pulmonary (n = 830) and extrapulmonary (n = 574) in nature, and a total of 264 were culture positive for Mycobacterium tuberculosis complex (MTBC). The diagnostic performance of both assays was analyzed using culture as the reference standard. The sensitivity of Ultra for culture positive (smear positive and smear negative) MTBC samples, was 93.2% (110/118) compared with 82.2% (120/146) for Xpert (P = 0.0078). In smear negative-culture positive samples, Ultra had a sensitivity of 74.2% (23/31) versus 36.11% (13/36) for Xpert (P = 0.0018). Specificity of both assays was comparable at 94.8% (566/597) for Ultra and 95.8% (520/543) for Xpert (P = 0.4475). The sensitivity of Ultra and Xpert assays among exclusively pulmonary samples was 95.3% (82/86) and 90.3% (84/93), respectively (P = 0.1955), and 87.5% (28/32) and 67.9% (36/53), respectively, among extrapulmonary samples (P = 0.0426). Ultra showed improved performance compared with Xpert in a low TB incidence setting, particularly in smear negative and extrapulmonary MTBC disease. The specificity of Ultra was lower than Xpert, however, this was not statistically significant. IMPORTANCE The study demonstrates the improved sensitivity of the Ultra compared with the Xpert, particularly in smear negative TB disease, for both pulmonary and extrapulmonary samples in a low TB incidence setting. Cycle threshold (Ct) value for both assays was found to positively correlate with time to TB culture positivity, suggesting that Ct and semiquantitative results could be used as indicators of sample MTBC bacillary burden, and thus, perhaps, of transmission potential. This may have implications for the designation of patient isolation precautions.

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.

The impact of the Xpert MTB/RIF screening among hospitalized patients with pneumonia on timely isolation of patients with pulmonary tuberculosis

In South Korea where the tuberculosis (TB) burden is intermediate, the risk of in-hospital transmission of TB remains high. We conducted a retrospective cohort study of 244 inpatients diagnosed with pulmonary TB (2015–2018) to evaluate the impact of the Xpert MTB/RIF assay (Xpert) screening on timely isolation. TB screening was performed with smear microscopy and a polymerase chain reaction test, and the Xpert was additionally used from November 2016. Among all patients with pulmonary TB, the median time-to-isolation was significantly reduced (22.6 vs. 69.7 h; p < 0.001) and segmented regression analysis adjusting for the time trend showed a reduction in time-to-isolation with the introduction of the Xpert (− 39.3 h; 95% CI − 85.6, 7.0; p = 0.096). Among 213 patients who were timely screened (≤ 72 h after admission), time-to-isolation decreased significantly (− 38.2 h; 95% CI − 70.6, − 5.8; p = 0.021) with the introduction of the Xpert, and its decreasing trend continued. The Xpert provided a shorter turnaround time (4.8 vs. 49.1 h; p < 0.001) and higher sensitivity (76.6% vs. 47.8%; p < 0.001) than smear microscopy. Thus, the Xpert can be a useful screening test for pulmonary TB in real-life hospital settings with an intermediate TB burden.

Rapid detection of tuberculosis in remote Alaska

In a remote region of western Alaska where tuberculosis (TB) incidence remains relatively high, a rapid molecular detection assay (Xpert MTB/RIF) was introduced four years ago with goal of improving the ability to diagnose active pulmonary tuberculosis (TB).  Our aggressive testing programme was intended for all patients acutely evaluated for pulmonary TB at our regional hospital and multiple clinics over a large area. All 223 consecutive patients evaluated for active pulmonary TB were tested with Xpert MTB/RIF (Xpert) per our protocol of which 192 (86.1%) had at least one additional (paired) sputum sample collected for standard acid-fast bacilli (smear) microscopy and culture. Fourteen patients eventually became culture-positive for Mycobacterium tuberculosis (MTB), all but one having initially tested positive (MTB detected) by Xpert (sensitivity 92.9%). All remaining culture-negative individuals had tested negative (not detected) by Xpert (specificity 100%). By contrast, smear microscopy sensitivity and specificity was 64.3% and 98.9% respectively.  This represents the addition of four active TB patients detected by Xpert over smear. In remote regions, the ability of Xpert to quickly and reliably detect TB while determine which patients are not contagious represents a huge healthcare savings as in most cases these patients will not require hospitalized isolation.

