QuantiFERON TB-2G Research Articles

Whole blood interferon‐γ assay for tuberculosis in children in Japan

Whole blood interferon-gamma assay QuantiFERON-TB2G (QFT-2G), which is a new specific method for diagnosing tuberculosis (TB), has been developed and used in the clinical field. The aim of the present study was to assess the usefulness of QFT-2G as an indicator, both for diagnosing childhood TB and for assessing therapeutic effectiveness. The subjects were 61 children introduced to the TB outpatient department for the first time between June 2004 and March 2006. QFT-2G, the tuberculin test and chest computed tomography (CT) were performed for all patients. Ten patients having typical characteristics of primary tuberculosis (PTB) on chest CT, and diagnosed as having tubercle bacillus infections, all had positive reaction on QFT-2G. Of seven patients who had no abnormalities on diagnostic imaging but who reacted positively on QFT-2G, one developed TB later, and no TB was detected over the period of observation in 44 patients with negative QFT-2G at their first consultation. Moreover, four patients with non-tuberculous acid-fast bacilli in which Mycobacterium avium or Mycobacterium gordonae was detected had negative reaction on QFT-2G. In addition, all 10 patients with positive reactions on QFT-2G in whom the subsequent course of the disease was observed had decrease on QFT after treatment. QFT-2G is a powerful tool with a wide application both in diagnosis and in assessment of treatment effectiveness in PTB.

Indeterminate results of QuantiFERON TB-2G test performed in routine clinical practice

The present authors assessed risk factors that can promote indeterminate results of QuantiFERON TB-2G (QFT-2G; Cellestis Ltd, Carnegie, Australia) tests. The subjects were 704 patients with suspected tuberculosis (TB) and latent TB infection between January 2005 and December 2007. The QFT-2G test and the tuberculin skin test (TST) were performed for all subjects. If the results of the QFT-2G test were indeterminate, the test was repeated within 1 month. In total, 72 (10.2%) patients showed indeterminate results on the QFT-2G test. Indeterminate results were due to positive control failure in 68 (88.9%) patients and negative control failure in four patients. The results of the TST were negative for 64 patients showing indeterminate results, the remaining eight patients showed a positive response to the TST. Indeterminate results were significantly associated with elderly and immunocompromised patients. Lymphocytopaenia and hypoalbuminaemia were significantly associated with indeterminate laboratory findings. When the QFT-2G test was repeated for all patients showing indeterminate results, 12 (16.7%) patients demonstrated determinate results on the subsequent test. Indeterminate results of the QuantiFERON TB-2G test under routine clinical practice are not infrequent. When scoring QuantiFERON TB-2G test results for elderly and immunocompromised patients, one must be careful because the possibility of obtaining determinate results may be low even if the test is repeated.

QuantiFERON TB-2G test for patients with active tuberculosis stratified by age groups

We evaluated the usefulness of the QuantiFERON TB-2G (QFT-2G) test and the tuberculin skin test (TST) in patients with active tuberculosis (TB) disease stratified by age in 10-year increments. Although the positive rate on TST was over 80% in younger patients aged < or =9 years, it decreased to 55% in patients of aged 70-79 years and 33% in patients aged over 80 years. However, the positive rate on QFT-2G test was over 80% for the age groups between 10-19 and 60-69 years, excluding younger patients aged < or =9 years. Furthermore, the rate was 79% in patients aged 70-79 years and 75% in patients over 80 years of age. The positive response rate of the QFT-2G test was significantly higher than that of the TST in patients over 50 years of age. The indeterminate result of the QFT-2G test increased with age and it is suggested that this result is concerned with the severity of underlying diseases in patients with active TB disease. Although the positive rate on QFT-2G test decreased with age in adults, it is thought to be a useful supportive diagnostic method for active TB disease compared to the TST, except in younger patients aged < or =9 years old.

