QuantiFERON-TB Gold In-Tube Test Research Articles

Comparison of tuberculin skin testing and QuantiFERON-TB Gold-In Tube test in health care workers

The purpose of this prospective, cross-sectional observational study was to compare the tuberculin skin testing (TST) with QuantiFERON-TB Gold-In Tube (QTF-GIT) for the detection of latent tuberculosis infection in healthcare workers (HCWs). The study included 78 volunteers who are HCWs at the same tertiary care teaching hospital for chest diseases and tuberculosis. Participants with active tuberculosis, immunodefficiency or malnutrition were not included. The TST was administered by the Mantoux method. Peptides representing ESAT-6, CFP-10 and TB7-7 were used as TB-specific antigens in the whole-blood Interferon-gamma (IFN-g) assay (QTF-GIT). There was a statistically significant relation between the number of Bacillus Calmette-Guerin (BCG) scars and the diameter of TST (p< 0.01). QTF results according to previous BCG vaccinations did not significantly differ (p> 0.05). There was an intermediate concordance between two tests (k: 0.346). QTF-GIT has a sensitivity of 56.14% (both TST and QTF-GIT are positive), specificity of 90.48% (both TST and QTF-GIT are negative); positive predictive value of 94.12% and negative predictive value of 43.18% and accuracy is 65.38%. There was a statistically significant relation between TST diameter and QTF result (p< 0.01). Latent tuberculosis infection prevalance of our study population was 43% according to QTF-GIT test, 73% according to TST and BCG vaccination rate was 87%. In conclusion, TST is affected by previous BCG vaccinations, QTF-GIT is not. We can recommend QTF-GIT test for the detection of latent tuberculosis infection as an alternative to TST in populations with routine BCG vaccination programme.

Adapted T Cell Interferon-Gamma Release Assay for the Diagnosis of Pleural Tuberculosis

Background: Better and more rapid tests are needed for the diagnosis of tuberculous pleural effusion (TPE), given the known limitations of conventional diagnostic tests. Objectives: To estimate diagnostic accuracy of the QuantiFERON-TB Gold In-Tube (QFT-GIT) test (and its components) using data-derived cutoffs in pleural fluid. Methods: The QFT-GIT test was performed on whole blood and pleural fluid from 43 patients with TPE and 29 control subjects (non-TPE). To achieve the objective, QFT-GIT test, estimating likelihood ratios and receiver operating curve analysis were performed. Results: The sensitivity and specificity using the QFT-GIT for the diagnosis of TPE were 48.8% and 79.3%, respectively, in pleural fluid. The best cutoff points for tuberculosis (TB) antigen, nil and TB antigen minus nil results were estimated at 0.70, 0.90 and 0.30 IU/ml, respectively. Area under the curve of TB antigen IFN-γ response was 0.86 (CI: 0.76–0.93), nil tube was 0.80 (CI: 0.69–0.89) and TB antigen minus nil tube was 0.82 (CI: 0.72–0.90). When the best cutoff scores of the nil tubes were set at this value, the results of a likelihood ratio of a positive and a negative test were 9.44 (7.4–12.0) and 0.37 (0.09–1.5), respectively. The percentages of indeterminate results in pleural fluid among the TPE cases were 42% (most of them caused by high nil IFN-γ values) using the QFT-GIT test. Conclusion: QFT-GIT test or its components have poor accuracy in the diagnosis of TPE, largely because of a high number of indeterminate results due to high background IFN-γ production in the TPE.

Prevalence and risk factors of latent tuberculosis infection among health care workers in Malaysia