Cost analysis of smear microscopy and the Xpert assay for tuberculosis diagnosis: average turnaround time

INTRODUCTION

Rapid and accurate tuberculosis detection is critical for improving patient diagnosis and decreasing tuberculosis transmission. Molecular assays can significantly increase laboratory costs; therefore, the average time and economic impact should be evaluated before implementing a new technology. The aim of this study was to evaluate the cost and average turnaround time of smear microscopy and Xpert assay at a university hospital.

METHODS

The turnaround time and cost of the laboratory diagnosis of tuberculosis were calculated based on the mean cost and activity based costing (ABC).

RESULTS

The average turnaround time for smear microscopy was 16.6 hours while that for Xpert was 24.1 hours. The Xpert had a mean cost of USD 17.37 with an ABC of USD 10.86, while smear microscopy had a mean cost of USD 13.31 with an ABC of USD 6.01. The sensitivity of smear microscopy was 42.9% and its specificity was 99.1%, while the Xpert assay had a sensitivity of 100% and a specificity of 96.7%.

CONCLUSIONS

The Xpert assay has high accuracy; however, the turnaround time and cost of smear microscopy were lower than those of Xpert.

Point-of-Care Testing in Microbiology: A Mechanism for Improving Patient Outcomes

BACKGROUND

Increasingly, demands for improved health and quality of life conflict with the realities of delivering healthcare in an environment of higher expenditures, adherence to test utilization, and patient-centered experience. Patient-centered care is commonly identified as a goal of healthcare delivery, and yet healthcare systems struggle with delivery of care to patients, often failing to identify the seriously ill and capitalize on the predictive qualities of diagnostic testing. Point-of-care (POC) testing provides access to rapid diagnosis and predictive value key to realizing patient outcomes. An evaluation of cost-effective models and the clinical impact of POC testing for clinical microbiology is needed.

CONTENT

Accurate and rapid diagnostics have the potential to affect healthcare decisions to a degree well out of proportion to their cost. Contemporary healthcare models increasingly view POC testing as a mechanism for efficient deployment of healthcare. POC testing can deliver rapid diagnosis in environments where testing results can be used to direct management during patient visits and in areas where centralized laboratory testing may limit access to care. Nucleic acid assays, designed for POC testing, can match, or exceed, the sensitivity of conventional laboratory-based testing, eliminating the need for confirmation testing. Here, the goals of POC testing for microbiology, applications, and technologies, as well as outcomes and value propositions, are discussed.

SUMMARY

The combination of rapid reporting, an increasing array of organisms capable of causing disease, actionable resulting, and improved patient outcomes is key in the evolution of POC testing in clinical microbiology.

Decision making to discharge patients from airborne infection isolation rooms: The role of a single GeneXpert MTB/RIF strategy in Brazil

OBJECTIVE

Tuberculosis (TB) transmission in healthcare facilities is still a concern in low-income countries, where airborne isolation rooms are scarce due to high costs. We evaluated the use of single GeneXpert MTB/RIF, the molecular Mycobacterium tuberculosis (MTB) DNA and resistance to rifampicin (RIF) test, as an accurate and faster alternative to the current criteria of 3 negative acid-fast bacilli (AFB) smears to remove patients from airborne isolation.

METHODS

In this real-world investigation, we evaluated the impact of a single GeneXpert MTB/RIF on the decision making for discharging patients from respiratory isolation. We enrolled patients with suspected pulmonary TB in a public hospital that provides care for high-complexity patients in Brazil. We studied the performance, costs, and time saved comparing the GeneXpert MTB/RIF with AFB smears.

RESULTS

We enrolled 644 patients in 3 groups based on the number of AFB smears performed (1, 2, and 3, respectively) on respiratory specimens. GeneXpert MTB/RIF demonstrated good performance compared to AFB smear to rule out TB in all groups. The negative predictive value for AFB smear was 94% (95% confidence interval [CI], 0.90-0.97) and 98% (95% CIs, 0.94-0.99) for GeneXpert MTB/RIF in G3. The isolation discharge based on 3 AFB smears took 84 hours compared to 24 hours with GeneXpert MTB/RIF, which represents 560 patient-days saved in the isolation rooms.

