Tuberculin Skin Test Conversion Rate Research Articles

High conversion of tuberculin skin tests during the first year of antiretroviral treatment among South African adults in primary care.

Anergy reduces the sensitivity of the tuberculin skin test (TST) to detect Mycobacterium tuberculosis infection in people living with HIV. Antiretroviral treatment (ART) can reverse TST anergy, but data is scarce. To estimate TST conversion rates and factors associated with TST conversion, TST was placed at ART initiation, and 6 and 12 months thereafter (if TST negative at prior assessment). Of 328 ART-eligible participants, 70% (231/328) had a valid TST result of whom 78% (180/231) were TST negative. At 6-month follow-up, 22% (24/109, 95% confidence interval [CI] 15%, 31%) of participants on ART, without incident tuberculosis (TB), and with a valid TST result converted to a positive TST. Of these 109 individuals, those with baseline CD4+ cell count >250 cells/μl were more likely to TST convert compared to those with baseline CD4+ cell count ≤250 cells/μl (odds ratio [OR] 3.54, 95% CI 1.29, 11.47). At 12 months post-ART initiation, an additional 12% (9/78, 95% CI 6, 20) of participants on ART, without incident TB and with a valid TST result experienced TST conversion. After 1 year on ART, TST conversion rate was 38 per 100 person-years (95% CI 26, 52), and lower in individuals with baseline CD4+ cell count ≤250 cells/μl (23/100 person-years, 95% CI 11, 41) compared to those with baseline CD4+ cell count >250 cells/μl (50/100 person-years, 95% CI 32, 73). TST conversion rate in the first year of ART is high, especially among people with CD4+ cell count >250 cells/μl. A TST-based eligibility strategy at ART initiation may underestimate eligibility for preventive therapy for tuberculosis.

Erratum to `Tuberculosis risk in the biologic era: tuberculin skin test conversion rates in children with rheumatologic diseases` [Turk J Pediatr 2021; 63: 978-985

This article is corrected. DOI: 10.24953/turkjped.2021.06.005.

Tuberculosis Exposure and Conversion Rates Can Guide Deimplementation of Annual Tuberculosis Screening

Background: The CDC recently updated recommendations on tuberculosis (TB) screening in healthcare facilities, suggesting the discontinuation of annual TB screening. However, hospitals may opt to continue based on their local TB epidemiology. We assessed TB infection control parameters in our facility to guide the implementation of the new CDC recommendations. Methods:We retrieved data for patients with an International Classification of Disease, Tenth Revision (ICD-10) code for TB treated at the University of Iowa Hospitals and Clinics during 2016–2019. We supplemented our search with microbiology data: culture or PCR for Mycobacterium tuberculosis. Based on manual chart review, we adjudicated each patient as active TB, latent TB, previously treated TB, unclear history, or no TB. We further labeled active TB cases based on their risk of transmission (pulmonary or extrapulmonary cases that underwent an aerosol generating procedure). We then calculated the number of exposure events associated with those patients and tuberculin skin test (TST) conversion rates among the exposed. Results: During 2016–2019, we identified 197 patients based on ICD-10 codes. In total, 10 additional patients were detected by microbiology data review. Of these 207 patients, 48 (23.2%) had active TB: lung, n = 24 (50%); lymph node, n = 9 (19%); bone or spine, n = 5 (10%); eye, n = 3 (6%); disseminated, n = 2 (4%); pleura, n = 2 (4%); skin abscess, n = 2 (4%); and meningitis, n = 1 (2%). Of the 24 pulmonary patients, 6 (25%) had either a positive smear or a cavity on imaging. In total, 159 patients were excluded: no TB, n = 22 (14%); latent TB, n = 27 (17%); old or treated TB, n = 93 (58%); and unclear history, n = 9 (6%). Of the 48 cases with active TB, 31 (65%) were deemed potentially infectious. Also, 10 cases (32%) led to the exposure of 204 healthcare workers (HCWs). Baseline and postexposure TST were available for 179 HCWs (88%); 72 (35%) followed up in the employee health clinic within the 8–12 weeks after exposure. Of 161 HCWs with a negative TST at baseline, no conversions occurred. Of 18 HCWs with positive TST at baseline, no HCW developed symptoms during the observation period. Conclusions: Nearly one-third of infectious TB cases led to HCW exposures in a low-incidence setting. However, no TST conversions or active TB infections were seen. Exposure and conversion rates are useful indicators of TB infection control in healthcare facilities and may help guide implementation of the new CDC TB control recommendations.Funding: NoneDisclosures: None