BackgroundHealth care workers are exposed to patients with tuberculosis and are at risk of nosocomial infection. The aim of this study was to determine the prevalence and factors associated with latent tuberculosis infection among health care workers in Malaysia and also to evaluate the agreement between Quantiferon TB Gold in tube test with Tuberculin Skin Test.MethodsA cross sectional study was conducted at four randomly selected hospitals in the Klang Valley from December 2008 to May 2009. Self administered questionnaire was used to obtain information on health care workers and possible risk factors. The response rate for this study was 90.8% with 954 respondents completed the questionnaire and were tested with Quantiferon TB Gold in tube for latent tuberculosis infection. Agreement between Quantiferon TB Gold in tube and Tuberculin Skin Test was assessed among 95 health care workers who consented to undergo both tests.ResultsThe overall prevalence of latent tuberculosis infection among health care workers was 10.6% (CI: 8.6%; 12.6%). Factors significantly associated with latent tuberculosis infection were aged 35 years and older [9.49 (CI: 2.22; 40.50)], history of living in the same house with close family members or friends who had active tuberculosis [8.69 (CI: 3.00; 25.18)], worked as a nurse [4.65 (CI: 1.10; 19.65)] and being male [3.70 (CI: 1.36; 10.02)]. Agreement between Quantiferon TB Gold in tube test and tuberculin skin test at cut-off points of 10 mm and 15 mm was 50.5% and 82.1% respectively. However, Kappa-agreement was poor for both cut-off points.ConclusionThe prevalence of latent tuberculosis infection in Malaysia was relatively low for an intermediate TB burden country. We could not comment on the occupational risk of latent tuberculosis infection among health care worker compared to the general population as there were no prevalence data available for latent tuberculosis infection in the general population. Kappa agreement between Quantiferon TB gold in-tube and tuberculin skin test was poor.

Comparing the performance of QuantiFERON-TB Gold and Mantoux test in detecting latent tuberculosis infection among Iranian health care workers

The risk of transmission of Mycobacterium tuberculosis from patients with tuberculosis to health care workers (HCWs) has been well documented but little is known about the prevalence of latent tuberculosis infection (LTBI) in Iranian HCWs. The aim of this study was to determine the prevalence of LTBI among HCWs by using IFNgamma-release assay and compare the results with those of tuberculin skin test (TST). Two hundred HCWs were evaluated with both TST and QuantiFERON-TB Gold In Tube test (QFT-GIT). The obtained data were analyzed by SPSS v.16 Software. The participants were 73 males and 127 females with the mean age of 34.36±8.26 years. TST was positive in 105 cases (52.5%) and the QFT results were positive in 17 cases (8.5%). There was poor agreement between the two tests (53%, κ = 0.115). Induration diameter of TST ≥ 10 mm and working duration ≥ 10 years were independent predictors for positive QFT (p = 0.004). Due to the fact that BCG vaccination has been administered routinely to all HCWs in Iran, specific tests should be introduced for high risk groups. QFT thus seems to be more effective for LTBI diagnosis than TST among HCWs with BCG immunization history.

Usefulness of Interferon-Gamma Release Assay for Diagnosis of Tuberculous Fistulae in Ano

Purpose: Interferon gamma release assays (QuantiFERON-TB Gold in Tube test [QFT-GIT]); Cellestis Limited, Victoria, Australia) have been studied for diagnosing pulmonary tuberculosis (TB) or latent TB but there have been no reports on the usefulness of this assay in diagnosing tuberculous anal fistula in actual clinical practices. In this study, we evaluated its diagnostic usefulness in patients with suspected tuberculous anal fistula. Methods: We conducted a retrospective analysis of 119 patients with suspected tuberculous anorectal fistula from May 2007 to May 2009. Diagnosis of tuberculous fistula was concluded by identification of acid-fast bacilli, typical caseating granuloma and successful clinical response to anti-TB chemotherapy. All patients underwent the QFT-GIT and all patients diagnosed with tuberculous anal fistula were analyzed. Results: Of the 119 patients with suspected TB fistula, 51 (43%) patients were classified as having TB fistula, including 31 with confirmed tuberculosis and 20 with probable tuberculosis, and other 68 (57%) were classified as not having tuberculosis. Among the 51 patients with TB fistula, Chronic caseating granuloma, acid-fast bacilli stain, and successful clinical response to anti-TB treatment were positive in 27 (52.9%), 4 (7.8%), and 20 (39.2%), respectively. Of the 51 with TB fistula, 44 had positive QFT-GIT results and 7 had negative results. The sensitivity and specificity of the assay were 86% and 85%, and positive predictive value (PPV) and negative predictive value (NPV) were 81% and 89%, respectively. Conclusion: QFT-GIT is a simple, sensitive, and specific method for the diagnosis of clinically highly suspected TB fistula.