CONCLUSION

A single GeneXpert MTB/RIF is a fast and strong predictor for TB absence in a high-complexity hospital, which is quite similar to results obtained in recent studies in low-burden settings. This molecular test may also increase patient rotation through isolation rooms, with a positive impact in the emergency room and infectious diseases wards.

Isolation and deisolation of patients admitted with presumptive pulmonary tuberculosis. Can it be shortened?

Objectives:

To determine the ideal number of sputum acid-fast bacilli (AFB) smears and polymerase chain reaction (PCR) required for discontinuing tuberculosis (TB) isolation among patients with suspected pulmonary TB.

Methods:

This was a single-center, record-based retrospective study of all admitted patients diagnosed with culture-proven pulmonary TB between 2010 and 2018. The study was conducted at Prince Sultan Military Medical City (PSMMC) in Riyadh, Saudi Arabia, a large tertiary care center consisting of 1,200 beds. Data were obtained from our TB notification records. Patients with smear-positive TB were investigated. Only the first 3 sputum smears for AFB were included in the analysis. The PCR results for Mycobacterium tuberculosis (MTB) were also included in the study. The incremental yield of the second and third smears was assessed.

Results:

Overall, 240 patients were MTB-culture positive. A total of 126 (52.5%) patients were smear and culture positive, whereas 114 were culture positive but smear negative. Of 126 patients who were AFB smear positive, 98 (77.8%) were detected in the first specimen, 13 (10.3%) in the second specimen, and only 9 (7.1%) in the third specimen. Polymerase chain reaction for MTB was positive in 122 (96.8%) smear-positive patients. Four patients did not undergo a PCR test.

Conclusion:

A single Xpert MTB/resistance to rifampicin test detected all smear-positive patients, whereas the third smear did not significantly contribute to MTB isolation.

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 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.

Performance of diagnostic tests for pulmonary tuberculosis in indigenous populations in Brazil: the contribution of Rapid Molecular Testing

OBJECTIVE

To evaluate the accuracy of rapid molecular testing as a diagnostic tool and estimate the incidence of smear-positive pulmonary tuberculosis among the indigenous population.

METHODS

This is an epidemiological study based on secondary data. We calculated the incidence of smear-positive pulmonary tuberculosis between January 1st, 2011 and December 31, 2016, and the performance of bacilloscopy and rapid molecular testing in diagnosing pulmonary tuberculosis compared to sputum culture (standard test).

RESULTS

We included 4,048 cases of indigenous people with respiratory symptoms who provided sputum samples for analysis. Among them, 3.7%, 6.7%, and 3.7% had positive results for bacilloscopy, sputum culture, and rapid molecular testing, respectively. The mean incidence of pulmonary tuberculosis was 269.3/100 thousand inhabitants. Rapid molecular testing had 93.1% sensitivity and 98.2% specificity, compared to sputum culture. Bacilloscopy showed 55.1% sensitivity and 99.6% specificity.

CONCLUSIONS

Rapid molecular testing can be useful in remote areas with limited resources and a high incidence of tuberculosis, such as indigenous villages in rural regions of Brazil. In addition, the main advantages of rapid molecular testing are its easy handling, fast results, and the possibility of detecting rifampicin resistance. Together, these attributes enable the early start of treatment, contributing to reduce the transmission in communities recognized as vulnerable to infection and disease.

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.

Molecular Diagnostics for Mycobacterium tuberculosis Infection

Resistance to antimycobacterial drugs is a major barrier to effective treatment of Mycobacterium tuberculosis infection. Molecular diagnostic techniques based on the association between specific gene mutations and phenotypic resistance to certain drugs offer the opportunity to rapidly ascertain whether drug resistance is present and to alter treatment before further resistance develops. Current barriers to successful implementation of rapid diagnostics include imperfect knowledge regarding the full spectrum of mutations associated with resistance, limited utilization of molecular diagnostics where they are most needed, and the requirement for specialized laboratory facilities to perform molecular testing. Further understanding of genotypic-phenotypic correlates of resistance and streamlined implementation platforms will be necessary to optimize the public health impact of molecular resistance testing for M. tuberculosis.