Conversion Rate of Tuberculin Skin Test among Medical Students in Songklanagarind Hospital

OBJECTIVE: Airborne and Tuberculosis (TB) control measures have been implemented in Songklanagarind hospital. The infection control unit of the hospital has provided a voluntary two-step tuberculin skin test (TST) for pre-clinical medical students and serial TST for clinical medical students. This study aimed to determine the incidence of negative outcome and booster phenomenon from two-step TST as well as the TST conversion rate from serial TST among medical students in the hospital. MATERIALS AND METHODS: Percentages of negative cases and boosting phenomenon were calculated from the two-step TST records. Conversion rates of each year were calculated from serial TST data. Then the TST conversion rates were predicted based on the Jointpoint model. RESULTS: Two-step TSTs performed from 2001 to 2016 showed 40 to 100% of negative cases and zero to 14% of boosting phenomenon among 2,271 medical students. Serial TSTs from 2002 to 2016 among 665 medical students showed 60 conversion cases. Conversion rates varied from zero to 13.6%. The decline of conversion rates after the year 2006 is demonstrated in 1-Joinpoint model with statistical significance (p = 0.0129). The model corresponded with the timeline data of airborne infection control measures which were mostly implemented after 2006. CONCLUSIONS: A decline in TST conversion rate was shown after 2006. This coincided with airborne infection control measures at the institute. Keywords: tuberculin skin test, conversion rate, medical student, Songklanagarind hospital Address Correspondence to author: Sarinpant Pongpant, MD. Occupational health unit, Department of family medicine and preventive medicine, Faculty of Medicine, Prince of Songkla University, Songkhla, 90110, Thailand. email: jibpongpant@gmail.com Received: May 25, 2018 Revision received: May 31, 2018 Accepted after revision: July 3, 2018 BKK Med J 2018;14(2): 17-21. DOI: 10.31524/bkkmedj.2018.09.004

Safety and Immunogenicity of Early Bacillus Calmette-Guérin Vaccination in Infants Who Are Preterm and/or Have Low Birth Weights

Bacillus Calmette-Guérin (BCG) vaccination is commonly delayed in infants who are preterm and have low birth weights (LBW) despite the association of early vaccination with better vaccination coverage and potentially nonspecific benefits for survival. To determine the safety, immunogenicity, and protective efficacy against tuberculosis (TB) of BCG vaccination given at or before 7 days after birth vs vaccination more than 7 days after birth among infants who are preterm and/or had LBW. Searches of Medline, Embase, and Global Health databases were conducted from inception until August 8, 2017. Clinical trials, cohort studies, and case-control studies that included infants who were preterm and/or had LBW and reported safety, mortality, immunogenicity, proxies of vaccine take, and/or efficacy against TB. Two authors independently extracted data and assessed the quality of the studies. Data extracted included demographics, covariates, sources of bias, and effect estimates. Meta-analysis was performed using a random-effects model. Safety, mortality, immunogenicity, or other proxies of vaccine take, such as tuberculin skin test (TST) conversion and efficacy against tuberculosis. Forty studies were included in a qualitative synthesis; infants who were preterm (born at 26-37 weeks' gestational age) and/or had LBW (0.69-2.5 kg at birth) were included. The BCG vaccine was administered at or before 7 days to 10 568 clinically stable infants who were preterm and/or had LBW; vaccination was administered to 4310 infants at varying times between 8 days and 12 months after birth. Twenty-one studies reporting safety found no cases of BCG-associated death or systemic disease in 8243 infants. Four studies reported no increase in all-cause mortality for infants who had LBW and who received early BCG vaccination compared with infants who had LBW with later vaccination or BCG-vaccinated infants of normal birth weight. Four studies reported lymphadenitis incidence; combined, these reported 0% to 2.9% incidence of vaccination within 7 days and 0% to 4.2% of vaccination after 7 days. Meta-analysis of 7 studies revealed no differences between early and delayed BCG vaccination for scar formation (n = 515; relative risk [RR], 1.01 [95% CI, 0.95-1.07]) or TST conversion (n = 397; RR, 0.97 [95% CI, 0.84-1.13]). Published data were insufficient to assess immunogenicity or protective efficacy against TB disease. Early BCG vaccination in healthy infants who are preterm and/or had LBW has a similar safety profile, reactogenicity, and TST conversion rate as delayed vaccination. Based on current evidence, early BCG vaccination in stable infants who are preterm and/or have LBW to optimize uptake is warranted.

