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Within-Subject Interlaboratory Variability of QuantiFERON-TB Gold In-Tube Tests  [PDF]
William C. Whitworth, Lanette R. Hamilton, Donald J. Goodwin, Carlos Barrera, Kevin B. West, Laura Racster, Laura J. Daniels, Stella O. Chuke, Brandon H. Campbell, Jamaria Bohanon, Atheer T. Jaffar, Wanzer Drane, David Maserang, Gerald H. Mazurek
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043790
Abstract: Background The QuantiFERON?-TB Gold In-Tube test (QFT-GIT) is a viable alternative to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, within-subject variability may limit test utility. To assess variability, we compared results from the same subjects when QFT-GIT enzyme-linked immunosorbent assays (ELISAs) were performed in different laboratories. Methods Subjects were recruited at two sites and blood was tested in three labs. Two labs used the same type of automated ELISA workstation, 8-point calibration curves, and electronic data transfer. The third lab used a different automated ELISA workstation, 4-point calibration curves, and manual data entry. Variability was assessed by interpretation agreement and comparison of interferon-γ (IFN-γ) measurements. Data for subjects with discordant interpretations or discrepancies in TB Response >0.05 IU/mL were verified or corrected, and variability was reassessed using a reconciled dataset. Results Ninety-seven subjects had results from three labs. Eleven (11.3%) had discordant interpretations and 72 (74.2%) had discrepancies >0.05 IU/mL using unreconciled results. After correction of manual data entry errors for 9 subjects, and exclusion of 6 subjects due to methodological errors, 7 (7.7%) subjects were discordant. Of these, 6 (85.7%) had all TB Responses within 0.25 IU/mL of the manufacturer's recommended cutoff. Non-uniform error of measurement was observed, with greater variation in higher IFN-γ measurements. Within-subject standard deviation for TB Response was as high as 0.16 IU/mL, and limits of agreement ranged from ?0.46 to 0.43 IU/mL for subjects with mean TB Response within 0.25 IU/mL of the cutoff. Conclusion Greater interlaboratory variability was associated with manual data entry and higher IFN-γ measurements. Manual data entry should be avoided. Because variability in measuring TB Response may affect interpretation, especially near the cutoff, consideration should be given to developing a range of values near the cutoff to be interpreted as “borderline,” rather than negative or positive.
Unusual Interferon Gamma Measurements with QuantiFERON-TB Gold and QuantiFERON-TB Gold In-Tube Tests
Richard D. Powell III,William C. Whitworth,John Bernardo,Patrick K. Moonan,Gerald H. Mazurek
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020061
Abstract: Interferon gamma (IFN-γ) release assays, such as QuantiFERON?-TB Gold test (QFT-G) and QuantiFERON?-TB Gold In-Tube test (QFT-GIT) are designed to detect M. tuberculosis (Mtb) infection. Recognition of unusual IFN-γ measurements may help indicate inaccurate results.
Negative effect of smoking on the performance of the QuantiFERON TB gold in tube test  [cached]
Aabye Martine G,Hermansen Thomas Stig,Ruhwald Morten,PrayGod George
BMC Infectious Diseases , 2012, DOI: 10.1186/1471-2334-12-379
Abstract: Background False negative and indeterminate Interferon Gamma Release Assay (IGRA) results are a well documented problem. Cigarette smoking is known to increase the risk of tuberculosis (TB) and to impair Interferon-gamma (IFN-γ) responses to antigenic challenge, but the impact of smoking on IGRA performance is not known. The aim of this study was to evaluate the effect of smoking on IGRA performance in TB patients in a low and high TB prevalence setting respectively. Methods Patients with confirmed TB from Denmark (DK, n = 34; 20 smokers) and Tanzania (TZ, n = 172; 23 smokers) were tested with the QuantiFERON-TB Gold In tube (QFT). Median IFN-γ level in smokers and non smokers were compared and smoking was analysed as a risk factor for false negative and indeterminate QFT results. Results Smokers from both DK and TZ had lower IFN-γ antigen responses (median 0.9 vs. 4.2 IU/ml, p = 0.04 and 0.4 vs. 1.6, p < 0.01), less positive (50 vs. 86%, p = 0.03 and 48 vs. 75%, p < 0.01) and more false negative (45 vs. 0%, p < 0.01 and 26 vs. 11%, p = 0.04) QFT results. In Tanzanian patients, logistic regression analysis adjusted for sex, age, HIV and alcohol consumption showed an association of smoking with false negative (OR 17.1, CI: 3.0-99.1, p < 0.01) and indeterminate QFT results (OR 5.1, CI: 1.2-21.3, p = 0.02). Conclusions Cigarette smoking was associated with false negative and indeterminate IGRA results in both a high and a low TB endemic setting independent of HIV status.