Role of the Quantiferon-TB Test in Ruling Out Pleural Tuberculosis: A Multi-Centre Study

Diagnosing pleural tuberculosis (plTB) might be difficult due to limited sensitivity of conventional microbiology tools. As M. tuberculosis (MTB)-specific T cells are recruited into pleural space in plTB, their detection may provide useful clinical information. To this aim, in addition to standard diagnostic tests, we used the QuantiFERON-TB Gold In-Tube (QFT-IT) test in blood and pleural effusion (PE) samples from 48 patients with clinical suspicion of plTB, 18 (37.5%) of whom had confirmed plTB. Four of them (22.2%) tested positive with a nucleic acid amplification test for MTB. The tuberculin skin test was positive in most confirmed plTB cases (88.9%). Positive QFT-IT tests were significantly more frequent in patients with confirmed plTB, as compared to patients with an alternative diagnosis, both in blood (77.7 vs 36.6%, p=0.006) and in PE samples (83.3% vs 46.6%, p=0.02). In addition, both blood and PE MTB-stimulated IFN-gamma levels were significantly higher in plTB patients (p=0.03 and p=0.0049 vs non-plTB, respectively). In blood samples, QFT-IT had 77.8% sensitivity and 63.3% specificity, resulting in 56.0% positive (PPV) and 82.6% negative (NPV) predictive values. On PE, QFT-IT sensitivity was 83.3% and specificity 53.3% (PPV 51.7% and NPV 84.2%). The optimal AUC-derived cut-off for MTB-stimulated pleural IFN-gamma level was 3.01 IU/mL (77.8% sensitivity, 80% specificity, PPV 68.4% and NPV 82.8%). These data suggest that QFT-IT might have a role in ruling out plTB in clinical practice.

Detection of latent tuberculosis by the tuberculin skin test and a whole-blood interferon-γ release assay, and the development of active tuberculosis in HIV-seropositive persons

This study evaluated the QuantiFERON-TB Gold In-Tube (QFT-GIT; Cellestis, Carnegie, Australia) test and the tuberculin skin test (TST) for the detection of latent tuberculosis infection (LTBI) in HIV-infected adults. One hundred thirty-five HIV-seropositive persons and 135 controls underwent TST and QFT-GIT. HIV-infected patients who gave a positive result on either test were offered chemoprophylaxis. The prevalence of LTBI was 6.7% by TST and 9.6% by QFT-GIT ( P = 0.3) in HIV-seropositive subjects, and 34.8% by TST and 21.5% by QFT-GIT ( P = 0.02) among controls. TST reactivity declined sharply as CD4 + cells fell (15.8%, 10.3%, and 0% for >500, 301–500 and ≤300 CD4 + cells/mm 3, respectively; P = 0.002). A less pronounced fall occurred with QFT-GIT (15.8%, 13.8%, and 0% for >500, 301–500, and <100 CD4 + cells/mm 3, respectively; P = 0.03). No cases of tuberculosis occurred during follow-up (0.26 per 100 person-years). Simultaneous testing with TST and QFT-GIT for targeting of chemoprophylaxis, early in the course of HIV infection, might minimize the risk of tuberculosis in these patients.

Potential of interferon- -inducible protein 10 in improving tuberculosis diagnosis in HIV-infected patients

To the Editors: In patients latently infected with Mycobacterium tuberculosis , immunosuppression significantly augments the risk of progression to active tuberculosis (TB) and TB is still one of the most frequent opportunistic infections worldwide. Prevention of TB in HIV-positive patients using the tuberculin skin testing (TST) followed by targeted preventive treatment is an effective strategy, but has thus far shown limited clinical success, in part due to the lack of a reliable test for latent TB infection (LTBI) 1. Interferon (IFN)-γ release assays (IGRAs) have shown great potential in the improvement of LTBI diagnosis, but the tests perform suboptimally in immunocompromised populations. We and others have previously shown that HIV-positive patients have high rates of indeterminate QuantiFERON®-TB Gold In-Tube test (QFT-IT) results and that this, at least in part, is due to low CD4 T-cell count 2–4. We and others have also shown that IFN-γ-inducible protein 10 (IP-10/CXCL-10) is an alternative biomarker may improve immunodiagnosis of M. tuberculosis infection. IP-10 is induced specifically and in large quantities upon in vitro stimulation of whole blood with M. tuberculosis -specific antigens. We have developed an IP-10 based test 5 and shown that the IP-10 test performs comparably to the QFT-IT in adult patients with intact immune function 6. We compared the sensitivity of an IP-10 based test with the QFT-IT for diagnosing M. tuberculosis infection in HIV-negative and HIV-positive patients with culture-confirmed active pulmonary tuberculosis (PTB). 300 patients newly diagnosed with PTB were recruited prospectively through the National Tuberculosis and Leprosy Programme (Mwanza, Tanzania). Blood was drawn for IGRA and HIV testing, and CD4 cell counts. Sputum was collected for microscopy and M. tuberculosis culture. Patients >15 yrs of age with a positive sputum culture result were enrolled. All HIV-positive patients were newly diagnosed in the study …