Serial testing of healthcare workers for latent tuberculosis infection and long-term follow up for development of active tuberculosis.

BackgroundHealthcare workers (HCWs) are at high risk of tuberculosis (TB) infection due to occupational exposure. It is important to diagnose TB infections in HCWs to prevent nosocomial transmission, particularly among immunocompromised patients.ObjectiveThe aim of this study was to analyze the rate of tuberculin skin test (TST) conversion and to assess the incidence of active TB after the latent TB infection screenings in high-risk HCWs.MethodsThis retrospective cohort study involved 458 HCWs in TB-related departments between 2009 and 2013. All HCWs underwent a TST and a chest radiograph annually; an interferon-γ release assay (IGRA) was performed on the TST-converted subjects. TST-converted and IGRA-positive HCWs underwent treatment for latent TB infection.ResultsThe TST conversion rate was 30.3% from 2009 to 2011 in two years, 7.4% from 2011 to 2012, and 17.4% from 2012 to 2013. Eleven subjects out of 42 TST converters (26%) were IGRA-positive; two of them developed into active pulmonary TB during the follow-up period.ConclusionsThere was significant discordance between TST conversion and IGRA results in high-risk HCWs, and active TB developed only in TST-converted and IGRA-positive HCWs. Therefore, the combined use of TST and IGRA for periodic monitoring of TB infections in high-risk HCWs may be useful.

P531 Tuberculin skin test conversion rate in inflammatory bowel disease patients receiving anti-TNFα agents

Anti-TNFα therapy increases the risk of tuberculosis (TB) (re)-activation in inflammatory bowel disease (IBD) patients. Purified protein derivative tuberculin skin test (PPD-TST) is considered a pre-requisite at baseline. However, few data exist regarding the kinetics of this test during therapy. Therefore, our study investigated the conversion rate of PPD-TST in IBD patients under anti-TNFα treatment. Anti-TNFα treated IBD patients followed up in our centre with a baseline PPD-TST underwent a sequential one during therapy. Those with a positive PPD-TST either at baseline or during therapy (d > 10 mm in naïve and d > 5 mm in those exposed to immunomodulators [IMS]) received 300 mg isoniazid orally for 9 months. Sixty-eight IBD patients have been enrolled so far (males: 51.47%, Crohn’s disease: 82.35%). Median age at IBD diagnosis was 33.1 years [IQR: 20.3, range: 16.7–66.7]. Median duration of IBD was 7.7 months [IQR: 9.8, range: 1.4–32.7]. Nine patients (13.23%) had a positive PPD-TST at baseline. Fifty-eight patients have undergone a second PPD-TST (median time between the first and second PPD-TST: 27.10 months [IQR: 41.22, range: 6.3–190.1]). Nineteen patients were under combination therapy with an IMS at the second PPD-TST. In seven patients with a positive baseline PPD-TST, this remained positive (in five patients the diameter was decreased and in two increased) and in one it turned negative. Out of the remaining 50 patients with a negative baseline PPD-TST, 10 (20%) exhibited a positive second PPD TST; three of them were receiving infliximab for less than 3 years and seven of them adalimumab (three for less and four for more than 3 years). Only 3 of 10 were under combination therapy. No case of active tuberculosis has been detected in this cohort so far. All patients with a PPD-TST conversion received anti-tuberculous treatment. A positive PPD-TST followed by anti-TB treatment before the initiation of anti-TNFα in IBD patients was not associated with an increased rate of TB infection during therapy. In one-fifth of the patients with a negative baseline PPD-TST the test exhibited conversion but without any undesirable consequence if so treated.