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.

Estimation of discrete survival function for error-prone diagnostic tests

The product limit or Kaplan-Meier (KM) estimator is commonly used to estimate the survival function in the presence of incomplete time to event. Application of this method assumes inherently that the occurrence of an event is known with certainty. However, the clinical diagnosis of an event is often subject to misclassification due to assay error or adjudication error, by which the event is assessed with some uncertainty. In the presence of such errors, the true distribution of the time to first event would not be estimated accurately using the KM method. We develop a method to estimate the true survival distribution by incorporating negative predictive values and positive predictive values, into a KM-like method of estimation. This allows us to quantify the bias in the KM survival estimates due to the presence of misclassified events in the observed data. We present an unbiased estimator of the true survival function and its variance. Asymptotic properties of the proposed estimators are provided, and these properties are examined through simulations. We demonstrate our methods using data from the Viral Resistance to Antiviral Therapy of Hepatitis C study.

Clinical Impact and Cost-effectiveness of Xpert MTB/RIF Testing in Hospitalized Patients With Presumptive Pulmonary Tuberculosis in the United States

Background

Microscopic examination of acid-fast-stained sputum smears is the current standard of care in the United States to determine airborne infection isolation (AII) of inpatients with presumptive pulmonary tuberculosis (PTB). However, nucleic acid amplification testing (NAAT) with the Xpert MTB/RIF assay (Xpert) may be more efficient and less costly.

Methods

This prospective observational cohort study enrolled a consecutive sample of 318 AII-eligible inpatients from a public hospital in Seattle, Washington, from March 2012 to October 2013. Sputum samples were collected from each inpatient and analyzed using smear microscopy, culture, drug susceptibility testing, and NAAT. The performance, clinical utility (AII duration and survival), and cost-effectiveness from an institutional perspective were compared for 5 testing strategies.

Results

Among the 318 admissions with presumptive PTB, 20 (6.3%) were culture-positive for Mycobacterium tuberculosis. The sensitivity of 1 Xpert, 2 Xperts, 2 smears, or 3 smears compared to culture was 0.85 (95% confidence interval [CI], .61–.96), 0.95 (95% CI, .73–1.0), 0.70 (95% CI, .46–.88), and 0.80 (95% CI, .56–.93), respectively. A cost-effectiveness analysis of the study results demonstrated that an Xpert test on 1 unconcentrated sputum sample (assuming equivalent results for unconcentrated and concentrated sputum samples) is the most cost-effective strategy (99.9% preferred at willingness-to-pay of US$50000) and on average would save 51.5 patient-hours in AII and up to $11466 relative to microscopy without a compromise in sensitivity.

Conclusions

In hospitalized patients with presumptive PTB in a low-burden setting, NAAT can reduce AII and is comparably sensitive, more specific, and more cost-effective than smear microscopy.

Impact of the GeneXpert MTB/RIF Technology on Tuberculosis Control

Molecular technology revolutionized the diagnosis of tuberculosis (TB) with a paradigm shift to faster, more sensitive, clinically relevant patient care. The most recent molecular leader is the GeneXpert MTB/RIF assay (Xpert) (Cepheid, Sunnyvale, CA), which was endorsed by the World Health Organization with unprecedented speed in December 2010 as the initial diagnostic for detection of HIV-associated TB and for where high rates of drug resistance are suspected. South Africa elected to take an aggressive smear replacement approach to facilitate earlier diagnosis and treatment through the decision to implement the Xpert assay nationally in March 2011, against the backdrop of approximately 6.3 million HIV-infected individuals, one of highest global TB and HIV coinfection rates, no available implementation models, uncertainties around field performance and program costs, and lack of guidance on how to operationalize the assay into existing complex clinical algorithms. South Africa's national implementation was conducted as a phased, forecasted, and managed approach (March 2011 to September 2013), through political will and both treasury-funded and donor-funded support. Today there are 314 GeneXperts across 207 microscopy centers; over 8 million assays have been conducted, and South Africa accounts for over half the global test cartridge usage. As with any implementation of new technology, challenges were encountered, both predicted and unexpected. This chapter discusses the challenges and consequences of such large-scale implementation efforts, the opportunities for new innovations, and the need to strengthen health systems, as well as the impact of the Xpert assay on rifampin-sensitive and multidrug-resistant TB patient care that translated into global TB control as we move toward the sustainable development goals.