Interferon Gamma Release Assay in a 12-month-old BCG-Vaccinated Infant with Latent Tuberculosis Infection and IsolatedMycobacterium fortuitum: Table 1

The aim is to present a case of serial use of interferon-γ release assay (IGRA) test in the evaluation of an infant with a latent tuberculosis infection (LTBI) accompanied with a positive finding of Mycobacterium (M.) fortuitum in gastric juice. In addition to routine diagnostic evaluation (tuberculin skin test (TST), culture of gastric juice, chest X-rays), a 12-month-old female infant with a history of close family contact and a case of active tuberculosis was investigated with IGRA (QuantiFERON-TB Gold In-Tube, Cellestis, Carnegie, Australia). Tuberculin skin tests were positive. The first result of IGRA (on admission) was negative; the second (day 16) and third (day 57) results of IGRA were positive. M. fortuitum was cultured from gastric juice samples. Positive IGRA finding confirmed LTBI, and prophylaxis with isoniazid was administered. Since M. fortuitum does not express antigens that could be confirmed by the QuantiFERON-TB Gold In-Tube test, isolation of M. fortuitum could be interpreted as a possible contamination.

High prevalence of latent tuberculosis infection in dialysis patients using the interferon-gamma release assay and tuberculin skin test.

Patients in ESRD on hemodialysis with latent tuberculosis (TB) infection have 10 to 25 times the risk of reactivation into active disease compared with healthy adults. This study investigates the prevalence of latent TB infection in dialysis patients from a country with an intermediate burden of TB and its associated risk factors using the QuantiFERON-TB Gold in-tube test (QGIT) and the tuberculin skin test (TST). This was a prospective, cross-sectional study performed at a medical center in Taiwan on dialysis patients. Each patient underwent QGIT, two-step TST using 2 tuberculin units (TU) of PPD RT-23, a chest x-ray to exclude active TB, and an interview to determine TB risk factors. Ninety-three of 190 eligible patients were enrolled: 35 men and 58 women. 64.8% were vaccinated with the Bacille-Calmette-Guérin (BCG) vaccination. Overall, 34.4% were positive by QGIT and 10.8% were indeterminate. Using a 10-mm TST cutoff, 53.9% were positive. There was poor correlation between TST and QGIT at any TST cutoff criteria. There was a significant increasing trend of QGIT positivity with age in those younger than 70 years, and, conversely, a decreasing trend of TST reactivity with age. Significant risk factors for QGIT positivity included age and past TB disease. This study shows a high prevalence of latent TB infection in dialysis patients in a country with an intermediate burden of TB. QGIT in dialysis patients correlated better than TST with the risk of TB infection and past TB disease.

Valor de QuantiFERON-TB Gold Test in Tube en el diagnóstico de tuberculosis pulmonar y extrapulmonar

The Interferon-γ in vitro detection tests could be a useful tool in the diagnosis of active tuberculosis compared to Mycobacterium tuberculosis (MTB). The QuantiFERON-TB-Gold in Tube (QFG-IT) test was performed on the blood of 118 patients with active tuberculosis and the results compared with the tuberculin test. The QFG-IT test was positive in 94 cases (79.7%), negative in 17 (14.4%) and indeterminate in 7 (5.9%). A negative or indeterminate QFG-IT test was more common in older patients (P=0.017) and in cases with negative smear tests (P=0.041). The kappa agreement between the tuberculin and QFG-IT tests was 74.5% with a kappa value of 0.45 (SE:0.136). Thirteen of the patients studied were infected with HIV and the tuberculin was positive in 5 of the 12 cases (38.5%) in whom it was performed, with the QFG-IT being positive in 9/13 (69.2%). The QFG-IT test may be a useful complimentary tool to the tuberculin test in the diagnosis of tuberculosis.