LATENT TUBERCULOSIS AMONG PROFESSIONALS FROM A REFERRAL HOSPITAL IN ONCOLOGY

Introduction: Tuberculosis (TB) is an ancient contagious disease, and continues to be the leading cause of morbidity and mortality among infectious contagious diseases. It can be considered an occupational infectious disease when it happens in health professionals. These professionals are directly exposed to TB and are considered to be a high risk population for latent tuberculosis infection (LTBI) and active TB. The primary aim of this study was to estimate the prevalence of LTBI among the clinical and administrative staff of an oncology referral hospital in Rio Grande do Sul. The secondary aim of this study was evaluate tuberculin skin test (TST) conversion rate and the risk factors for TST positivity in this population. Methods : A cross-sectional study was carried out in a retrospective cohort with data collected in March 2013 and March 2014. Data of professionals from different hospital units were included. Those with induration ≥ 10 mm were considered as reactors, and conversion rate was assessed by an increase ≥ 10 mm in induration in the second TST compared with the first one. Results: Among the 225 professionals evaluated in 2013, 135 (60%) were reactors and 90 (40%) were non-reactors. The mean age was 32.9 (± 9.55), 176 (78.22%) were female, and most of the reactors worked in the hospital for 4 years or less. Non-reactors in 2013 were recommended to repeat the test in 2014, and the conversion rate was 9.37%. There was no significant difference in prevalence among the different professional categories, and the assessed risk factors were not associated with ILTB. Conclusions: The prevalence of LTBI in the study population was high, reinforcing the need to implement effective control measures to prevent LTBI in the hospital where the study was conducted. Keywords: Latent tuberculosis; occupational risk; tuberculin test; vulnerable populations

Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines.

Transmission is driving the global tuberculosis epidemic, especially in congregate settings. Worldwide, natural ventilation is the most common means of air disinfection, but it is inherently unreliable and of limited use in cold climates. Upper room germicidal ultraviolet (UV) air disinfection with air mixing has been shown to be highly effective, but improved evidence-based dosing guidelines are needed. To test the efficacy of upper room germicidal air disinfection with air mixing to reduce tuberculosis transmission under real hospital conditions, and to define the application parameters responsible as a basis for proposed new dosing guidelines. Over an exposure period of 7 months, 90 guinea pigs breathed only untreated exhaust ward air, and another 90 guinea pigs breathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection was turned on throughout the ward. The tuberculin skin test conversion rates (>6 mm) of the two chambers were compared. The hazard ratio for guinea pigs in the control chamber converting their skin test to positive was 4.9 (95% confidence interval, 2.8-8.6), with an efficacy of approximately 80%. Upper room germicidal UV air disinfection with air mixing was highly effective in reducing tuberculosis transmission under hospital conditions. These data support using either a total fixture output (rather than electrical or UV lamp wattage) of 15-20 mW/m(3) total room volume, or an average whole-room UV irradiance (fluence rate) of 5-7 μW/cm(2), calculated by a lighting computer-assisted design program modified for UV use.