Use of Nucleic Acid Amplification Tests in Tuberculosis Patients in California, 2010-2013

BACKGROUND

Nucleic acid amplification tests (NAATs) have been used as a diagnostic tool for tuberculosis (TB) in the United States for many years. We sought to assess NAAT use in TB patients in California during a period of time when NAAT availability increased throughout the world.

METHODS

We conducted a retrospective review of surveillance data from 6051 patients with culture-confirmed pulmonary TB who were reported to the California TB registry during 2010-2013.

RESULTS

Only 2336 of 6051 (39%) TB patients had a NAAT for diagnosis before culture results. Although 90% (N = 2101) with NAAT had positive test results, 9% (N = 217) had falsely negative NAAT results, and 0.8% (N = 18) had indeterminate NAAT results. The median time from specimen collection to TB treatment initiation was shorter when NAAT was used (3 vs 14 days, P < .0001), and patients with a positive NAAT result initiated treatment earlier than patients with a falsely negative result (1 vs 11 days from NAAT report, P < .0001). We confirmed the increased sensitivity of NAAT compared with acid-fast bacilli (AFB) smear microscopy in our study population; 92 of 145 AFB smear-negative patients had positive NAATs. Median time from specimen collection to NAAT result report differed by health jurisdiction, from 1 to 11 working days.

CONCLUSIONS

Increased use of NAATs in diagnosis of pulmonary TB could decrease the time-to-treatment initiation and consequently decrease transmission. However, differential use and access to NAAT may prevent full realization of NAAT benefits in California.

Xpert®MTB/RIF for the Diagnosis of Tuberculosis in a Remote Arctic Setting: Impact on Cost and Time to Treatment Initiation

BACKGROUND

Tuberculosis (TB) remains a significant health problem in the Canadian Arctic. Substantial health system delays in TB diagnosis can occur, in part due to the lack of capacity for onsite microbiologic testing. A study recently evaluated the yield and impact of a rapid automated PCR test (Xpert®MTB/RIF) for the diagnosis of TB in Iqaluit (Nunavut). We conducted an economic analysis to evaluate the expected cost relative to the expected reduction in time to treatment initiation, with the addition of Xpert®MTB/RIF to the current diagnostic and treatment algorithms used in this setting.

METHODS

A decision analysis model compared current microbiologic testing to a scenario where Xpert®MTB/RIF was added to the current diagnostic algorithm for active TB, and incorporated costs and clinical endpoints from the Iqaluit study. Several sensitivity analyses that considered alternative use were also considered. We estimated days to TB diagnosis and treatment initiation, health system costs, and the incremental cost per treatment day gained for each individual evaluated for possible TB.

RESULTS

With the addition of Xpert®MTB/RIF, costs increased while days to TB treatment initiation were reduced. The incremental cost per treatment day gained (per individual investigated for TB) was $164 (95% uncertainty range $85, $452). In a sensitivity analysis that considered hospital discharge after a single negative Xpert®MTB/RIF, the Xpert®MTB/RIF scenario was cost saving.

INTERPRETATION

Adding Xpert®MTB/RIF to the current diagnostic algorithm for TB in Nunavut appears to reduce time to diagnosis and treatment at reasonable cost. It may be especially well suited to overcome some of the other logistical barriers that are unique to this and other remote communities.

Infectious Diseases (ID) Learning Unit: How Rapidly to Evaluate for Active Tuberculosis Disease in Low-Prevalence Settings

With declining tuberculosis (TB) incidence in low-prevalence settings, many clinicians are likely unaware that the approach to diagnosing active TB is evolving with newer technologies. Rapid molecular assays are commercially available, and more are likely to enter the market in the coming years. These tests, such as the Xpert MTB/RIF, which can detect TB and drug-resistance in 2 hours, are increasingly used in settings with higher TB prevalence; however, uptake has been slower in low-prevalence settings. Newer algorithms incorporating rapid TB diagnostics have the ability to alter current clinical and infection control practice patterns. In this learning unit, we review current and newly available tests for the detection of active TB disease and their usage in low-prevalence settings.