Clinical evaluation of QuantiFERON TB-2G test in patients with healed pulmonary tuberculosis

We evaluated the response to the QuantiFERON TB-2G (QFT-2G) test in patients with healed pulmonary tuberculosis (TB) compared to the response in those with active pulmonary TB. The subjects were 208 patients with healed pulmonary TB and 155 patients with active pulmonary TB. The QFT-2G test results were analyzed by stratifying them into 5- or 10-year periods after the completion of antituberculosis treatment. Of the 208 patients with healed pulmonary TB, 63% had a positive tuberculin skin test (TST) and 34% had a positive QFT-2G test result. There was no significant difference in the positive response rate for the QFT-2G test, or in the positive test result rate for only the early secretory antigenin target 6-kD protein (ESAT-6) antigen, only the culture filtrate protein 10 (CFP-10) antigen, or both the ESAT-6 and CFP-10 antigens among any subgroups stratified by 5- or 10-year periods after the completion of antituberculosis treatment. The positive rate for the QFT-2G test was significantly higher in patients with active pulmonary TB (83%) than in patients with healed pulmonary TB (34%). Regarding the combined and separate responses to both the ESAT-6 and CFP-10 antigens, the positive response rate for both antigens was significantly lower in patients with healed pulmonary TB than in those with active pulmonary TB. Because many patients continued to show a positive response to the QFT-2G test even when a long period had passed after the completion of the antituberculosis treatment, it is suggested that, in patients with a previous history of TB, particular attention must be paid to the relapse of TB or reinfection with TB.

QuantiFERON TB-2G test for patients with active tuberculosis stratified by age groups

QuantiFERON TB-2G test for patients with active tuberculosis stratified by age groups

Clinical Evaluation of the T-SPOT.TB Test for Patients with Indeterminate Results on the QuantiFERON TB-2G Test

To evaluate the clinical utility of the T-SPOT.TB test for patients with indeterminate results on the QFT-2G test. Forty patients (10.6%) showed indeterminate results among 378 patients who underwent QFT-2G test because active TB disease was clinically suspected. T-SPOT.TB test was performed for these 40 patients before the initiation of antituberculous treatment. Forty patients (10.6%) were judged as showing indeterminate results on QFT-2G test because the positive control presented a lower IFN-gamma level. Elderly patients (68.2 versus 57.7) or immunocompromised patients receiving immunosuppressive treatments and patients with a decrease in lymphocyte count, serum protein and albumin were more frequently recognized in the patients with indeterminate results compared to those with determinate results on QFT-2G test. T-SPOT.TB test could clearly demonstrate the results in 26 of the 40 patients (65.0%) with indeterminate results of QFT-2G test; these were divided into six patients with positive results and 20 with negative results of T-SPOT.TB test. Elderly patients (73.5 versus 64.3) or patients with underlying diseases such as malignant disease and those receiving immunosuppressive treatment and patients with hyponutritional conditions were more frequently recognized in the patients with indeterminate results compared to patients with determinate results on both tests. We think it may be necessary to introduce T-SPOT.TB test to increase the diagnostic rate of TB disease including latent tuberculosis infection because indeterminate results of QFT-2G test might be further decreased using T-SPOT.TB test. Although 14 patients showed indeterminate results on both tests, the lymphocytes of these patients may not possess functional cytokine production activity.

Active Tuberculosis in Patients Undergoing Hemodialysis for End-stage Renal Disease: A 9-year Retrospective Analysis in a Single Center

Tuberculosis (TB) in patients undergoing hemodialysis (HD) for end-stage renal disease (ESRD) is commonly thought to be associated with a very poor prognosis. Moreover, it is difficult to diagnose. This report was designed to describe this condition and to determine the mortality rate and risk factors associated with mortality. In addition, the study evaluated the usefulness of QuantiFERON TB-2G((R)) (QFT-2G). Retrospective study Patients with confirmed TB admitted between January 2001 and May 2009 were retrospectively identified and enrolled. The clinical, radiological, and bacteriological data at the time of admission were recorded. A multivariate analysis was performed to identify the predictive factors for mortality. A total 19 TB patients (6 females; median age, 73 years) were included. TB occurred in most cases within 1.3 years from the initiation of dialysis. Most patients presented with fever (84.2%) and extrapulmonary TB (57.9%). The mortality rate within 24 weeks of the initiation of TB treatment was 36.8%. The factors associated with mortality were: a short duration of dialysis (HR 8.86, 95% CI 1.03-75.7, p=0.04), and underweight (HR 10.88, 95% CI 1.28-92.6, p=0.02). The sensitivity of QFT-2G, acid-fast smear, and polymerase chain reaction was 50, 80, and 88.2% respectively. These data indicate a high incidence of TB in the early stages of HD and a high mortality rate among these patients. The clinical utility of QFT-2G was found to be limited. Hypoalbuminemia might therefore be related to either indeterminate or negative results of QFT-2G.