Kinetics of the QuantiFERON®-TB Gold In-Tube test during treatment of patients with sputum smear-positive tuberculosis in relation to initial TST result and severity of disease

The QuantiFERON-TB Gold In-Tube test (QFN) measures interferon-gamma production in response to Mycobacterium tuberculosis antigens. Our aim was to assess the kinetics of the QFN and initial tuberculin skin test (TST) result in relation to severity of disease in a tuberculosis (TB) endemic area. Smear-positive TB patients (n = 71) were recruited at Gondar University Hospital, Ethiopia. The TST, QFN, CD4+ cell count and clinical symptoms (TB score) were assessed and followed up during treatment. From baseline to 7 months after treatment, there was a significant decrease in QFN reactivity (93.8% to 62.5% in HIV-negative/TB; 70.3% to 33.3% in HIV-positive/TB patients) down to a level comparable to a control group of blood donors (51.2%). The agreement between TST and QFN was poor in TB patients compared to healthy controls. A negative TST correlated to more advanced TB in contrast to a negative QFN test. We conclude that the QFN reactivity is significantly reduced at the end of treatment against active TB to the background level of healthy blood donors, and that the agreement between TST and QFN is poor including correlation to the severity of disease.

The Role of Chest CT Scanning in TB Outbreak Investigation

In TB outbreaks, detecting active cases is the key step in stopping transmission of the disease. The aim of this study was to evaluate the role of high-resolution CT (HRCT) scanning of the chest in the investigation of a TB outbreak that developed in a cohort of 92 soldiers in the South Korean army. Outbreak investigation, including tuberculin skin test (TST), QuantiFERON TB Gold In-Tube (QFT) test, and simple chest radiograph (CXR), was performed. For participants with any abnormal findings in these tests, HRCT scanning was done. Active pulmonary TB was diagnosed based on sputum studies or HRCT scan findings. In addition, participants with positive results in both TST and QFT were treated as having a latent TB infection (LTBI). TST and QFT were repeated in participants with a positive result in one of these tests. CXR was repeated in all participants at 3 and 6 months of follow-up. Eighty-seven participants completed the study protocol. Among them, 18 active TB cases were diagnosed. Nine of these had normal CXR, but had lesions that were suggestive of active TB on HRCT scan. Twenty-two participants with normal HRCT scans and positive results with TST and QFT at initial investigation were treated as LTBI. Among 13 participants with normal CXR and positive results in either TST or QFT, nine completed a 3-month investigation. All but one of nine participants revealed positive results in both tests. Inclusion of HRCT scanning in the outbreak investigation of TB may be helpful in differentiating active TB from LTBI more reliably. clinicaltrials.gov; Identifier: NCT00889759.

Serial testing of interferon-γ-release assays for the diagnosis of latent tuberculosis in hemodialysis patients

The performance of serial interferon-gamma-release assays (IGRAs) for the diagnosis of latent tuberculosis has not been studied in hemodialysis patients. The QuantiFERON-TB-Gold In-Tube test (QFT) and T-SPOT-TB test (TSPOT) were performed 1 year after initial testing at a hemodialysis center. Ninety-eight patients were included in the final analysis. Positive rates for the initial tuberculin skin test (TST), QFT and TSPOT were 26.5%, 43.9% and 58.2%, respectively. The follow-up QFT and TSPOT showed positive responses in 52.0% and 53.1%. Conversion rates of the QFT and TSPOT were 20.0% and 26.8%. Reversion rates of the QFT and TSPOT were 16.3% and 29.8%; however, they decreased to 0.0% and 4.8% in patients with a concordantly positive response at the initial TST. A group at high risk for latent tuberculosis increased the risk for the TSPOT conversion [odds ratio (95% confidence interval), 7.76 (1.27-47.40)] and showed a trend of increasing the risk for the QFT conversion [1.97 (0.45-8.71)]. Reversion of both the QFT [18.92 (2.01-178.65)] and TSPOT [6.16 (1.57-24.19)] occurred more frequently in the group at low risk. Both conversion and reversion of the IGRAs were associated with the risk for latent tuberculosis in hemodialysis patients. However, serial IGRAs results should be interpreted cautiously due to their high variability.