Incidence of occupational latent tuberculosis infection in South African healthcare workers.

The test-specific incidence of latent tuberculosis infection (LTBI) in healthcare workers from sub-Saharan Africa is unknown. 505 healthcare workers from South Africa were screened at baseline, and after 12 months, with a questionnaire, the tuberculin skin test (TST), and two T-cell assays (T-SPOT.TB and QuantiFERON-TB Gold-In-Tube). Test-specific conversion rates were calculated. The prevalence of presumed LTBI at baseline was 84, 69 and 62% using the TST, QuantiFERON-TB Gold-In-Tube and T-SPOT.TB, respectively. The annual test-specific conversion rate, depending on the cut-off point used, was as follows: TST 38%; QuantiFERON-TB Gold-In-Tube 13-22%; and T-SPOT.TB 18-22%. Annual reversion rates were 4, 7 and 16%, respectively. The annual TST conversion rate was significantly higher than that derived from published local community-based data (IRR 3.53, 95% CI 1.81-6.88). Factors associated with conversion (any test) included healthcare sector of employment, counselling of tuberculosis patients, and a baseline positive TST (for T-SPOT.TB). The annual rate of tuberculosis infection in South African healthcare workers was very high, irrespective of the testing method used, and may be explained by occupational exposure, as the rate was considerably higher than non-healthcare workers from the same community. Collectively, these data support the need for implementation of tuberculosis-specific infection control measures in Africa.

Challenges with QuantiFERON-TB Gold Assay for Large-Scale, Routine Screening of U.S. Healthcare Workers

North American occupational health programs that switched from the tuberculin skin test (TST) to IFN-γ release assays for latent tuberculosis screening are reporting challenges with interpretation of serial testing results in healthcare workers (HCWs). However, limited data exist on the reproducibility of serial IFN-γ release assay results in low-risk HCWs. To evaluate the short-term reproducibility of QuantiFERON-TB Gold In-Tube (QFT) in a large cohort of HCWs and to define a QFT cutoff yielding a conversion rate equivalent to historical TST rates. We retrospectively evaluated the QFT results from HCWs with two or more QFT tests performed between June 2008 and July 2010 at an academic institution. Outcome measures were proportions of reproducibility, quantitative results, and conversion rates with alternate QFT cutoffs. A total of 9,153 HCWs with two or more QFT tests were included in the analysis. Of 8,227 individuals with a negative result, 4.4% (n = 361) converted their QFT result over 2 years. A total of 261 (72.3%) of the HCWs with conversions underwent repeat short-term testing after the first positive result with 64.8% reverting (n = 169). An IFN-γ cutoff of 5.3 IU/ml or higher (manufacturer's cutoff is ≥0.35 IU/ml) yielded a conversion rate of 0.4%, equal to our institution's historical TST conversion rate. The manufacturer's definition of QFT conversion results in an inflated conversion rate that is incompatible with our low-risk setting. A significantly higher QFT cutoff value is needed to match the historical TST conversion rate. Nonreproducible conversions in most converters suggested false-positive results.

Tuberculin skin test conversion rate among short-term health care workers returning from Gaborone, Botswana

Our objective was to determine tuberculin skin test conversion rate of health care workers traveling to Botswana. The rate of tuberculin skin test conversion was 4.2% for the entire group studied or 6.87 per 1000 person weeks (95% CI, 1.87-17.60). International travel by health care workers traveling from low incidence countries to areas of the world where tuberculosis is highly endemic places the health care worker at an increased risk of acquiring tuberculosis. To determine the tuberculin skin test conversion rate of health care workers living in the United States with previously negative tuberculin skin test results working for less than 1 year in a hospital in Botswana where tuberculosis is highly endemic. We performed a cross-sectional survey among health care workers affiliated with the University of Pennsylvania School of Medicine who participated in patient care in Botswana between July 1st 2004 and June 30th 2009. We recruited health care workers after returning from Botswana who had a documented negative tuberculin skin test in the year prior to travel, who spent at least 2 weeks but not more than 1 year and who had a documented tuberculin skin test 2-3 months post travel. The main study outcome was a positive tuberculin skin test 6-12 weeks after returning from Botswana, defined by an area of at least 10mm induration 48-72h after placement of the tuberculin skin test. 95 Subjects participated in the study and there were 4 tuberculin skin test conversions. The rate of tuberculin skin test conversion in our study population was 4.2% for the entire group studied or 6.87 per 1000 person weeks (95% CI, 1.87-17.60). The tuberculin skin test conversion rate was higher than the reported conversion rates for those not working in a health care setting.

