Utility of QuantiFERON TB-2G for tuberculosis contact investigations in public health services

OBJECTIVE: The objective of the present study was to examine the utility of QuantiFERON TB-2G (QFT) in tuberculosis contact investigations performed by a public health center. METHODS: Adachi City Public Health Center, Tokyo, started using QFT in its laboratory service in June, 2005. The results of QFT, as well as tuberculin skin tests (TSTs) performed in tuberculosis contact investigations in the 10 month period since then were here analyzed. QFT was carried out for 67 contacts two months after their last contact with the index case. TST was given simultaneously. RESULTS: Of the total of 67 contacts investigated during the period, 9 were positive for QFT, 5 were doubtful positive, and the remaining 53 were negative. Among 48 subjects tested with TST, 22 had strong reactions with erythema > or = 30 mm, out of which 4 were positive for QFT. In addition, there were 5 QFT-positives among the remaining 26 with weak tuberculin reactions. These 9 subjects with positive QFT were indicated for chemoprophylaxis. CONCLUSIONS: Adachi City Public Health Center is pioneering the application of new technology for detection of latent tuberculosis infection in contact investigations of the inhabitants. As expected from trial findings, QFT was shown to be a useful tool in a practical setting for the purpose of detecting TB infection, with greater accuracy than with TST, independent of the history of BCG vaccination. This approach can help avoid both over-diagnosis and under-diagnosis.     

中国东部地区结核菌素试验诊断结核病感染临界值的确定：基于人群的现况调查

目的 确定结核菌素试验的临界值来降低其诊断结核病潜伏性感染的假阳性。方法 测量受试者的FPG值,同时对受试者做结核菌素试验和QuantiFERON-TB（QFT）Gold In-Tube检测。以QFT为金标准,确定结核菌素试验（TST）试验的临界值。结果 共有5 405名参与者,其中1 104名（20.4%）QFT阳性。在5 405例患者中,PPD硬结直径为10.25 mm时诊断价值最高,其灵敏度为0.731,特异度为0.727。将受试者分为正常人、有糖尿病史患者、新确诊糖尿病患者,硬结直径分别在11.25 mm、10.25 mm和11.25 mm时诊断价值最高,其灵敏度和特异度分别为0.701、0.837、0.824和0.805、0.821、0.778。结论 本研究证实,以10~12 mm作为结核病潜伏性感染诊断的临界值可以大大提高结核菌素试验的特异性。     

Diagnosis of latent tuberculosis infection in candidates for kidney transplantation (comparison of two tests)

It is assumed that about 10% of individuals infected with Mycobacterium tuberculosis develop tuberculosis. The rate of tuberculosis in solid organ transplant recipients has been estimated to be 50-fold higher than in the general population. Candidates for solid organ transplantation are routinely screened for latent tuberculosis infection (LTBI). In this study we aimed to compare Tuberculin Skin Test (TST) with QuantiFERON-TB Gold In-Tube (QFT) for the detection of LTBI in candidate for kidney transplantation. Between October 2009 and November 2010, 64 candidates for kidney transplant who referred to the transplant clinic in Imam Khomeini Hospital, were enrolled in the study. Patients were screened for LTBI with both QFT and TST. Concordance between two test results and variables associated with test discordance were assessed. The mean age of patients was 38.5 years (range 16-65); female/male ratio was 26/38. Positive results were found in 21.9% and 21.9%, by TST and QFT, respectively. Four patients (6.3%) had indeterminate QFT. Overall agreement between QFT and TST was 75% (k=0.28 and P=0.028). BCG vaccination and past positive TST were not associated with positive QFT result (P=0.13 and P=0.09 respectively). Overall agreement between test results was fair. Comparison among test results showed that TST andQFT can be used interchangeably for latent TB screening in kidney transplant candidates. The decision to select QFT or TST will depend on the purpose of testing and resource availability.     