Transitional changes in T-cell responses to Mycobacterium tuberculosis-specific antigens during treatment

Currently, there is no available test for monitoring the clinical effect of active tuberculosis (TB) disease treatment. Therefore, we studied the usefulness of two commercial IFN-gamma assays (QuantiFERON TB-2G (QFT-2G) and T-SPOT.TB tests) for monitoring clinical efficacy. The subjects were 40 patients with active TB disease. These two commercial IFN-gamma assays were carried out every three months during active TB disease treatment. While the positive response rate of QFT-2G test significantly decreased from 83% at treatment initiation to 58% at treatment completion, that of T-SPOT.TB decreased from 90% at treatment initiation to 63% at treatment completion. Although there was a significant decrease in patients with TB infection showing positive responses for ESAT-6 only or CFP-10 only antigens on both IFN-gamma assays, there was no significant decrease in patients showing positive responses for both ESAT-6 and CFP-10 antigens on both IFN-gamma assays. On both QFT-2G test and T-SPOT.TB test, the mean values of the IFN-gamma levels in the pre- and post-treatment responses showed significantly decreased responses to CFP-10. On the other hand, smear conversion results of clinical specimens were obtained in all patients at treatment completion. Antituberculous treatment induced a significant decrease in T-cell responses to separate ESAT-6 and CFP-10 antigens as measured by both IFN-gamma assays. Although IFN-gamma assays might be later than smear conversion results of clinical specimens, the quantitative responses especially to CFP-10 may be one of the useful monitoring markers of clinical efficacy for active TB disease treatment.

Effects of prophylaxis on QuantiFERON TB-2G responses among children

To study the effect of treatment of latent tuberculosis infection (LTBI) on QuantiFERON TB-2G (QFT-2G) test results. QFT-2G was used for a contact investigation in a junior high school and those positive or doubtful positive (TB Antigen-Nil response > or = 0.1 and < 0.35 IU/ml) were indicated for treatment of LTBI with INH. All subjects who completed treatment of LTBI were re-tested with QFT-2G approximately 1 month after completion of treatment and a subset were again re-tested 8 to 11 months after the completion of treatment. The levels of IFN-gamma response in each QFT-2G test were compared. Initially, 43 subjects (28 QFT-2G positive and 15 doubtful positive) were indicated treatment of LTBI, and 41 (95%) completed 6-months treatment. These 41 subjects were re-tested with QFT-2G approximately 1 month after the completion of treatment. Among 28 pre-treatment positives, 19 remained positive, 6 became doubtful positive, and 3 reverted to negative. Among 13 pre-treatment doubtful positives, 1 converted to positive, 5 remained doubtful positive, and 7 reverted to negative. The QFT-2G responses after the completion of treatment significantly declined compared with the pre-treatment level (geometric means; before treatment ESAT-6: 0.30 IU/ml, CFP-10: 0.09 IU/ml, after treatment ESAT-6:0.18 IU/ml, CFP-10: 0.05 IU/ml, dependent t-test; ESAT-6: p = 0.020, CFP-10: p = 0.005). At 8 to 11 months after the completion of treatment, 30 randomly selected subjects received the third QFT-2G test. Among 19 positives at the completion of treatment, 14 remained positive, 4 become doubtful positive, and 1 reverted to negative. Among 8 doubtful positives at completion of treatment, 4 converted to positive, 3 remained doubtful positive, and 1 reverted to negative. A further decline of QFT-2G responses was not observed. Three subjects negative at the completion of treatment were re-tested and remained negative at the third test. QFT-2G responses significantly declined after the treatment of LTBI, despite the rate of reversion in QFT-2G being low. This low reversion rate suggests QFT-2G would not be useful as a marker to evaluate the success of treatment for LTBI. However, the finding that QFT-2G responses significantly decline after the treatment of LTBI suggests the possibility that this decline could be used as a marker of the susceptibility of the infective M. tuberculosis strain to the prophylactic drug used. The outbreak investigation has been carried out for over two years, and none of 229 students who were TST positive, but QFT-2G negative and because of this result not indicated treatment of LTBI, have developed TB, suggesting that QFT-2G reflects TB infection more accurately than the TST, even in school children.

