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.     

Increase in tuberculin skin test converters among health care workers after a change from Tubersol to Aplisol

BACKGROUND: Comparability of the 2 commercially available tuberculin skin testing (TST) preparations, Aplisol (Parkdale Pharmaceuticals, Inc, Rochester, MI) and Tubersol (Aventis Pasteur, Inc, Swiftwater, PA), remains uncertain, particularly in groups that undergo repeated testing, such as health care workers. METHODS: Data from the annual tuberculosis screening program for health care workers at the Kennedy Krieger Institute in Baltimore, Maryland, were analyzed. Conversion rates during 1997-2003 in workers screened with Tubersol (n = 8897 screenings) were compared with 1203 workers who underwent screening with Aplisol in 2004. Repeat testing with Tubersol was examined in those who converted in 2004 with Aplisol. RESULTS: Annual TST conversion rates ranged from 0.3% to 0.9% between 1997 and 2003 using Tubersol. After switching to Aplisol in 2004, the TST conversion rate significantly increased to 2% (P < .001). Among 24 health care workers who were converters with Aplisol in 2004, only 6 of 23 (26%) were converters on repeat testing with Tubersol (1 declined retesting). None of the apparent converters (n = 24) had radiographic evidence of Mycobacterium tuberculosis infection, and there was no epidemiologic evidence of transmission. Reclassification based on Tubersol testing in 2004 resulted in conversion rates comparable with previous years. CONCLUSION: We conclude that the change from Tubersol to Aplisol resulted in falsely elevated conversion rates. Our results support the guidelines from the Centers for Disease Control and Prevention recommendations that 1 product should be used consistently in populations undergoing periodic testing.     

Effect of anti-tuberculosis treatment on the tuberculin interferon-gamma response in tuberculin skin test (TST) positive health care workers and patients with tuberculosis.

SETTING: Public hospital, Victoria, Australia. OBJECTIVE: To evaluate the effect of multidrug treatment and isoniazid (INH) chemoprophylaxis on the tuberculin interferon-y assay (QIFN) in 19 patients with culture-confirmed Mycobacterium tuberculosis and 119 health care workers (HCWs) with tuberculin skin tests (TST) > or =15 mm. DESIGN: Patients with M. tuberculosis were treated with standard medication and tested with QIFN at diagnosis and at regular intervals over a 12-month period. All HCWs, 59 (50%) of whom were prescribed INH chemoprophylaxis, were tested with QIFN at baseline, 2, 4, 6 and 12 months. RESULTS: QIFN results in patients with tuberculosis were consistent and reproducible. At the initial time point QIFN assays were positive for M. tuberculosis in 67%, and once positive, the QIFN assay remained so over the 12-month period. In the HCWS, initial QIFN assays were positive in 73 (61%). During the 12-month study, 91 HCWs had a QIFN assay on at least two occasions. The overall reproducibility between tests was fair (kappa statistic = 0.45), and was little affected by administration of INH. CONCLUSION: These data suggest that although the QIFN assay is generally positive in patients with proven tuberculosis, it does not provide clinically useful information during the first 12 months of treatment with multidrug chemotherapy or INH chemoprophylaxis.     

Comparison of the tuberculin skin test and the quantiferon test for latent Mycobacterium tuberculosis infections in health care workers in Turkey

The aim of this study was to compare the efficacy of the tuberculin skin test (TST) and the quantiferon test (QFT) for detecting latent tuberculosis infection (LTBI) in health care workers (HCWs). Seventy-six participants who were working in Duzce University Hospital, where tuberculosis patients were being treated, were included in the study. TST was performed according to the Mantoux technique. QFT was performed in accordance with the manufacturer's instructions. A positive TST result was defined as an induration diameter of > or = 15 mm. TSTs were positive in 41 of 76 participants (53.9%) and QFT was positive in 65 of 76 participants (85.5%). There was a significant difference between the numbers of QFT-positive and TST-positive cases (P=0.02). When the induration diameter of TST was > or = 20 mm, QFT positivity was 100%. Multivariate analysis revealed that there was a significant correlation between the percentage of patients with QFT positivity and the induration diameter of TST (P=0.009). QFT thus seems to be more effective for LTBI diagnosis than TST. However, large-scale trials including quantitative measurement of QFT in subgroups taking into account the division where HCWs are employed and the different results of TST might clarify the usefulness of QFT in LTBI diagnosis.     

A tuberculin skin test survey among Afghan children in Kabul.

SETTING: Kabul, Afghanistan, October to November 2000. OBJECTIVE: To determine the prevalence and the average annual risk of infection with Mycobacterium tuberculosis (ARTI). METHODS: A cluster sampling method was selected to carry out the survey. Sub-divisions of Kabul's districts were chosen, and door-to-door visits were carried out to register the children. The prevalence of tuberculous infection was determined using a cut-off point to denote infection and mixture analysis. The average ARTI was derived algebraically from the prevalence estimates. RESULTS: The tuberculin skin test was administered and read in 89% of registered children. Utilising a cut-off point of > or = 8 mm in duration, the estimated prevalence of tuberculous infection was 4.3% and the calculated average ARTI was 0.61%. Using mixture analysis, the average ARTI was estimated to be 0.34% (95% credibility interval 0.23-0.54). This indicates a substantial decrease from the estimated ARTI of 2.55% calculated in the 1963 survey. CONCLUSIONS: There has been a large decrease in the risk of tuberculous infection in Kabul since the last assessment. The adverse situation in the past decades does not appear to have severely affected the epidemiological situation.     