Validity of using tuberculin skin test erythema measurement for contact investigation during a tuberculosis outbreak in schoolchildren previously vaccinated with BCG

BACKGROUND: Few studies have examined the validity of administering tuberculosis control measures based on tuberculin skin test (TST) erythema measurement. The present study aimed to clarify the relationship between the erythema and the induration seen following TST and to evaluate the validity of diagnosing tuberculosis infection based on the erythema following TST in school-aged contacts who had been vaccinated with bacillus Calmette-Guérin (BCG) in infancy. METHODS: A 56-month longitudinal study from January 1999 through September 2003 followed 566 junior high school students in Kochi City who were contacts of an infectious tuberculosis case. To evaluate the diagnostic accuracy of the erythema and induration following TST of the contacts, false-positive and false-negative TST results were noted. RESULTS: The natural logarithm of the erythematous response size was linearly related to the induration size. When the size of the erythematous response was used to determine the presence of tuberculosis infection, the proportion of infected children increased with increasing exposure to the index case. When the TST results in the contact investigation were interpreted together with the change in the size of the erythematous response from that observed at the regular school-entry checkup, false positive test results were avoidable among the students who had a large erythematous response after the contact investigation TST, but whose response was only slightly larger than their erythematous response following the school-entry TST. Among the students whose TST results were negative, 1.9% developed tuberculosis. CONCLUSION: Both erythema and induration measurement were equally effective for identifying tuberculosis infection in schoolchildren vaccinated with BCG.     

Screening for tuberculosis infection using whole-blood interferon-gamma and Mantoux testing among Japanese healthcare workers.

OBJECTIVE: To examine the hypothesis that results of the QuantiFERON-TB Gold assay (QFT-G), a whole-blood test for detection of tuberculosis infection, are more significantly related to known risk factors for tuberculosis infection in healthcare workers (HCWs) who have received bacille Calmette-Guerin vaccine than are results of the Mantoux tuberculin skin test (TST). DESIGN: All HCWs (approximately 510) from a 370-bed general hospital in Tokyo where patients with and patients without tuberculosis are treated were invited to participate in the study. All study participants completed a questionnaire about their Mycobacterium tuberculosis infection risk factors as HCWs at the general hospital. They were then tested for LTBI by means of the QFT-G, followed by the TST. Statistical analyses were performed to compare results of each test with M. tuberculosis infection risk factors (age, length of employment in the healthcare industry, history of working with tuberculosis-positive patients in a tuberculosis ward or in the outpatient department of the hospital's tuberculosis clinic for more than 1 year, chest radiograph evidence of healed tuberculosis, history of performing bronchoscope procedures, and job classification), and for TST-positive HCWs, to compare the QFT-G result with the TST induration diameter. RESULTS: A total of 332 HCWs (95% of whom had been vaccinated with BCG) participated in the study, and 33 had positive QFT-G results, suggesting a prevalence of LTBI of 9.9%. Of 304 HCWs who underwent TST, 283 (93.1%) had an induration diameter of 10 mm or more. Multiple logistic regression analysis revealed that positive QFT-G results were significantly associated with age and with a history of working in a tuberculosis ward or an outpatient department of a tuberculosis clinic. TST results were not correlated with any of the tuberculosis infection risk factors we evaluated. CONCLUSIONS: Positive QFT-G results were closely associated with the presence of risk factors for LTBI in a hospital setting, suggesting that the QFT-G can detect LTBI in a population composed predominantly of BCG vaccinees. Because most HCWs worldwide have been vaccinated with BCG, the QFT-G offers a significant improvement over the TST in tuberculosis screening programs and minimizes unwarranted use of tuberculosis prophylaxis.     

Performance of an interferon-gamma release assay for diagnosing latent tuberculosis infection in children

Newly developed interferon-gamma release assays have become commercially available to detect tuberculosis (TB) infection in adults. However, little is known about their performance in children. We compared test results between the QuantiFERON-TB Gold test (QFT) and tuberculin skin test (TST) in young children living with pulmonary TB patients in Cambodia. Of 195 children tested with both QFT and TST, the TST-positive rate of 24% was significantly higher than the QFT-positive rate of 17%. The agreement between the test results was considerable (kappa-coefficient 0.63). Positive rates increased from 6% to 32% for QFT and from 15% to 43% for TST, according to the sputum smear grades of the index cases. The presence of Bacille Calmette-Guérin (BCG) scars did not significantly affect the results of TST or QFT in a logistic regression analysis. In conclusion, QFT can be a substitute for TST in detecting latent TB infection in childhood contacts aged 相似文献   