Clinical Utility of the QuantiFERON TB-2G Test for Elderly Patients With Active Tuberculosis

To evaluate the response to the QuantiFERON-TB-2 Gold (QFT-2G) test (Cellestis Ltd; Carnegie, VIC, Australia) in elderly patients with active tuberculosis (TB) to determine whether the QFT-2G test might be a feasible method for diagnosing TB infection in this group of patients. The subjects were 30 elderly patients with active TB and 100 younger patients with active TB. The QFT-2G test results were analyzed in relation to combined and separate responses to early secretory antigenic target 6-kD (ESAT-6) protein and culture filtrate protein 10 (CFP-10) antigens. Of the 30 elderly patients with active TB, 27% had a positive tuberculin skin test (TST) result and 77% had a positive QFT-2G test result. Of the 100 younger patients with active TB, 70% had a positive TST result and 87% had a positive QFT-2G test result. Although there was no significant difference between the two patient groups in the positive rate for the QFT-2G test results (p = 0.185), there was a significant difference in the rates of positive TST results between the elderly and younger patients (p = 0.012). The positive test result rate for both ESAT-6 and CFP-10 antigens in the elderly patients (17%) was significantly lower than that in younger patients (37%; p = 0.038). There was an indeterminate result for the QFT-2G test in five elderly patients, and this might have been related to the presence of lymphocytopenia due to underlying disease. A negative result on the QFT-2G test was detected in two elderly patients, and this might have been related to the severity of the active TB. We confirmed that the QFT-2G test might be a more useful method of diagnosing TB infection than the TST for elderly patients if peripheral lymphocyte counts have been preserved.

Quantiferon TB-2G among nurses with a history of working in our tuberculosis ward

To investigate the infection rate of tuberculosis among nurses with a history of working in our hospital's tuberculosis ward (TW). We measured interferon gamma levels in 50 nurses who had worked in our TW, and evaluated the infection rate among these nurses before (I) and after (II) the use of our hospital's tuberculosis infection control manual. The infection rate including probable infection was 6/50 (12.0%) in all TW nurses. The infection rate in the group I was 17.6%, but that in group II was 0%. Our hospital's tuberculosis infection control manual was effective for decreasing the infection rate, despite a high rate of infection in group I.

Usefulness of the QuantiFERON TB-2G Test for the Differential Diagnosis of Pulmonary Tuberculosis

We prospectively evaluated the usefulness of the QuantiFERON TB-2G (QFT-2G) compared to that of tuberculin skin test (TST) as a supportive method of diagnosing pulmonary tuberculosis (TB) without invasive examinations. The subjects were 90 patients who required differentiation of pulmonary TB clinically and for whom a definitive diagnosis could not be obtained after admission. The final clinical diagnosis of TB infection in 28 patients and non-TB infection in 62 patients was established using bronchoscopic procedures. In patients with TB infection, the positive response rate on QFT-2G (79%) was significantly higher than that on TST (57%). The QFT-2G negative rate (5%) was significantly lower than that on TST (48%) in patients with non-TB infection. For QFT-2G test, there was a positive response in 25 patients, a negative response in 49, and indeterminate findings in 16. Of the two patients with a false-negative result on QFT-2G, one had pulmonary TB during immunosuppressive treatment and one had pulmonary tuberculoma. Of the three non-TB patients with a positive result on QFT-2G, two had pneumonia and one had pulmonary mycosis. Four TB patients with an indeterminate result on QFT-2G included two elderly patients and two immunocompromised patients. We could confirm the usefulness of the QFT-2G test compared to TST in patients requiring a differential diagnosis between pulmonary TB and other pulmonary diseases in this series. Therefore, we recommend the QFT-2G test as one of the useful noninvasive diagnostic examinations for pulmonary TB.