Sensitivity of the Quantiferon-Gold In-Tube Assay in Sputum Smear Positive TB Cases in Indonesia  [PDF]
Merrin Rutherford,Bachti Alisjahbana,Winni Maharani,Hedy Sampurno,Reinout van Crevel,Philip C. Hill
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012020
Abstract: As part of a formal evaluation of the Quantiferon-Gold in-tube assay (QFT-IT) for latent TB infection we compared its sensitivity to the tuberculin skin test (TST) in confirmed adult TB cases in Indonesia. Smear-positive TB disease was used as a proxy gold standard for latent TB infection.
Monitoring the efficacy of anti-TB therapy by using the QuantiFERON-TB Gold In tube test
R. Markova,R. Drenska,Y. Todorova,V. Terzieva
European Respiratory Review , 2008,
Abstract: Monitoring the efficacy of anti-TB therapy is crucial for the better control of the spread of MTB infection, but it is often difficult especially for patients without microbiological confirmation of the disease. IGRAs are novel indirect blood tests for M. tuberculosis infection and a promising marker of mycobacterial burden and disease activity. To describe our experience with the use of the QuantiFERON-TB Gold In tube assay for monitoring of anti-TB therapy in patients with active disease 30 patients with active TB, all HIV-negative and BCG-vaccinated at birth, were studied before and after three and eight months of anti-TB therapy. The whole blood QFT G In tube assay was used to measure the MTB-specific IFN-gamma responses. Before therapy 28/30 patients had positive results in QFT G In tube (QFT) and two – indeterminate. Three months after initiation of treatment all subjects tested were found positive. On month eight a significant decrease of MTB-specific responses was found in all patients but only 17/30 (56.7%) turned negative in QFT. Three of 13 patients with a positive response at the end of month eight, continued to have microbiological isolation and absence of clinical improvement (fig. 1, table 1). On the basis of the results obtained, we concluded that the QFT Gold In tube assay could be used in routine clinical practice for monitoring anti-tuberculosis therapy. Further studies including larger number of patients and longer periods of observation are needed.
A Toolbox for Tuberculosis (TB) Diagnosis: An Indian Multicentric Study (2006–2008). Evaluation of QuantiFERON-TB Gold in Tube for TB Diagnosis  [PDF]
Philippe H. Lagrange, Satheesh K. Thangaraj, Rajeshwar Dayal, Alaka Deshpande, Nirmal K. Ganguly, Enrico Girardi, Beenu Joshi, Kiran Katoch, Vishwa M. Katoch, Manoj Kumar, Vemu Lakshmi, Marc Leportier, Christophe Longuet, Subbalaxmi V. S. Malladi, Deepali Mukerjee, Deepthi Nair, Alamelu Raja, Balambal Raman, Camilla Rodrigues, Pratibha Sharma, Amit Singh, Sarman Singh, Archana Sodha, Basirudeen Syed Ahamed Kabeer, Guy Vernet, Delia Goletti
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073579
Abstract: Background The aim of this multicentric prospective study in India was to assess the performance of the QuantiFERON TB-Gold in tube (QFT-GIT), Tuberculin Skin Test (TST) and microbiological results as additional tools for diagnosing active tuberculosis (TB) and latent infection (LTBI) according to Human Immunodeficiency Virus (HIV) status. Methods Individuals with and without active TB and HIV infection were enrolled between 2006–2008. QFT-GIT and TST results were analyzed per se and in combination with microbiological data. Results Among the 276 individuals (96 active pulmonary TB and 180 no active TB) tested by QFT-GIT, 18 indeterminate results (6.5%) were found, more significantly numerous in the HIV-infected (15/92; 16.3%) than the HIV-uninfected (3/184; 1.6%)(p<0.0001). QFT-GIT sensitivity for active TB was 82.3% and 92.9% respectively after including or excluding indeterminate results. Clinical sensitivity was significantly lower in the HIV-infected (68.4%) than the HIV-uninfected (91.4%) patients (p = 0.0059). LTBI was detected in 49.3% of subjects without active TB but varied according to TB exposure. When the TST and QFT-GIT were concomitantly performed, the respective sensitivity for active TB diagnosis was 95.0% and 85.0% in the HIV-uninfected (p = 0.60), and 66.7% and 51.5% in the HIV-infected patients (p = 0.32). QFT-GIT and TST respective specificity for active TB in the HIV-uninfected was 25.0% and 57.1% (p = 0.028), and 64.8% and 83.3% in the HIV-infected (p = 0.047). In those with active TB, QFT-GIT results were not associated with microbiological parameters (smear grade, liquid culture status, time-to-positivity of culture) or clinical suspicion of active TB score (provided by the clinicians at enrollment). Combining microbiological tests with both immunological tests significantly increased sensitivity for active TB diagnosis (p = 0.0002), especially in the HIV-infected individuals (p = 0.0016). Conclusion QFT-GIT and TST have similar diagnostic value for active TB diagnosis. In HIV-infected patients, combining microbiological tests with both immunological tests significantly increases the sensitivity for active TB diagnosis.