Preventing tuberculosis among HIV-infected persons: a survey of physicians' knowledge and practices

BACKGROUND: Guidelines exist for screening, diagnosing, and preventing tuberculosis (TB) among HIV-infected persons, but their application and utility are unknown. METHODS: We conducted a survey of knowledge and practices among 1,300 physicians in the San Francisco Bay area to assess their practices towards TB among HIV-infected persons. RESULTS: Of 630 respondents, 350 (56%) provided care for HIV-infected persons. Thirty-four percent of the respondents had seen the most recent guidelines for preventing tuberculosis among HIV-infected persons; 65% routinely provide information to HIV-infected patients about the risks of exposure to Mycobacterium tuberculosis; 39% provide annual tuberculin skin testing (TST) to HIV-infected patients without a history of a positive test; 86% knew that >/=5-mm induration is considered a positive TST result in HIV-infected persons; and 47% provide a 12-month regimen of chemoprophylaxis for HIV-infected persons who have a positive TST but not active tuberculosis. Physician specialty and experience with HIV-infected persons were not strongly correlated; experience was a better predictor of correct knowledge and practices. CONCLUSIONS: Many physicians were not aware of the standards of care for preventing tuberculosis among HIV-infected patients, even in a geographic area with a high prevalence of M. tuberculosis and HIV.     

Tuberculin skin test conversion among medical students at a teaching hospital in Rio de Janeiro, Brazil.

OBJECTIVE: To describe the cumulative incidence of and risk factors for tuberculosis (TB) infection among medical students. DESIGN: In 1999, a cohort study of medical students with negative results (induration < 10 mm) on tuberculin skin test (TST) was performed. Students who had undergone two-step testing in 1998 were retested. SETTINGS: University and teaching hospital and referral center for TB and acquired immunodeficiency syndrome, and the Health Sciences Building of the Medical School of the Federal University of Rio de Janeiro, Brazil. PARTICIPANTS: A sample of 618 consecutive medical students with negative TST results who had been tested 12 months before were approached. Information about sociodemographic characteristics, bacille Calmette-Guérin vaccination history, and potential exposures to TB was obtained using a standardized questionnaire. Four hundred fourteen (67%) students completed the study. Students were at two different levels of their training programs (juniors = no contact with patients; seniors = intensive contact with patients). RESULTS: Of 414 participants, 16 (3.9%; 95% confidence interval, 1.06% to 12.1%) had converted to a positive reaction after 1 year. In a multivariate logistic regression analysis, higher level of clinical training was confirmed to be an independent factor associated with TST conversion (odds ratio, 4.77; 95% confidence interval, 1.01 to 22.46; P= .048). CONCLUSION: Senior medical students are at increased risk of Mycobacterium tuberculosis infection in this setting. Therefore, a program of routine tuberculin skin testing and specific TB infection control guidelines are needed for this population.     

A survey of latent tuberculosis infection among laboratory healthcare workers in New York City.

OBJECTIVE: To determine the prevalence of positive tuberculin skin tests (TSTs), incidence of TST conversion, risk factors for positive TSTs, and history of active TB among HCWs in microbiology laboratories in New York City. DESIGN: Two-year survey from May 1999 to June 2001. SETTING: Nineteen microbiology laboratories. RESULTS: During the first year, interviews were conducted with 345 laboratory HCWs (mean, 18 HCWs per site; range, 2 to 51) to assess the prevalence of positive TSTs, but 3 (1%) could not recall their result and were excluded from further analyses. The mean age of the remaining 342 HCWs was 48 years; 68% (n = 233) were female, 54% (n = 183) received bacille Calmette-Guerin (BCG) vaccination, and 71% (n = 244) were foreign born. The prevalence of a positive TST was 57% (n = 196), but only 20% (n = 39) of the HCWs received isoniazid. The incidence of TST conversion in the second year of the study was 1% (1 of 108). Multivariate analysis identified age (odds ratio [OR] per year, 1.05; 95% confidence interval [CI95], 1.02-1.08), foreign birth (OR, 3.80; CI95, 1.98-7.28), BCG immunization (OR, 4.89; CI95, 2.72-8.80), and employment in a mycobacteriology laboratory (OR, 2.14; CI95, 1.25-3.68) as risk factors for a positive TST. Only one HCW had been treated for active TB. CONCLUSIONS: The prevalence of positive TSTs was high among laboratory HCWs, but the TST conversion rate was low. Higher rates of treatment for latent TB infection are desirable.     