小児におけるＱｕａｎｔｉＦＥＲＯＮ ＴＢ‐２Ｇの特異度に関する検討

Objective: To examine the specificity of QuantiFERON®TB-2G (QFT) in tuberculosis contact investigations of children. Methods: A schoolgirl was diagnosed with smear-positive pulmonary tuberculosis. To determine the extent of tuberculosis infection among contact schoolchildren, tuberculin skin tests were performed on 75 children enrolled in the school. All the children had been vaccinated with BCG at least once. The QFT test was then given to the 68 children who had tuberculin reactions including erythema larger than 10㎜ in diameter. Written informed consent was obtained from a parent of each child. Results: The number of infected subjects was 22 based on tuberculin skin test results. Of the 68 contacts, 1 was positive for QFT, 2 were doubtful positive, and the remaining 65 were negative. During the 2-year follow-up, none of the children developed tuberculosis. Specificity was 95.6%. Conclusions: It was confirmed that the additional use of QFT would reduce the number of indications for chemoprophylaxis cases. The current criteria for the indication of chemoprophylaxis based on a strong tuberculin reaction are considered unreliable, causing many subjects with strong reactions to be given unnecessary preventive medications.

Long-term Follow-up of the QuantiFERON TB-2G Test for Active Tuberculosis Disease

To evaluate transitional changes in QuantiFERON TB-2G (QFT-2G) test results in the serial testing on the same patients and to reevaluate the optimal threshold of positive response of QFT-2G test as a cure of TB infection. We prospectively investigated transitional changes of QFT-2G test results in 22 patients with active tuberculosis (TB) over three years after the initiation of treatment with antituberculosis drugs. Treatment using antituberculosis drugs was performed for six months in all patients. The positive rate of QFT-2G test results decreased 50% at the treatment completion. Thereafter, although the positive rate of QFT-2G test results has been decreased 45% six months later even if treatment was finished, it decreased slightly to 41% two years later and 36% three years later. If the cut-off value was situated below 50% (IFN-gamma level three years later/ IFN-gamma level of baseline peak value), we could judge the conversion of QFT-2G test in most cases except for two cases three years after the initiation of antituberculosis treatment through this study. It may be difficult to monitor markers in the cure of TB infection using QFT-2G tests. The cut-off level for a positive response on QFT-2G test may need to be reconsidered when the test is used to monitor the response of active TB to therapy.

Clinical evaluation of QuantiFERON TB-2G test for immunocompromised patients

The usefulness of the tuberculin skin test (TST) and the QuantiFERON TB-2G (QFT-TB) test were compared in immunocompromised patients. The subjects consisted of 252 immunocompromised patients who were clinically suspected of tuberculosis (TB) infection between April 2005 and December 2006. Regarding the underlying diseases, 74 subjects had malignant diseases, 72 were undergoing immunosuppressive treatment, 52 had diabetes mellitus, 50 had chronic renal failure and four had HIV infection. While the positive rate of the QFT-TB test for the diagnosis of TB infection (TB disease or latent TB infection) was 78.1%, that of TST for TB infection was 50.0%. The QFT-TB test was significantly better than TST. However, 32 (13%) patients had an indeterminate QFT-TB result. Indeterminate findings were significantly more frequent in patients receiving immunosuppressive treatment (28%), especially with lymphocytopaenia in the peripheral blood, than in those who had other underlying diseases. While TST-positive and QFT-TB test-negative results were recognised in immunocompromised patients with bacille Calmette-Guérin vaccination or nontuberculous mycobacterial disease, TST-negative and QFT-TB test-positive results were recognised in immunocompromised patients with a past history of TB infection. It was concluded that the QuantiFERON TB-2G test is a more useful diagnostic method for tuberculosis infection than tuberculin skin test for immunocompromised patients suspected of tuberculosis disease. However, because the results of the QuantiFERON TB-2G test show an indeterminate response for patients receiving immunosuppressive treatment, especially for those with lymphocytopaenia due to severe underlying diseases, care must be taken in the interpretation of the QuantiFERON TB-2G test for these patients.

