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  • American Society for Microbiology  (8)
  • 1
    Online Resource
    Online Resource
    Preanalytical Delay Reduces Sensitivity of QuantiFERON-TB Gold In-Tube Assay for Detection of Latent Tuberculosis Infection
    American Society for Microbiology ; 2011
    In:  Journal of Clinical Microbiology Vol. 49, No. 8 ( 2011-08), p. 3061-3064
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 49, No. 8 ( 2011-08), p. 3061-3064
    Abstract: The effects of incubation delays on the accuracy of the QuantiFERON-TB gold in-tube assay (QFT-GIT) were measured. Compared to immediate incubation, 6- and 12-hour delays resulted in positive-to-negative reversion rates of 19% (5/26) and 22% (5/23), respectively. These findings underscore the need for standardizing QFT-GIT preanalytical practices.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.01136-11
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2011
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Clostridium difficile PCR Cycle Threshold Predicts Free Toxin
    American Society for Microbiology ; 2017
    In:  Journal of Clinical Microbiology Vol. 55, No. 9 ( 2017-09), p. 2651-2660
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 55, No. 9 ( 2017-09), p. 2651-2660
    Abstract: There is no stand-alone Clostridium difficile diagnostic that can sensitively and rapidly detect fecal free toxins. We investigated the performance of the C. difficile PCR cycle threshold ( C T ) for predicting free toxin status. Consecutive stool samples ( n = 312) positive for toxigenic C. difficile by the GeneXpert C. difficile /Epi tcdB PCR assay were tested with the rapid membrane C. Diff Quik Chek Complete immunoassay (RMEIA). RMEIA toxin-negative samples were tested with the cell cytotoxicity neutralization assay (CCNA) and tgcBIOMICS enzyme-linked immunosorbent assay (ELISA). Using RMEIA alone or in combination with CCNA and/or ELISA as the reference method, the accuracy of C T was measured at different C T cutoffs. Using RMEIA as the reference method, a C T cutoff of 26.35 detected toxin-positive samples with a sensitivity, specificity, positive predictive value, and negative predictive value of 96.0% (95% confidence interval [CI], 90.2% to 98.9%), 65.9% (95% CI, 59.0% to 72.2%), 57.4% (95% CI, 52.7% to 62%), and 97.1% (95% CI, 92.8% to 98.9), respectively. Inclusion of CCNA in the reference method improved C T specificity to 78.0% (95% CI, 70.7% to 84.2%). Intercartridge lot C T variability measured as the average coefficient of variation was 2.8% (95% CI, 1.2% to 3.2%). Standardizing the input stool volume did not improve C T toxin specificity. The median C T values were not significantly different between stool samples with Bristol scores of 5, 6, and 7, between pediatric and adult samples, or between presumptive 027 and non-027 strains. In addition to sensitively detecting toxigenic C. difficile in stool, on-demand PCR may also be used to accurately predict toxin-negative stool samples, thus providing additional results in PCR-positive stool samples to guide therapy.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.00563-17
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2017
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Evaluation of QuantiFERON-TB Gold-Plus in Health Care Workers in a Low-Incidence Setting
    American Society for Microbiology ; 2017
    In:  Journal of Clinical Microbiology Vol. 55, No. 6 ( 2017-06), p. 1650-1657
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 55, No. 6 ( 2017-06), p. 1650-1657
    Abstract: Although launched in 2015, little is known about the accuracy of QuantiFERON-TB Gold-Plus (QFT-Plus) for diagnosis of latent M. tuberculosis infection (LTBI). Unlike its predecessor, QFT-Plus utilizes two antigen tubes to elicit an immune response from CD4 + and CD8 + T lymphocytes. We conducted a cross-sectional study in low-risk health care workers (HCWs) at a single U.S. center to compare QFT-Plus to QuantiFERON-TB Gold in-tube (QFT). A total of 989 HCWs were tested with both QFT and QFT-Plus. Risk factors for LTBI were obtained from a questionnaire. QFT-Plus was considered positive if either antigen tube 1 (TB1) or TB2 tested positive, per the manufacturer's recommendations, or if both TB1 and TB2 tested positive, using a conservative definition. Results were compared using Cohen's kappa and linear regression, respectively. Agreement of QFT with QFT-Plus was high, at 95.6% (95% confidence interval [CI], 94.3 to 96.9; kappa, 0.57). The majority of discordant results between QFT and QFT-Plus TB1 (84.8%) and QFT and QFT-Plus TB2 (88.6%) fell within the range of 0.2 to 0.7 IU/ml. The positivity rate in 626 HCWs with no identifiable risk factors and no self-reported history of positive LTBI tests was 2.1% (CI, 1.0 to 3.2) and 3.0% (CI, 1.7 to 4.3) with QFT and QFT-Plus, respectively. A conservative definition of a QFT-Plus-positive result yielded a positivity rate of 1.0% (CI, 0.2 to 1.7; P value of 0.0002 versus QFT-Plus and 0.07 versus QFT). On follow-up testing, of 11 HCWs with discordant QFT-Plus results, 90.9% (10/11) had a negative QFT result. The QFT-Plus assay showed a high degree of agreement with QFT in U.S. HCWs. A conservative interpretation of QFT-Plus eliminated nearly all nonreproducible positive results in low-risk HCWs. Larger studies are needed to validate the latter finding and to more clearly define conditions under which a conservative interpretation can be used to minimize nonreproducible positive results in low-risk populations.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.02498-16