Prevalence and Incidence of Latent Tuberculosis Infection in Georgian Healthcare Workers

BackgroundTuberculosis is a major occupational hazard in low and middle-income countries. Limited data exist on serial testing of healthcare workers (HCWs) with interferon-γ release assays (IGRAs) for latent tuberculosis infection (LTBI), especially in low and middle-income countries. We sought to evaluate the rates of and risk factors for LTBI prevalence and LTBI test conversion among HCWs using the tuberculin skin test (TST) and QuantiFERON-TB Gold In-tube assay (QFT-GIT).MethodsA prospective longitudinal study was conducted among HCWs in the country of Georgia. Subjects completed a questionnaire, and TST and QFT-GIT tests were performed. LTBI testing was repeated 6-26 months after baseline testing.ResultsAmong 319 HCWs enrolled, 89% reported prior BCG vaccination, and 60% worked in TB healthcare facilities (HCFs). HCWs from TB HCFs had higher prevalence of positive QFT-GIT and TST than those from non-TB HCFs: 107/194 (55%) vs. 30/125 (31%) QFT-GIT positive (p<0.0001) and 128/189 (69%) vs. 64/119 (54%) TST positive (p = 0.01). There was fair agreement between TST and QFT-GIT (kappa = 0.42, 95% CI 0.31–0.52). In multivariate analysis, frequent contact with TB patients was associated with increased risk of positive QFT-GIT (aOR 3.04, 95% CI 1.79–5.14) but not positive TST. Increasing age was associated with increased risk of positive QFT-GIT (aOR 1.05, 95% CI 1.01–1.09) and TST (aOR 1.05, 95% CI 1.01–1.10). High rates of HCW conversion were seen: the QFT-GIT conversion rate was 22.8/100 person-years, and TST conversion rate was 17.1/100 person-years. In multivariate analysis, female HCWs had decreased risk of TST conversion (aOR 0.05, 95% CI 0.01–0.43), and older HCWs had increased risk of QFT-GIT conversion (aOR 1.07 per year, 95% CI 1.01–1.13).ConclusionLTBI prevalence and LTBI test conversion rates were high among Georgian HCWs, especially among those working at TB HCFs. These data highlight the need for increased implementation of TB infection control measures.

Occupational Infections among Health Care Workers in a Secondary Care Hospital Saudi Arabia

Introduction: Healthcare workers (HCWs) are frequently exposed to various infectious agents while performing their duties and many accidental exposures to blood borne and air borne pathogens are preventable if health care workers comply with appropriate precautions. Objectives: Assessment of some occupational exposure among health care workers in a secondary care hospital- Najran province- Saudi Arabia during the period (2009-2012). Subjects and methods: Retrospective review of health care workers’ (HCWs) records from staff health clinic to determine the distribution of occupational infections among different job categories which was confirmed by clinical manifestations, laboratory investigations and reports of needle stick incidents to which HCWs were exposed during period of data collection. Results: The most common occupational infection among healthcare workers was chicken pox. There was low Tuberculin skin test (TST) conversion rate among different professional categories and nurses were the most affected occupational category during the study period as regard exposure to sharp injuries and air borne infections. Conclusions: Management policy and procedures should be directed and implemented to minimize and prevent occupational infections with emphasis on nurses as being the highly affected risk group.