Evaluation of results from occupational tuberculin skin tests--Mississippi, 2006

In October 2006, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation from a fire department in Mississippi. In June 2006, the fire department had administered two-step tuberculin skin tests (TSTs) and determined that nine firefighters tested positive for tuberculosis (TB) infection. Local investigation had identified no source of TB infection. The NIOSH evaluation was conducted to 1) determine whether TB transmission was occurring among department firefighters, 2) assess the accuracy of positive TST results, and 3) make recommendations regarding administration of future fire department TB-testing programs. This report describes the results of that evaluation, which indicated that all nine firefighters had false-positive TST findings, likely caused by errors in interpretation of the test results. These results highlight the importance of conducting TB testing only when indicated by TB risk assessment and following CDC guidelines to avoid errors in TST administration and interpretation that might result in unnecessary medical evaluation and follow-up.     

The effect of Bacille Calmette-Guérin vaccine on tuberculin reactivity in indigenous children from communities with high prevalence of tuberculosis

The Bacille Calmette-Guérin (BCG) vaccine is the most widely used vaccine in the world, however it may cause problems for the appropriate interpretation of the tuberculin skin test (TST). We assessed the diagnostic value of latent infection in vaccinated and unvaccinated indigenous children from communities that have a very high prevalence of adult tuberculosis (TB). A total of 997 children under 15 years old and classified in age groups (0-1.9, 2-5, 6-9 and 10-15 years old) were randomly selected and given TSTs using the Mantoux technique. TST induration values of vaccinated children (n=724) were compared with those of children unvaccinated (n=273). BCG vaccination was not an important cause of false-positive TST, except in communities with a low prevalence of active TB. In conclusion, the results suggested that a history of BCG vaccination on TST+ response after 10 years of vaccination was statistically insignificant but whether at earlier age TST+ reflects most probably the degree of exposure to TB cases than BCG vaccination should be clarified in the future.     

Predictors of tuberculin reactivity among prospective Vietnamese migrants: the effect of smoking

We investigated the prevalence and predictors of positive tuberculin skin test (TST) results among prospective Vietnamese migrants. We interviewed and medically screened 1395 Vietnamese people aged over 15 years who had applied to migrate to Australia. Approximately 44% of applicants had an induration of 10 mm or more, and 18.6% had an induration of 15 mm or more. A positive tuberculin skin test at 5 mm, 10 mm and 15 mm of induration cut-points was significantly associated with age (OR 1.01-1.02 per year) and duration of smoking (OR 1.03-1.12 per year). Smoking appears to be an important factor associated with increased susceptibility to mycobacterial infection. It is not yet clear whether the increased tuberculin reactivity associated with smoking reflects an increased risk of tuberculosis among these migrants.     

Prevalence of Tuberculin Skin Test Positivity in Clinical Population in New York City

The prevalence of latent tuberculosis infection (LTBI) in the various populations of New York City (NYC), a city with a high density of non-US-born persons, is unknown. We examined the prevalence of TST positivity in patients who received a tuberculin skin test (TST) between 1/2002 and 8/2004 at any of 10 NYC health department chest centers. A positive TST was defined as an induration reaction to tuberculin of ≥10 mm. In the study population of 41,022 individuals, prevalence of TST positivity was 24.4% (95%CI = 24.0, 24.8); four times higher among non-US-born persons than US-born (39.5% vs. 8.8%, Prevalence ratio (PR) = 4.5; 95%CI = 4.4, 4.6). Prevalence of TST positivity increased with age in both US and non-US-born persons. Persons from countries with a TB case rate >100/100,000 population had higher prevalence of TST positivity (47% vs. ≤39%), even after controlling for BCG (PR = 1.3, 95%CI = 1.2, 1.4). These findings provide insight into current prevalence of TST positivity in many immigrant populations and will help both clinicians and health departments to target patients for LTBI treatment.     