Impact of Molecular Diagnostics for Tuberculosis on Patient-Important Outcomes: A Systematic Review of Study Methodologies

BACKGROUND

Several reviews on the accuracy of Tuberculosis (TB) Nucleic Acid Amplification Tests (NAATs) have been performed but the evidence on their impact on patient-important outcomes has not been systematically reviewed. Given the recent increase in research evaluating such outcomes and the growing list of TB NAATs that will reach the market over the coming years, there is a need to bring together the existing evidence on impact, rather than accuracy. We aimed to assess the approaches that have been employed to measure the impact of TB NAATs on patient-important outcomes in adults with possible pulmonary TB and/or drug-resistant TB.

METHODS

We first develop a conceptual framework to clarify through which mechanisms the improved technical performance of a novel TB test may lead to improved patient outcomes and outline which designs may be used to measure them. We then systematically review the literature on studies attempting to assess the impact of molecular TB diagnostics on such outcomes and provide a narrative synthesis of designs used, outcomes assessed and risk of bias across different study designs.

RESULTS

We found 25 eligible studies that assessed a wide range of outcomes and utilized a variety of experimental and observational study designs. Many potentially strong design options have never been used. We found that much of the available evidence on patient-important outcomes comes from a small number of settings with particular epidemiological and operational context and that confounding, time trends and incomplete outcome data receive insufficient attention.

CONCLUSIONS

A broader range of designs should be considered when designing studies to assess the impact of TB diagnostics on patient outcomes and more attention needs to be paid to the analysis as concerns about confounding and selection bias become relevant in addition to those on measurement that are of greatest concern in accuracy studies.

Diagnostic Accuracy of Xpert Test in Tuberculosis Detection: A Systematic Review and Meta-analysis

BACKGROUND

World Health Organization (WHO) recommends the use of Xpert MTB/RIF assay for rapid diagnosis of tuberculosis (TB) and detection of rifampicin resistance. This systematic review was done to know about the diagnostic accuracy and cost-effectiveness of the Xpert MTB/RIF assay.

METHODS

A systematic literature search was conducted in following databases: Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews, MEDLINE, PUBMED, Scopus, Science Direct and Google Scholar for relevant studies for studies published between 2010 and December 2014. Studies given in the systematic reviews were accessed separately and used for analysis. Selection of studies, data extraction and assessment of quality of included studies was performed independently by two reviewers. Studies evaluating the diagnostic accuracy of Xpert MTB/RIF assay among adult or predominantly adult patients (≥14 years), presumed to have pulmonary TB with or without HIV infection were included in the review. Also, studies that had assessed the diagnostic accuracy of Xpert MTB/RIF assay using sputum and other respiratory specimens were included.

RESULTS

The included studies had a low risk of any form of bias, showing that findings are of high scientific validity and credibility. Quantitative analysis of 37 included studies shows that Xpert MTB/RIF is an accurate diagnostic test for TB and detection of rifampicin resistance.

CONCLUSION

Xpert MTB/RIF assay is a robust, sensitive and specific test for accurate diagnosis of tuberculosis as compared to conventional tests like culture and microscopic examination.

Bridging the gap between evidence and policy for infectious diseases: How models can aid public health decision-making

The dominant approach to decision-making in public health policy for infectious diseases relies heavily on expert opinion, which often applies empirical evidence to policy questions in a manner that is neither systematic nor transparent. Although systematic reviews are frequently commissioned to inform specific components of policy (such as efficacy), the same process is rarely applied to the full decision-making process. Mathematical models provide a mechanism through which empirical evidence can be methodically and transparently integrated to address such questions. However, such models are often considered difficult to interpret. In addition, models provide estimates that need to be iteratively reevaluated as new data or considerations arise. Using the case study of a novel diagnostic for tuberculosis, a framework for improved collaboration between public health decision-makers and mathematical modellers that could lead to more transparent and evidence-driven policy decisions for infectious diseases in the future is proposed. The framework proposes that policymakers should establish long-term collaborations with modellers to address key questions, and that modellers should strive to provide clear explanations of the uncertainty of model structure and outputs. Doing so will improve the applicability of models and clarify their limitations when used to inform real-world public health policy decisions.