Risk factors for tuberculin skin test conversion among HIV-infected patients in New York City

We assessed the incidence of and risk factors for tuberculin skin test (TST) conversion among HIV-infected adults at a New York City clinic. All adult HIV-infected patients were eligible for inclusion if they had a negative baseline TST result and at least one subsequent documented TST test result. A total of 414 HIV-infected patients had a negative baseline TST result; 288 (69.6%) were male. Among 348 patients who had a place of birth documented, 50% were born outside of mainland USA. Twenty-two (5.3%) of 414 patients had documented TST conversions, giving a crude incidence rate of 1.77 per 100 person-years. Being a foreign-born Asian individual (p=0.02), having lived in a shelter (p=0.004), and having an increase in CD4 cell count (p=0.02) while under care were independent risk factors for TST conversion. We found a high TST conversion rate among HIV-infected patients attending an urban clinic. Annual TST testing is particularly important for patients who are foreign-born from high-endemic countries, those with a history of homelessness, and those with an increase in CD4 cell count since the baseline negative TST test.

Housekeeping health care workers have the highest risk for tuberculin skin test conversion

Not all health care workers (HCWs) are at the same risk for tuberculin skin test (TST) conversion, indicating latent tuberculosis (TB) infection. To identify risk factors for TST conversion among HCWs. A retrospective cohort study conducted at a tertiary university medical centre included every HCW who had had a negative two-step TST at work entry and at least one consecutive TST in the period 2005-2009 (mean follow-up period 55 months). Binomic logistic regression analysis was used to identify risk factors for TST conversion. Potential risk factors such as age, health care profession, patient exposure profile, workplace division and history of bacille Calmette-Guérin vaccination were entered in the model. A total of 450 subjects met the inclusion criteria, of whom 93 had TST conversion. The highest annual rates of TST conversion occurred in workers who worked as housekeeping staff (6.9%). Older age, a work environment with high patient turnover and employment in maintenance departments were significant risk factors (adjusted odds ratios 2.05, 5.2 and 8.4 respectively). Housekeeping staff, older age workers and health care professionals working in an environment of high patient turnover are at increased risk for latent TB infection.

Housing Insecurity and Lack of Public Assistance are Risk Factors for Tuberculin Skin Test Conversion Among Persons Who Use Illicit Drugs in New York City

Persons who use illicit drugs are at increased risk of new tuberculosis (TB) infection. We conducted a prospective cohort study to assess rates and risk factors for tuberculin skin test (TST) conversion among persons with a history of illicit drug use, who were enrolled in a methadone program and had a negative baseline 2-step TST (eligible participants). TST and standardized interviews were administered to 401 eligible participants from 1995 through 1999, every 6 months for a 2-year follow-up time. Analyses were conducted in 2006. A total of 1,447 repeat TSTs were performed during 843 person-years of follow-up (median: 2.0 years). The TST conversion rate was 3.7 per 100 person-years. In multivariate analysis, participants who converted were more likely to report ever having been homeless (HR, 2.4; 95% CI, 1.2-5.0) or ever having lived in a homeless shelter (HR, 2.4; 95% CI, 1.2-4.9) at the baseline interview, and less likely to have reported receiving public assistance since the last study visit (RR, 0.15; 95% CI, 0.07-0.32). This is the first study utilizing 2-step TST at baseline to measure the incidence of TST conversion among persons who use illicit drugs. Controlling for homelessness, persons with a lack of current public assistance was identified as a risk factor for TST conversion. These individuals may most benefit from annual tuberculin skin testing.