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2017
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Impact of Blood Volume, Tube Shaking, and Incubation Time on Reproducibility of QuantiFERON-TB Gold In-Tube Assay
    American Society for Microbiology ; 2013
    In:  Journal of Clinical Microbiology Vol. 51, No. 11 ( 2013-11), p. 3521-3526
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 51, No. 11 ( 2013-11), p. 3521-3526
    Abstract: Gamma interferon (IFN-γ) release assays (IGRAs) are functional assays used serially to measure the efficacy of novel tuberculosis (TB) vaccines and to screen health care workers for latent tuberculosis infection (LTBI). However, studies have shown nonreproducible IGRA results. In this study, we investigated the effects of blood volume (0.8, 1.0, and 1.2 ml), tube shaking (gentle versus vigorous), and incubation duration (16, 20, and 24 h) on the reproducibility of QuantiFERON-TB Gold In-Tube (QFT-GIT) results for 50 subjects (33 uninfected and 17 infected). The median IFN-γ TB response (TB antigen [Ag] minus nil value) was significantly higher with 0.8 ml blood (1.04 IU/ml) than with 1.0 ml (0.85 IU/ml; P = 0.002) or 1.2 ml (0.49 IU/ml; P 〈 0.001) for subjects with LTBI. Compared with 0.8 ml (11.8%), there were larger proportions of false-negative results with 1.0 ml (29.4%; P = 0.2) and 1.2 ml (41.2%; P = 0.05) of blood for infected subjects. Blood volume did not significantly change the proportions of positive results in uninfected controls. Compared with gentle shaking, vigorous shaking increased the median IFN-γ response in nil (0.04 versus 0.06 IU/ml; P 〈 0.001) and TB Ag (0.12 versus 0.24 IU/ml; P = 0.004) tubes and increased TB responses (TB Ag vigorous minus nil gentle ) (0.02 versus 0.08 IU/ml; P = 0.004). The duration of incubation did not have a significant impact on the proportion of positive results in uninfected or infected subjects. This study identified blood volume and tube shaking as novel preanalytical sources of variability which require further standardization in order to improve the quality and reproducibility of QFT-GIT results.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.01627-13
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2013
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Can a Simple Flotation Method Lower the Limit of Detection of Mycobacterium tuberculosis in Extrapulmonary Samples Analyzed by the GeneXpert MTB/RIF Assay?
    American Society for Microbiology ; 2012
    In:  Journal of Clinical Microbiology Vol. 50, No. 7 ( 2012-07), p. 2272-2276
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 50, No. 7 ( 2012-07), p. 2272-2276
    Abstract: The rapid and accurate diagnosis of tuberculosis (TB) in children and extrapulmonary TB in adults continues to be a challenge. In this study, we determined the lower limit of detection (LOD) of the GeneXpert MTB/RIF assay with nonrespiratory specimens and investigated the utility of flotation procedures for concentrating the bacilli. Clinical specimens (9 cerebrospinal fluid [CSF], 13 gastric aspirate, 8 tissue, and 17 stool) were spiked with single-celled Mycobacterium tuberculosis , and the LOD of the GeneXpert assay was determined. Flotation studies were conducted with sucrose and NaCl, and the cycle thresholds of the MTB/RIF assay were compared between treated and untreated samples. There was no significant difference between the LODs of the GeneXpert assay with saline solution (median, 33 CFU/ml) and CSF (median, 25 CFU/ml) ( P 〉 0.05) or gastric aspirate samples (median, 58 CFU/ml) ( P 〉 0.05). The LOD with spiked tissue (median, 1,525 CFU/ml) and stool samples (median, 6,800 CFU/ml) was significantly elevated compared to that determined with saline solution ( P ≤ 0.05 and ≤ 0.0005, respectively). Flotation studies with sucrose or NaCl did not consistently result in lowered cycle thresholds in stool or gastric aspirates, but a cycle reduction of 〉 10 was achieved in two of the three pooled CSF samples. Unlike the results seen with tissue and stool samples, there was no significant PCR inhibition in the MTB/RIF assay with CSF and gastric aspirates. Although preconcentration of CSF samples with sucrose and NaCl may enhance detection of M. tuberculosis by PCR, further advances are needed to concentrate the bacilli and eliminate PCR inhibitors in paucibacillary nonrespiratory samples.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.01012-12
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2012
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Interferon Gamma Release Assays for Latent Tuberculosis: What Are the Sources of Variability?