Comparison of the interferon- gamma release assay and the tuberculin skin test for contact investigation of tuberculosis in BCG-vaccinated health care workers

Health care workers are at increased risk of Mycobacterium tuberculosis infection. The tuberculin skin test (TST) is frequently false positive in BCG-vaccinated health care workers. QuantiFERON-TB GOLD (QFT-G) is a sensitive and specific interferon-gamma release assay unaffected by BCG vaccination. This study compared TST and QFT-G in the diagnosis of latent TB infection in BCG-vaccinated health care workers. 39 health care workers exposed to a smear-positive TB patient were enrolled. Initial TST was positive in 33 (84.6%) cases, but only 4 (10.2%) cases using QFT-G. TST conversion occurred in 2/6 (33.3%), compared to 4/32(12.5%), cases using QFT-G. A higher proportion of QFT converters was associated with intimate contact, although not reaching statistical significance. Face-to-face contact >1 h was significantly associated with QFT-G conversion >or=0.7 IU/ml (OR 8.63, 95%CI 1.08-69.07, p=0.04). Agreement between TST and QFT-G was 18.0%, (kappa: -0.03). Concordance between TST and QFT (>or=0.35 IU/ml) conversion was 40.0%(kappa=-0.40), and 60.0%(kappa=0.00) if QFT >or=0.7 IU/ml was used. Agreement increased with increasing TST cut-offs. TST is not useful in contact investigation among BCG-vaccinated health care workers, in an area with intermediate burden of TB. QFT may provide additional information for the diagnosis and strategic management of preventive treatment of LTBI in BCG-vaccinated health care workers in a country with intermediate burden of TB.     

Prevalence and risk factors associated with tuberculin skin test positivity among household contacts of smear-positive pulnionary tuberculosis cases in Umerkot, Pakistan.

STUDY POPULATION AND SETTING: Household contacts of acid-fast bacilli (AFB) sputum smear-positive tuberculosis patients in the Umerkot Taluka, Sindh, Pakistan. OBJECTIVE: To estimate the prevalence of and identify risk factors associated with tuberculin skin test (TST) positivity among household contacts of acid-fast bacilli (AFB) sputum smear-positive pulmonary tuberculosis cases. DESIGN: A cross-sectional study of household contacts of AFB sputum smear-positive tuberculosis cases, registered at the Umerkot Anti-Tuberculosis Association clinic from August 1999 to September 1999. The contact's Mycobacterium tuberculosis infection status was assessed using TST. On the day of the TST, a pre-designed questionnaire was administered to collect data on putative risk factors for TST positivity among contacts. The data were analysed using a marginal logistic regression model by the method of generalised estimating equations (GEE) to determine risk factors independently associated with TST positivity. RESULTS: The prevalence of TST positivity among household contacts of AFB sputum smear-positive index patients was 49.4%. The final multivariate GEE model showed that contact's age and sleeping site relative to the index case, the intensity of the index case's AFB sputum-smear positivity and the contact's BCG scar status were independent predictors of TST positivity among household contacts of AFB sputum smear-positive index cases. CONCLUSIONS: The results suggest that the household contacts of AFB sputum smear-positive tuberculosis patients in a poor neighbourhood of rural Sindh had a high prevalence of M. tuberculosis infection as determined by TST. Poor housing conditions seem to contribute to the spread of M. tuberculosis infection. Early diagnosis of pulmonary TB through evaluation of TST-positive household contacts, followed by appropriate therapy, may prevent further spread of M. tuberculosis infection. We recommend an awareness programme to prevent household contacts from acquiring M. tuberculosis infection from smear-positive pulmonary TB cases.     

Tuberculin skin test conversion rate in dental health care workers-results of a prospective study.

OBJECTIVES: The tuberculin skin test conversion rate over 12 months in dentists, dental hygienists, and dental assistants was assessed in 3 US-Mexico border counties of Texas in which reported tuberculosis rates were high compared with the rates for Texas and the United States. METHODS: Tuberculin skin tests were administered to 284 subjects and repeated on nonreactors 12 months later. Participants also completed self-administered questionnaires. RESULTS: The baseline positive tuberculin skin test prevalence was 4. 6%. Nonreactors were more likely to have been born in the United States (P <.001). The tuberculin skin test conversion rate over 12 months was 1.7%. CONCLUSION: Results indicate a need for heightened awareness of tuberculosis transmission and annual surveillance by dental health care workers, as recommended by the Centers for Disease Control and Prevention.     