Protecting health care workers from tuberculosis: A 10-year experience

Cook County Hospital (CCH) is an inner-city, large public hospital. Twenty-five percent of Chicago's tuberculosis (TB) cases are diagnosed at CCH. We wanted to review and analyze interventions implemented over a 10-year period at CCH to prevent TB infection in health care workers. We performed a retrospective review of interventions to prevent health care-associated tuberculosis. We collated and analyzed tuberculin skin test conversions in our employees for the same time period. From 1990 to 2002, we cared for over 1800 in-patients with tuberculosis. During 1992-1997, multiple interventions to eliminate health care-associated spread of tuberculosis were implemented. Tuberculin skin test conversions in our employees decreased markedly from January 1994 through December 2002. Two drops in tuberculin skin test conversion rates occurred: one after introduction of basic administrative and engineering controls and a second after we experienced a decrease in missed TB cases and the introduction of N-95 personal respirators with 1-time qualitative fit testing. Our annual health care worker skin test conversion rate fell significantly when our primary interventions were relatively simple administrative and engineering controls. Educating health care workers to promptly recognize patients with TB and placing exhaust fans to create negative-pressure respiratory isolation rooms were probably our 2 most potent infection control measures.

Differences in Tuberculin Reactivity as Determined in a Veterans Administration Employee Health Screening Program

In response to a difference in pricing, the San Diego Veterans Administration Medical Center changed its tuberculin preparation from Tubersol to Aplisol in the fall of 2006. Following the change, an increased number of employee skin test conversions was noted. Employee tuberculin skin test converters from 2006 were screened with the QuantiFERON Gold (QFT-G) gamma interferon release assay. Those employees who tested negative by QFT-G were asked to repeat their skin test with both Tubersol and Aplisol tuberculin preparations. Of the new purified protein derivative converters, 12 of 14 returned for repeat testing with QFT-G, and the assay was negative for 83% (10/12), positive for 8% (1/12), and indeterminate for 8% (1/12) of the individuals. Nine of the individuals who were QFT-G negative agreed to repeat skin testing with both tuberculin preparations, and 7/8 (87.5%) demonstrated reactivity with the Aplisol preparation, while 0/8 (0%) reacted to the Tubersol preparation. A change from Tubersol to Aplisol resulted in elevated tuberculin skin test conversion rates that may be due to false-positive reactions. The differences in skin test reactivity between preparations support CDC guidelines that recommend that institutions should not change tuberculin preparations, as doing so may falsely increase the number of positive reactions.

Effectiveness of the combination of a whole‐blood interferon‐gamma assay and the tuberculin skin test in detecting latent tuberculosis infection in rheumatoid arthritis patients receiving adalimumab therapy

To investigate QuantiFERON-tuberculosis Gold (QFT-G) assay and tuberculin skin test (TST) for latent tuberculosis (TB) infection (LTBI) in patients with rheumatoid arthritis (RA) treated with adalimumab. We prospectively followed up 43 RA patients who received adalimumab therapy and underwent serial TSTs and QFT-G assays. TST was performed using Mantoux method and QFT-G assay was examined by measuring interferon-gamma levels in whole blood samples that were incubated with early secretary antigenic target-6 and culture filtrate protein 10. Before starting adalimumab therapy, 8 RA patients (18.6%) had positive and 35 (81.4%) had negative TST results. All 8 RA patients with positive TST results were diagnosed as LTBI and received isoniazid prophylaxis (INHP) 1 month before starting adalimumab therapy. None of these 8 RA patients developed active TB 2 years after completing INHP. A high rate (10 [37.0%] patients) of TST conversion was observed among 27 patients who had completed 12-month adalimumab therapy. Of these 10 patients with TST conversion, 2 patients had positive QFT-G results and 1 developed active TB disease. Among 17 RA patients who did not have TST conversion after 12-month adalimumab therapy, 1 patient who had a positive QFT-G result developed active TB disease. Of all 43 RA patients who received adalimumab therapy, 4 (9.3%) developed active TB after starting adalimumab therapy. The application of TST for detecting LTBI is limited in RA patients by the frequent presence of anergy. Combined QFT-G assay and TST can aid in detecting LTBI in RA patients receiving adalimumab therapy.