Guidelines for using the QuantiFERON-TB test for diagnosing latent Mycobacterium tuberculosis infection. Centers for Disease Control and Prevention.

Until 2001, the only test used to diagnose latent tuberculosis infection (LTBI) was the tuberculin skin test (TST). However, in 2001, a new test (QuantiFERON-TB or QFT; manufactured by Cellestis Limited, Carnegie, Victoria, Australia) that measures the release of interferon-gamma in whole blood in response to stimulation by purified protein derivative was approved by the Food and Drug Administration. This statement provides interim recommendations for using and interpreting QFT. As with TST, interpretation and indicated applications of QFT differ for persons according to their risk for LTBI and for developing tuberculosis (TB). This report provides guidance for public health officials, health-care providers, and laboratorians with responsibility for TB control activities in the United States in their efforts to incorporate QFT testing for detecting and treating LTBI. Regardless of the test used to identify LTBI, testing should be primarily targeted at diagnosing infected patients who will benefit from treatment.     

Quality Improvement of Tuberculosis Screening in Foreign-Born Patients

In the United States, a disproportionate percentage of tuberculosis (TB) cases occur in foreign-born persons. We implemented a performance improvement project to improve rates of screening for latent tuberculosis infection in a medical clinic. A questionnaire was developed to identify patients for tuberculosis screening, which was performed as a Tuberculin Skin Test (TST). Patients with positive skin tests underwent further testing. One hundred and sixty-five patients were screened, with 58 TSTs ordered and 36 placed. Twenty-seven patients returned to have the TST read with 12 positive. Eleven of these patients had chest X-rays, 2 revealing findings suggestive of active TB. This project identifies the importance of a standardized TB screening process for high-risk patients and identifies barriers to such a process.     

Risk for tuberculosis among children

Contacts of adults with tuberculosis (TB) are at risk for infection. Tests based on interferon-gamma (IFN-gamma) expression in response to Mycobacterium tuberculosis antigens may be more sensitive than the tuberculin skin test (TST). Risk for infection was assessed by using TST and an IFN-y-based assay (QuantiFERON Gold in Tube [QFT-IT] test) for 207 children in Nigeria in 1 of 3 groups: contact with adults with smear-positive TB, contact with adults with smear-negative TB, and controls. For these 3 groups, respectively, TST results were >10 mm for 38 (49%) of 78, 13 (16%) of 83, and 6 (13%) of 46 and QFT-IT positive for 53 (74%) of 72, 8 (10%) of 81, and 4 (10.3%) of 39 (p < 0.01). Most test discrepancies were TST negative; QFT-IT positive if in contact with TB-positive persons; and TST positive, QFT-IT negative if in contact with TB-negative persons or controls. TST may underestimate risk for infection with TB in children.     

Evaluation of the interferon-γ release assay in healthcare workers

Objectives An in vitro test for the diagnosis of latent TB-infection (LTBI) is now available that has the potential to replace the tuberculin skin test (TST). The new test measures the cell-mediated immune response to TB antigens. Little experience is currently available on the performance of the IGRA when testing HCW for LTBI. Therefore the aim of the study was to compare the IGRA with the TST in testing HCW for LTBI. Methods The medical staffs of three hospitals were simultaneously tested with TST (RT23) and IGRA (QFT). The study comprises 261 HCW, all exposed to active TB-patients. Information on gender, age, workplace, BCG vaccination and history of both TB and TST were collected using a standardised questionnaire. Results The TST was positive in 24.1% and the IGRA in 9.6% of the participants. Agreement between the tests was low in HCW with a BCG-vaccination. A history of an earlier TST was a risk factor for a positive TST but not for a positive IGRA. Out of 48 results positive in the TST but negative in the IGRA 97.8% might be explained by BCG vaccination or an earlier TST. A positive association between age and LTBI was observed for the IGRA but not for the TST results. Out of 25 positive results in the IGRA only 60% were recognized by the TST, too. The HCW with a positive IGRA and a negative TST had the same age (mean 49.1) as the HCW positive in both tests (mean 50.9), which was higher than the age of those negative in both tests (mean 38.8). Conclusions The data indicate that the IGRA should replace the TST in serial testing of HCW in high income, low incidence countries. The recommendations to use the IGRA in order to verify a positive TST only should be reconsidered.     