    American Society for Microbiology ; 2016
    In:  Journal of Clinical Microbiology Vol. 54, No. 4 ( 2016-04), p. 845-850
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 54, No. 4 ( 2016-04), p. 845-850
    Abstract: Interferon gamma release assays (IGRAs) are blood-based tests intended for diagnosis of latent tuberculosis infection (LTBI). IGRAs offer logistical advantages and are supposed to offer improved specificity over the tuberculin skin test (TST). However, recent serial testing studies of low-risk individuals have revealed higher false conversion rates with IGRAs than with TST. Reproducibility studies have identified various sources of variability that contribute to nonreproducible results. Sources of variability can be broadly classified as preanalytical, analytical, postanalytical, manufacturing, and immunological. In this minireview, we summarize known sources of variability and their impact on IGRA results. We also provide recommendations on how to minimize sources of IGRA variability.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.02803-15
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2016
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Xpert MTB/XDR: a 10-Color Reflex Assay Suitable for Point-of-Care Settings To Detect Isoniazid, Fluoroquinolone, and Second-Line-Injectable-Drug Resistance Directly from Mycobacterium tuberculosis-Positive Sputum
    American Society for Microbiology ; 2021
    In:  Journal of Clinical Microbiology Vol. 59, No. 3 ( 2021-02-18)
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 59, No. 3 ( 2021-02-18)
    Abstract: We describe the design, development, analytical performance, and a limited clinical evaluation of the 10-color Xpert MTB/XDR assay (CE-IVD only, not for sale in the United States). This assay is intended as a reflex test to detect resistance to isoniazid (INH), fluoroquinolones (FLQ), ethionamide (ETH), and second-line injectable drugs (SLIDs) in unprocessed sputum samples and concentrated sputum sediments which are positive for Mycobacterium tuberculosis . The Xpert MTB/XDR assay simultaneously amplifies eight genes and promoter regions in M. tuberculosis and analyzes melting temperatures ( T m s) using sloppy molecular beacon (SMB) probes to identify mutations associated with INH, FLQ, ETH, and SLID resistance. Results can be obtained in under 90 min using 10-color GeneXpert modules. The assay can differentiate low- versus high-level resistance to INH and FLQ as well as cross-resistance versus individual resistance to SLIDs by identifying mutation-specific T m s or T m patterns generated by the SMB probes. The assay has a limit of detection comparable to that of the Xpert MTB/RIF assay and successfully detected 16 clinically significant mutations in a challenge set of clinical isolate DNA. In a clinical study performed at two sites with 100 sputum and 214 clinical isolates, the assay showed a sensitivity of 94% to 100% and a specificity of 100% for all drugs except for ETH compared to that of sequencing. The sensitivity and specificity were in the same ranges as those of phenotypic drug-susceptibility testing. Used in combination with a primary tuberculosis diagnostic test, this assay should expand the capacity for detection of drug-resistant tuberculosis near the point of care.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.02314-20
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2021
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Multicenter Evaluation of the Cepheid Xpert Xpress SARS-CoV-2 Test
    American Society for Microbiology ; 2020
    In:  Journal of Clinical Microbiology Vol. 58, No. 8 ( 2020-07-23)
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 58, No. 8 ( 2020-07-23)
    Abstract: Nucleic acid amplification tests (NAATs) are the primary means of identifying acute infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Accurate and fast test results may permit more efficient use of protective and isolation resources and allow rapid therapeutic interventions. We evaluated the analytical and clinical performance characteristics of the Xpert Xpress SARS-CoV-2 (Xpert) test, a rapid, automated molecular test for SARS-CoV-2. Analytical sensitivity and specificity/interference were assessed with infectious SARS-CoV-2; other infectious coronavirus species, including SARS-CoV; and 85 nasopharyngeal swab specimens positive for other respiratory viruses, including endemic human coronaviruses (hCoVs). Clinical performance was assessed using 483 remnant upper- and lower-respiratory-tract specimens previously analyzed by standard-of-care (SOC) NAATs. The limit of detection of the Xpert test was 0.01 PFU/ml. Other hCoVs, including Middle East respiratory syndrome coronavirus, were not detected by the Xpert test. SARS-CoV, a closely related species in the subgenus Sarbecovirus , was detected by a broad-range target (E) but was distinguished from SARS-CoV-2 (SARS-CoV-2-specific N2 target). Compared to SOC NAATs, the positive agreement of the Xpert test was 219/220 (99.5%), and the negative agreement was 250/261 (95.8%). A third tie-breaker NAAT resolved all but three of the discordant results in favor the Xpert test. The Xpert test provided sensitive and accurate detection of SARS-CoV-2 in a variety of upper- and lower-respiratory-tract specimens. The high sensitivity and short time to results of approximately 45 min may impact patient management.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.00926-20
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2020
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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