Diagnosis and follow-up of treatment of latent tuberculosis; the utility of the QuantiFERON-TB Gold In-tube assay in outpatients from a tuberculosis low-endemic country

BackgroundInterferon-gamma (IFN-γ) Release Assays (IGRA) are more specific than the tuberculosis skin test (TST) in the diagnosis of latent tuberculosis (TB) infection (LTBI). We present the performance of the QuantiFERON®-TB Gold In-tube (QFT-TB) assay as diagnostic test and during follow-up of preventive TB therapy in outpatients from a TB low-endemic country.Methods481 persons with suspected TB infection were tested with QFT-TB. Thoracic X-ray and sputum samples were performed and a questionnaire concerning risk factors for TB was filled. Three months of isoniazid and rifampicin were given to patients with LTBI and QFT-TB tests were performed after three and 15 months.ResultsThe QFT-TB test was positive in 30.8% (148/481) of the total, in 66.9% (111/166) of persons with origin from a TB endemic country, in 71.4% (20/28) previously treated for TB and in 100% (15/15) of those diagnosed with active TB with no inconclusive results. The QFT-TB test was more frequently positive in those with TST ≥ 15 mm (47.5%) compared to TST 11-14 mm (21.3%) and TST 6-10 mm (10.5%), (p < 0.001). Origin from a TB endemic country (OR 6.82, 95% CI 1.73-26.82), recent stay in a TB endemic country (OR 1.32, 95% CI 1.09-1.59), duration of TB exposure (OR 1.59, 95% CI 1.14-2.22) and previous TB disease (OR 11.60, 95% CI 2.02-66.73) were all independently associated with a positive QFT-TB test. After preventive therapy, 35/40 (87.5%) and 22/26 (84.6%) were still QFT-TB positive after three and 15 months, respectively. IFN-γ responses were comparable at start (mean 6.13 IU/ml ± SD 3.99) and after three months (mean 5.65 IU/ml ± SD 3.66) and 15 months (mean 5.65 IU/ml ± SD 4.14), (p > 0.05).ConclusionOnly one third of those with suspected TB infection had a positive QFT-TB test. Recent immigration from TB endemic countries and long duration of exposure are risk factors for a positive QFT-TB test and these groups should be targeted through screening. Since most patients remained QFT-TB positive after therapy, the test should not be used to monitor the effect of preventive therapy. Prospective studies are needed in order to determine the usefulness of IGRA tests during therapy.

Diagnosis of latent tuberculosis infection by using the QuantiFERON-TB Gold in-tube test in children whose household contact has contagious pulmonary tuberculosis disease

Diagnosis of latent tuberculosis infection by using the QuantiFERON-TB Gold in-tube test in children whose household contact has contagious pulmonary tuberculosis disease

Predictive factors for the indeterminate result on the QuantiFERON-TB Gold In-Tube test

Background: QuantiFERON-TB Gold In-Tube (QFT-G IT) test is recommended for screening of latent tuberculosis. However, this can reveal the indeterminate results, especially in the immunocompromised patients. Therefore, we investigated the predictive factors that can influence the indeterminate results on QFT-G IT. Methods: We performed a retrospective case-control study with 144 cases with the indeterminate results on QFT-G IT from October 2006 to March 2009 at Severance Hospital. The controls with the positive or negative results were selected by matching 1:1 with the case for date of QFTG IT assay. An indeterminate result was considered when the level in both the tuberculosis antigen and mitogen tube was less than 0.35 IU/ml, or the level in the nil tube was higher than 8.0 IU/ml. Through retrospective review of medical records, age, gender, total lymphocyte count at the QFT-G IT assay, underlying diseases, and medical conditions which can influence the immune function were collected as covariates. The predictive factors for the indeterminate results on QFT-G IT were assessed by multivariate logistic regression models. Results: Age and gender did not show the significant differences between case and control patients (p = 0.105 and 0.906). The percentage of patients with hematologic malignancy (19.4% vs. 11.1%, p = 0.049), chronic renal disease (22.2% vs. 9.7%, p = 0.004), and autoimmune disease (16.0% vs. 6.3%, p = 0.009) in the case group were the significantly higher than those in the control group. Also, the case group had the significantly higher percentage of steroid use (16.0% vs. 8.3%, p = 0.047) and solid organ transplantation (11.1% vs. 2.1%, p = 0.002) than the control group. The total lymphocyte count was the significantly lower in the case group than in the control group (median [interquartile range], 540 [220—1,030] vs. 1,370 [870—1,970], p < 0.001). In the final regression model, clinical factors associated with the indeterminate results were chronic renal disease (odds ratio [OR] 2.26, 95% confidential interval [CI] 1.03—4.94, p = 0.041), autoimmune disease (OR 3.99, 95% CI 1.65—9.66, p = 0.002), and solid organ transplantation (OR 5.06, 95% CI 1.30—19.73, p = 0.020). Conclusion: The patients with lower lymphocyte counts or immunosuppressive condition showed the higher possibility of the indeterminate results on QFT-G IT assay. Therefore, the combined assay such as tuberculin skin test and T-SOPT TB with QFT-G IT may be helpful to screen the latent tuberculosis in the patients with these conditions.