Dramatic decrease in tuberculin skin test conversion rate among employees at a hospital in New York City

Background: The Centers for Disease Control and Prevention recently issued updated guidelines for preventing the transmission of tuberculosis in health care facilities. Many recommendations, including the use of high-efficiency particulate air filter respirators, are expensive to implement and of unproven efficacy. We therefore reviewed the tuberculin skin test conversion rate among our employees from 1991 to 1993, before introduction of high-efficiency particulate air filter respirators. During this period, several other improvements in tuberculosis control were implemented.Methods: Employee tuberculin test conversion rates were reviewed by 6-month interval from 1991 to 1993.Results: Throughout the study period, several tuberculosis control measures were implemented, including early isolation of patients with suspected cases of tuberculosis in rooms with negative-pressure ventilation, placement of germicidal UV light fixtures into patient rooms and common areas, and use of Technol shields (Technol, Inc., Fort Worth, Texas) (1991), particulate respirators (1992), and dust-mist-fume respirators (1993). With these improvements, the conversion rate among employees fell from 20.7% in the first 6 months of 1991 to 5.8% in the latter half of 1993.Conclusions: The rate of skin test conversion among our employees decreased before introduction of high-efficiency particulate air filter respirators. This suggests that nosocomial spread of tuberculosis can be decreased by means of previously established, less costly methods.     

Two-step tuberculin skin test in general hospital workers--comparison with nursing home workers

In 1998, the Japanese Society for Tuberculosis recommended two-step tuberculin skin test (TST) for medical workers. As a large majority of the Japanese were BCG vaccinated in their childhood, it is difficult to distinguish true infection from booster effect. In Japan, it is important to record individual baseline tuberculin reactivity by two-step TST. Two-step TST was performed on 126 general hospital workers and 47 nursing home workers, excluding those whose initial TST was strongly positive, according to the recommendation of the Japanese Society for Tuberculosis in 1998 (strongly positive TST in Japan is defined as the reaction with other intensive responses such as double skin erythema, bleb, lymphangitis, etc.). Diameter of erythema of TST among hospital workers v.s. nursing home workers were as follows. In the initial TST: 23.2 +/- 16.7 mm v.s. 14.2 +/- 10.3 mm (p < 0.001), in the second TST: 26.3 +/- 17.1 mm v.s. 16.7 +/- 9.9 mm (p < 0.02), baseline of TST: 32.0 +/- 18.3 mm v.s. 19.4 +/- 10.7 mm (p < 0.001). Booster effect of TST in hospital workers was +9.8 +/- 15.1 mm, while it was +4.8 +/- 7.8 mm (not significant) in nursing home workers. Among those 30 years and over, these differences were no found, except diameter of erythema in the initial TST. In our hospital with no beds for TB, in the past 10 years, tuberculosis has not been broken out among our hospital workers, while several patients with pulmonary tuberculosis have been diagnosed every year (6 patients in 1999). Thus, some hospital workers might be exposed to infection with tuberculosis from these patients. On the other hands, no tuberculosis patients had been diagnosed in the nursing home, and young nursing home workers very rarely exposed to infection with tuberculosis in their life, and they are similar to the general population. This study suggested that hospital workers were more frequently exposed to tuberculosis infection than other workers.     

Prevalence and predictors of tuberculin skin positivity in Hellenic Army recruits

Background  

Tuberculosis (TB) remains one of the leading causes of death among infectious diseases worldwide. Despite its low incidence rates in countries of Western Europe and North America, the resurgence of TB in Eastern Europe and the increased immigration from high-incidence countries imply that extreme vigilance is required in order to detect early, treat, and isolate all new cases. In this study, we analyzed the prevalence and predictors of tuberculin skin testing positivity in Hellenic Army recruits.     

The tuberculin skin test in relation to immunological in vitro reactions in BCG-vaccinated healthcare workers.

The aim was to study the tuberculin skin test in relation to immunological in vitro reactions in bacille Calmette-Guerin (BCG)-vaccinated healthcare workers. The present study was performed in Sweden, a country with a low incidence of tuberculosis, a high BCG vaccination efficacy and high tuberculin conversion rates. BCG-vaccinated healthcare workers (n=381) were tuberculin skin tested. From these, 11 subjects with negative tuberculin reactions (<6 mm) were matched for age and sex with 11 subjects with large positive reactions (> or = 15 mm). Lymphocyte transformation and the production of interferon-gamma (IFN-gamma) were analysed after stimulation in vitro of peripheral blood mononuclear cells with tuberculin purified protein derivative, heat-killed tubercle bacilli and a culture filtrate from tubercle bacilli. In the tuberculin-positive group the lymphocyte transformation response was 2-3 times larger, and IFN-gamma production was 7-10 times larger, than in the tuberculin-negative group (p<0.001). The present results suggest that a positive tuberculin skin test in bacille Calmette-Guerin-vaccinated subjects indicates a stronger immune response of the protective T-helper 1-type than does a negative test. In similar settings, the study supports the traditional practice of regarding the tuberculin skin test in bacille Calmette-Guerin-vaccinated subjects as an indicator of a protective immune response against tuberculosis.