Usefulness of QuantiFERON TB-2G, a Diagnostic Method for Latent Tuberculosis Infection, in a Contact Investigation of Health Care Workers

To evaluate the usefulness of QuantiFERON TB-2G (QFT-2G) for detecting latent tuberculosis infection (LTBI) in a contact investigation of health care workers. The investigated subjects were 190 subjects among the health care workers who were examined between January 2005 and June 2006. Background information, including a past history of tuberculosis (TB) or tuberculin skin test (TST) or BCG vaccination, and contact score (infectivity x contact duration) were investigated. The TST and QFT-2G test were performed on all subjects. In 109 subjects with a negative TST history, the TST results were converted to positive in 38 subjects. While the TST was positive in 48 subjects (25%), the QFT-2G test was positive in only five subjects (3%). The correlation of the QFT-2G with TST results was not significant. There was no relationship between contact score and the TST result. Twenty-nine subjects had TST positive responses (22%), but there were no QFT-2G positive responses in subjects with a mild contact score. Sixteen subjects had TST positive responses (31%), but two subjects showed positive QFT-2G results (4%) in the moderate contact score group. However, the positive response rate of the TST and QFT-2G test was the same percentage in the severe contact score group (33%). The QFT-2G test showed a significant relationship with the contact score when compared with the TST. If the subjects with LTBI in the moderate contact score group were selectively excluded, the contact investigation in the mild contact score group may not be necessary. If there would have been many subjects with the QFT-2G positive responses in the moderate contact score group, we think that the QFT-2G test must be performed even in the mild contact score group.

An indeterminate QuantiFERON TB-2G response for miliary tuberculosis, due to severe pancytopenia

We report the case of a 56-year-old man with miliary tuberculosis whose response to the QuantiFERON (QFT) TB-2G (Cellestis; South Melbourne, Australia) test was indeterminate due to pancytopenia (lymphocytopenia). The patient had severe lymphocytopenia due to either the miliary tuberculosis or immunosuppressive treatment with a corticosteroid; for the 2 years before admission, he had received corticosteroid treatment for Behçet's disease. The lymphocytopenia was also a complication of multiple organ failure and disseminated intravascular coagulation. A chest radiograph and computed tomography (CT) scan revealed a miliary shadow. After intubation performed because of acute respiratory failure, Mycobacterium tuberculosis was cultured from bronchoalveolar lavage fluid. We made a clinical diagnosis of miliary tuberculosis because M. tuberculosis was demonstrated in both lung and bone marrow specimens. However, immunologically, the tuberculin skin test was negative and the QFT-TB 2G test response was indeterminate, based on the CDC guideline. Although the QFT-TB 2G test has been used recently as a supportive method for the diagnosis of active tuberculosis, care must be taken in judging the condition of a patient with lymphocytopenia caused by severe underlying disease or immunosuppressive treatment. This patient was treated with antituberculous drugs 3 days after admission, but he died of multiple organ failure 6 days after admission.

Clinical Reevaluation of the QuantiFERON TB-2G Test as a Diagnostic Method for Differentiating Active Tuberculosis from Nontuberculous Mycobacteriosis

We reevaluated the usefulness of a whole-blood interferon-gamma enzyme-linked immunosorbent assay (QuantiFERON TB-2G [QFT-TB]; Cellestis) in obtaining a differential diagnosis between active tuberculosis (TB) and nontuberculous mycobacteriosis (NTM). The subjects were 50 healthy volunteers, 50 patients with active TB, and 100 patients with NTM who satisfied the diagnostic guidelines of the American Thoracic Society from April 2005 through June 2006. The tuberculin skin test (TST) and the QFT-TB test were performed for all subjects. The QFT-TB test was performed every 2 months. Of the healthy volunteers, 64% had a negative TST result and 94% had a negative QFT-TB test result. Of the patients with active TB, 64% had a positive TST result and 4% had a negative QFT-TB test result. Of the patients with pulmonary Mycobacterium avium complex disease, 60% had a positive TST result and 7% had a positive QFT-TB test result. The QFT-TB test had a mean sensitivity of 86% and a mean specificity of 94%. The QFT-TB test results for patients with active TB transiently decreased during treatment involving antituberculous drugs. The rate of positive QFT-TB test results was 86% at the initiation of treatment, 48% 6 months later, and 33% 12 months later. We confirmed that the QFT-TB test is a useful diagnostic method for differentiating active pulmonary TB from NTM, compared with the TST. However, because it is possible that the effect of the QFT-TB test may be long lasting after treatment and may not be resolved over time, even with treatment, as in this study, it may not provide any level of certainty regarding cure of infection.