Latent Tuberculosis Diagnosis in Children by Using the QuantiFERON-TB Gold In-Tube Test

Latent Tuberculosis Diagnosis in Children by Using the QuantiFERON-TB Gold In-Tube Test

Comparison of tuberculin skin test and QuantiFERON-TB gold in tube test in patients with chronic inflammatory diseases living in a tuberculosis endemic population

We aimed to compare tuberculin skin test (TST) and QuantiFERON-TB gold in tube (QFT-IT) in patients with chronic inflammatory diseases living in a population where tuberculosis is endemic and BCG vaccination is routine. Twenty-five patients with rheumatoid arthritis (RA), 16 patients with spondilarthropathy (SpA) and 7 healthy volunteers were recruited in the study. Blood samples were collected for QFT-IT test followed by TST. TST was considered to be positive with an enduration of 5 mm and over in patients with RA and SpA. The cutoff point for TST for the healthy control (HC) was 10 mm. Median TST result of patients who were using immunosuppressive drugs was significantly lower than that of patients who were not [5 (14.5), 13.5 (9.5), respectively, P = 0.04]. Poor agreement between TST and QFT-IT was seen in patients with RA (kappa = 0.141) and in patients with SpA (kappa = 0.190). We found poor concordance between QFT-IT and TST in patients with chronic inflammatory diseases, and TST response was suppressed in patients treated with immunosuppressive drugs.

Performance of the tuberculin skin test and interferon-γ release assay for detection of tuberculosis infection in immunocompromised patients in a BCG-vaccinated population

BackgroundInterferon-γ release assay (IGRA) may improve diagnostic accuracy for latent tuberculosis infection (LTBI). This study compared the performance of the tuberculin skin test (TST) with that of IGRA for the diagnosis of LTBI in immunocompromised patients in an intermediate TB burden country where BCG vaccination is mandatory.MethodsWe conducted a retrospective observational study of patients given the TST and an IGRA, the QuantiFERON-TB Gold In-Tube (QFT-IT), at Severance Hospital, a tertiary hospital in South Korea, from December 2006 to May 2009.ResultsOf 211 patients who underwent TST and QFT-IT testing, 117 (55%) were classified as immunocompromised. Significantly fewer immunocompromised than immunocompetent patients had positive TST results (10.3% vs. 27.7%, p 0.001), whereas the percentage of positive QFT-IT results was comparable for both groups (21.4% vs. 25.5%). However, indeterminate QFT-IT results were more frequent in immunocompromised than immunocompetent patients (21.4% vs. 9.6%, p 0.021). Agreement between the TST and QFT-IT was fair for the immunocompromised group (κ = 0.38), but moderate agreement was observed for the immunocompetent group (κ = 0.57). Indeterminate QFT-IT results were associated with anaemia, lymphocytopenia, hypoproteinemia, and hypoalbuminemia.ConclusionIn immunocompromised patients, the QFT-IT may be more sensitive than the TST for detection of LTBI, but it resulted in a considerable proportion of indeterminate results. Therefore, both tests may maximise the efficacy of screening for LTBI in immunocompromised patients.