QuantiFERON?-TB Gold In-Tube Performance for Diagnosing Active Tuberculosis in Children and Adults in a High Burden Setting  [PDF]
Michala V. Rose, Godfather Kimaro, Thomas N. Nissen, Inge Kroidl, Michael Hoelscher, Ib C. Bygbjerg, Sayoki G. Mfinanga, Pernille Ravn
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037851
Abstract: Aim To determine whether QuantiFERON?-TB Gold In-Tube (QFT) can contribute to the diagnosis of active tuberculosis (TB) in children in a high-burden setting and to assess the performance of QFT and tuberculin skin test (TST) in a prospective cohort of TB suspect children compared to adults with confirmed TB in Tanzania. Methods Sensitivity and specificity of QFT and TST for diagnosing active TB as well as indeterminate QFT rates and IFN-γ levels were assessed in 211 TB suspect children in a Tanzanian district hospital and contrasted in 90 adults with confirmed pulmonary TB. Results Sensitivity of QFT and TST in children with confirmed TB was 19% (5/27) and 6% (2/31) respectively. In adults sensitivity of QFT and TST was 84% (73/87) and 85% (63/74). The QFT indeterminate rate in children and adults was 27% and 3%. Median levels of IFN-γ were lower in children than adults, particularly children <2 years and HIV infected. An indeterminate result was associated with age <2 years but not malnutrition or HIV status. Overall childhood mortality was 19% and associated with an indeterminate QFT result at baseline. Conclusion QFT and TST showed poor performance and a surprisingly low sensitivity in children. In contrast the performance in Tanzanian adults was good and comparable to performance in high-income countries. Indeterminate results in children were associated with young age and increased mortality. Neither test can be recommended for diagnosing active TB in children with immature or impaired immunity in a high-burden setting.
Observational Study of QuantiFERON?-TB Gold In-Tube Assay in Tuberculosis Contacts in a Low Incidence Area  [PDF]
Emmanuel Bergot, Eglantine Haustraete, Brigitte Malbruny, Romain Magnier, Marie-Anne Salaün, Gérard Zalcman
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043520
Abstract: Background QuantiFERON?-TB Gold in-Tube (QFT) assay is a recently developed test to assess latent tuberculosis infection in contagious tuberculosis (TB) contact subjects. To assess the QFT assay in recently exposed contacts of active tuberculosis patients in a French area with low TB incidence but high Bacille Calmette-Guerin coverage, and evaluate progression rates to TB disease. Methodology/Principal Findings Between January 2007 and December 2009, 687 contacts of culture-confirmed tuberculosis cases underwent the QFT assay, with tuberculin skin test (TST) in 473, and a 34 months mean follow-up. Of 687 contacts, 148 were QFT positive, while 526 were negative and 13 indeterminate. QFT was positive in 35% of individuals with TST ≥10 mm, 47.5% with TST ≥15 mm or phlyctenular, but in 21% of cases in which two-step TST (M0 and M3) remained negative. Conversely, QFT was negative in 69% of cases with two-step TST showing conversion from negative to positive. All indeterminate QFT were associated with TST induration <10 mm in diameter. For 29 QFT-positive subjects, no chemoprophylaxis was given due to medical contraindications. Of the remaining 119 QFT-positive contacts, 97accepted chemoprophylaxis (81.5%), and 79 (81.4%) completed the treatment. Two contacts progressed to TB disease: one subject was QFT positive and had declined chemoprophylaxis, while the other one was QFT negative. QFT positive predictive value for progression to TB was 1.96% (1/51) with a 99.8% (525/526) negative predictive value. Conclusions/Significance Our results confirm the safety of the QFT-based strategy for assessing the TB chemoprophylaxis indication, as only one contact developed TB disease out of 526 QFT-negative subjects.