Shortening Isolation of Patients With Suspected Tuberculosis by Using Polymerase Chain Reaction Analysis: A Nationwide Cross-sectional Study

BACKGROUND

Isolation of patients suspected for pulmonary tuberculosis is guided by serial sputum smears. This can result in isolation for days for patients with noncontagious tuberculosis. To determine whether a single sample negative for Mycobacterium tuberculosis complex at polymerase chain reaction (PCR) can guide isolation.

METHODS

We retrospectively evaluated sputum samples analyzed for M. tuberculosis complex at the International Reference Laboratory of Mycobacteriology, Copenhagen, Denmark in 2002-2011. We selected culture-confirmed tuberculosis cases with ≥3 samples within 14 days before or after the initial culture-positive sample. We repeated the process for those with ≥2 samples within 28 days. The primary outcome was PCR-negative, smear-positive patients.

RESULTS

We included 53 533 sputum samples from 20 928 individuals; 1636 had culture-confirmed tuberculosis. Of these, 856 had ≥3 sputum samples analyzed within the 28 days, and 482 had ≥1 PCR result. Nine patients (2.5% of smear-positive patients) were smear positive/PCR negative; 8 of the 9 had a smear-positive result in only 1 of 3 samples, and 5 had a low smear grade. Of 722 patients with 2 samples, 7 (1.3% of smear-positive patients) were smear positive/PCR negative. Overall, none were smear positive for the sample that produced the negative PCR result.

CONCLUSIONS

Primary PCR identified >97% of serial smear-positive cases. The majority of the missed cases had low-grade smears. Nevertheless, the occurrence of smear-positive/PCR-negative cases underlines the importance of increasing the quantity and quality of samples. Moreover, it is important that samples analyzed with PCR are cultured, owing to higher-sensitivity drug susceptibility testing, differential diagnosis, and surveillance.

Review of nucleic acid amplification tests and clinical prediction rules for diagnosis of tuberculosis in acute care facilities

Tuberculosis (TB) remains an important cause of hospitalization and mortality in the United States. Prevention of TB transmission in acute care facilities relies on prompt identification and implementation of airborne isolation, rapid diagnosis, and treatment of presumptive pulmonary TB patients. In areas with low TB burden, this strategy may result in inefficient utilization of airborne infection isolation rooms (AIIRs). We reviewed TB epidemiology and diagnostic approaches to inform optimal TB detection in low-burden settings. Published clinical prediction rules for individual studies have a sensitivity ranging from 81% to 100% and specificity ranging from 14% to 63% for detection of culture-positive pulmonary TB patients admitted to acute care facilities. Nucleic acid amplification tests (NAATs) have a specificity of >98%, and the sensitivity of NAATs varies by acid-fast bacilli sputum smear status (positive smear, ≥95%; negative smear, 50%-70%). We propose an infection prevention strategy using a clinical prediction rule to identify patients who warrant diagnostic evaluation for TB in an AIIR with an NAAT. Future studies are needed to evaluate whether use of clinical prediction rules and NAATs results in optimized utilization of AIIRs and improved detection and treatment of presumptive pulmonary TB patients.

Revised device labeling for the Cepheid Xpert MTB/RIF assay for detecting Mycobacterium tuberculosis

The Food and Drug Administration (FDA) has cleared the Xpert MTB/RIF Assay (Cepheid; Sunnyvale, California) with an expanded intended use that includes testing of either one or two sputum specimens as an alternative to examination of serial acid-fast stained sputum smears to aid in the decision of whether continued airborne infection isolation (AII) is warranted for patients with suspected pulmonary tuberculosis. This change reflects the outcome of a recent multicenter international study demonstrating that negative Xpert MTB/RIF Assay results from either one or two sputum specimens are highly predictive of the results of two or three negative acid-fast sputum smears.