北京市昌平区某高校大学新生结核潜伏感染调查

目的 调查大学新生结核潜伏感染情况,以便采取预防性措施。 方法 2010年10月随机纳入北京市昌平区某高校入学新生TST≥10 mm的健康受试者420例,应用ELISPOT检测经抗原刺激后分泌IFN-γ的效应T淋巴细胞(即斑点形成细胞,SFCs)数量,并对ELISPOT阳性者进行为期3年的结核感染发病情况监测。 结果 ELISPOT检测LTBI总的阳性率为41.2%,在BCG接种(阳性率41.5%)和未接种(阳性率40.0%)中差异无统计学意义(χ²=0.064, P=0.447),在TST直径10~14、15~19和≥20 mm组间(37.6%、45.4%和64.3%)差异有统计学意义(χ²=8.408, P=0.015),173例未治疗的 ELISPOT+/TST+者经3年的ATB监测,发病率为0。 结论 北京市昌平区某高校大学新生LTBI比率高,但仅以ELISPOT和TST双阳性者为预防性治疗指标,尚不足够。     

Improving hand sensibility in vibration induced neuropathy: A case-series

Introduction

Results of systematic screening of healthcare workers (HCWs) for tuberculosis (TB) with the tuberculin skin test (TST) and interferon-γ release assays (IGRA) in a Portuguese hospital from 2007 to 2010 are reported.

Methods

All HCWs are offered screening for TB. Screening is repeated depending on risk assessment. TST and QuantiFERON Gold In-Tube (QFT) are used simultaneously. X-ray is performed when TST is > 10 mm, IGRA is positive or typical symptoms exist.

Results

The cohort comprises 2,889 HCWs. TST and IGRA were positive in 29.5%, TST-positive but IGRA-negative results were apparent in 43.4%. Active TB was diagnosed in twelve HCWs - eight cases were detected during screening and four cases were predicted by IGRA as well as by TST. However, the progression rate in IGRA-positive was higher than in TST-positive HCWs (0.4% vs. 0.2%, p-value 0.06).

Conclusions

The TB burden in this cohort was high (129.8 per 100,000 HCWs). However, the progression to active TB after a positive TST or positive IGRA was considerably lower than that reported in literature for close contacts in low-incidence countries. This may indicate that old LTBI prevails in these HCWs.     

Tuberculosis contact tracing among children and adolescents, Brazil

OBJECTIVE: To detect tuberculosis (TB) disease or infection among contacts of pulmonary TB patients. METHODS: Cross-sectional study in a Primary Healthcare unit in Rio de Janeiro (Brazil) with 184 child and adolescent contacts of pulmonary TB patients between March 1995 and March 1997. Subjects underwent clinical evaluation, chest radiographs, and tuberculin skin tests (TST); sputum smears were performed whenever possible. TB cases found were submitted to treatment and infected patients to chemoprophylaxis. Tuberculin converters, who tested positive for TST eight weeks after an initial negative result, received chemoprophylaxis. RESULTS: The sample included 98 boys and 86 girls; age ranged from 0 to 15 years; 26.9% were malnourished according to the Gomez criteria. Concerning the source of infection, 170 cases (92.4%) had household contacts, of which 66.5% were the child's parents. BCG vaccination was verified in 98.4% of children, and 14.7% of children had been revaccinated. Strong TST reactions were observed in 110/181 children. Seventy-six children (41.3%) were considered as infected by M. tuberculosis and 25 cases (13.6%) of TB were detected, of which seven (28%) were asymptomatic. There was greater occurrence of disease when the contact lived with more than one source of infection (p=0.02). CONCLUSIONS: The detection of TB disease and infection was high in the studied population. Contact control must be emphasized, for it allows for the diagnosis of TB in children who are still asymptomatic, in addition to identifying infected subjects who may profit from chemoprophylaxis.