Tuberculosis Screening by Tuberculosis Skin Test or QuantiFERON?-TB Gold In-Tube Assay among an Immigrant Population with a High Prevalence of Tuberculosis and BCG Vaccination  [PDF]
John A. Painter, Edward A. Graviss, Hoang Hoa Hai, Duong Thi Cam Nhung, Tran Thi Thanh Nga, Ngan P. Ha, Kirsten Wall, Le Thien Huong Loan, Matt Parker, Lilia Manangan, Rick O’Brien, Susan A. Maloney, R. M. Hoekstra, Randall Reves
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0082727
Abstract: Rationale Each year 1 million persons acquire permanent U.S. residency visas after tuberculosis (TB) screening. Most applicants undergo a 2-stage screening with tuberculin skin test (TST) followed by CXR only if TST-positive at > 5 mm. Due to cross reaction with bacillus Calmette-Guérin (BCG), TST may yield false positive results in BCG-vaccinated persons. Interferon gamma release assays exclude antigens found in BCG. In Vietnam, like most high TB-prevalence countries, there is universal BCG vaccination at birth. Objectives 1. Compare the sensitivity of QuantiFERON ?-TB Gold In-Tube Assay (QFT) and TST for culture-positive pulmonary TB. 2. Compare the age-specific and overall prevalence of positive TST and QFT among applicants with normal and abnormal CXR. Methods We obtained TST and QFT results on 996 applicants with abnormal CXR, of whom 132 had TB, and 479 with normal CXR. Results The sensitivity for tuberculosis was 86.4% for QFT; 89.4%, 81.1%, and 52.3% for TST at 5, 10, and 15 mm. The estimated prevalence of positive results at age 15–19 years was 22% and 42% for QFT and TST at 10 mm, respectively. The prevalence increased thereafter by 0.7% year of age for TST and 2.1% for QFT, the latter being more consistent with the increase in TB among applicants. Conclusions During 2-stage screening, QFT is as sensitive as TST in detecting TB with fewer requiring CXR and being diagnosed with LTBI. These data support the use of QFT over TST in this population.?
The Performance of Quantiferon TB Gold In-Tube as a Screening Tool in Paediatric Rheumatology prior to Initiation of Infliximab: A Single Centre's Experience  [PDF]
Despoina Maritsi,Muthana Al-Obadi,Paul A. Brogan,Despina Eleftheriou,Garth L. J. Dixon
ISRN Rheumatology , 2011, DOI: 10.5402/2011/505171
Abstract: Background. Patients with autoimmune diseases and latent tuberculosis infection (LTBI) are at risk of developing catastrophic tuberculosis disease following infliximab treatment. Quantiferon-TB gold in-Tube (QTB) has proven a more accurate screening tool than tuberculin skin test (TST) in adult populations. Objectives. To assess the utility and validity of QTB in children, prior to treatment with infliximab. Methods. Retrospective cohort of patients started on infliximab following endorsement of QTB as a screening tool by the NICE guidelines in 2006. Results. Twenty three patients (12 females and 11 males) were included in the study. A chest radiograph (CXR) and QTB was performed prior to starting infliximab. Fourteen patients had a recorded negative TST result. One patient had a positive QTB while two had indeterminate results. Their CXRs were not suggestive of TB and TSTs were negative. The patients with indeterminate results were started on infliximab and had regular clinical assessment for TB disease. Repeat QTB was negative in one while remained indeterminate in the other. None of our 23 patients developed TB. Conclusion. QTB is a useful screen tool for LTBI. Indeterminate results warrant careful assessment and re-evaluation, but should not preclude from initiation of anti TNF treatment. 1. Background Antitumor Necrosis Factor alpha (TNFα) agents are a rapidly developing field of medicines in pediatric rheumatology. Recent papers have presented the efficacy and effectiveness of anti-TNFα therapy in disease control and improvement in quality of life. Agents commonly used include infliximab, an anti-TNFα chimeric monoclonal antibody, etanercept, an anti-TNFα receptor fusion IgG protein, and adalimumab, a humanized monoclonal antibody acting as TNFα receptor blocker. However, initiation of anti-TNFα treatment is not without risk. TNF is released by macrophages and is a potent regulator for granuloma formation and limitation of the mycobacterium tuberculosis (TB) infection. Anti-TNFα medications suppress TNF actions and inhibit its restrictive role in controlling TB, thus potentially leading to reactivation of TB disease in those with LTBI. This may have catastrophic consequences especially in patients with an already dysregulated and compromised immune system [1]. A tool that could rule out TB infection prior to anti-TNFα medications is therefore highly desirable. Over the last three years the use of Interferon gamma releasing assays (IGRAs) has been increasingly introduced in order to verify or rule out latent TB infection (LTBI) [2]. There are
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