Tuberculin Skin Test Positivity Rate Research Articles

Tuberculin skin testing and QuantiFERON™-TB Gold Plus positivity among household contacts in Vietnam.

TB infection (TBI) is diagnosed using the technique-dependent tuberculin skin test (TST) or costly, more accurate interferon-gamma release assays. The TST (⩾10 mm) threshold was indicated by previous research among household contacts in Vietnam, but routine implementation with a different tuberculin reagent showed unexpectedly low TST positivity. TST (⩾5 mm and ⩾10 mm) results were compared to QuantiFERON™-TB Gold Plus (QFT) results in household contacts during community campaigns in 2020 and 2021. This was a cross-sectional multi-center implementation study. Among 1,330 household contacts in 2020, we found a TBI prevalence of 38.6% (QFT), similar to TST ⩾5 mm (37.4%) and higher than TST ⩾10 mm (13.1%). QFT+/TST+ was higher for TST ⩾5 mm (20.7%) than TST ⩾10 mm (9.4%). QFT was not discordant with TST ⩾5 mm (McNemar's test = 0.6, P = 0.5) but was discordant with TST ⩾10 mm (McNemar's test = 263.9, P < 0.01). Older age and Southern region increased odds for positive TST ⩾5 mm and QFT with weaker associations for TST ⩾10 mm. Agreement and discordance were similar in 2021 for 1,158 household contacts. Tuberculin reagents affect TST positivity rates. High TB burden countries should monitor reliability of TBI diagnosis, including tuberculin potency, cold chain, and TST technique to optimize eligibility for TB preventive treatment.

Latent tuberculosis infection in liver transplant patients: a review.

Latent tuberculosis infection in liver transplant patients: a review.

Selection of the cutoff value of the tuberculin skin test for diagnosing students who need preventive treatment: A school-based cross-sectional study

ObjectiveTuberculosis outbreaks in schools are common in China. This study aimed to introduce and evaluate a new screening process to help control outbreaks.MethodsScreening information of students in three schools with tuberculosis outbreaks was collected. QuantiFERON-TB gold in-tube (QFT) results were used as the reference standard to determine the cutoff value of the tuberculin skin test (TST) for diagnosing students who need to have preventive medication.ResultsA total of 1,232 students and teachers from three different schools that all had more than three student patients with tuberculosis were included in this study. In total, 308 (25.0%) students had an induration diameter ≥10 mm; among students in a class different from the index case, the infection rate was 24.4% (264/1,084), which was lower than the rate among students in the same class (29.7%) (P = 0.157). Students in the same class as the index tuberculosis case had a much higher QFT positivity compared to those in a different class (58.1% vs. 7.7%, P < 0.0001). Diagnostic agreement between TST ≥10 mm and QFT was 36.6%. The diagnostic value reached the highest when the induration diameter of TST was ≥9 mm, with a sensitivity and specificity of 94.1% (95% CI: 89.4%–97.1%) and 27.6% (95% CI: 24.9%–30.4%), respectively. The area under the curve (AUC) was 0.664 (95% CI: 0.637–0.690, P < 0.0001).ConclusionIn tuberculosis outbreaks in schools, if there are three or more cases of students with tuberculosis in a class or if the moderate or strong TST positivity rate is much higher than the normal range in the region, attention should be paid to those with moderately positive TST results. Interferon-gamma release assays (IGRAs) are recommended to be conducted following TST on the day of reading the results, especially among students sharing the same class with the index case. In resource-poor areas lacking IGRAs, the induration diameter of TST can be appropriately reduced from 15 to 9 mm to enhance the sensitivity of TST.

Screening for TB infection: the operator´s impact.

BACKGROUND: Accurate diagnosis of TB infection (TBI) is challenging due to the lack of a gold standard. Tuberculin skin test (TST) and interferon-gamma release assay (IGRA) are currently useful in TBI diagnosis, but both have several limitations. This study aims to evaluate inter-operator variability in TST measurements and determine its impact on TBI diagnosis and treatment.METHODS: This was a retrospective analysis of patients screened for TBI using at least TST at a public outpatient clinic specialised in TB from January 2019 to August 2021. TST readings performed by five experienced nurses were compared.RESULTS: A total of 671 screenings were analysed. TST positivity rate (P < 0.001) and mean TST measurements obtained by our nurses were significantly different (P < 0.001). Concordance of TST and IGRA results was of 83.4% in the overall population (κ = 0.479). However, TST/IGRA agreement was significantly different among nurses (P = 0.003).CONCLUSION: Our analysis of TST measurements by experienced nurses shows significant differences in TST positivity rate, mean measured values and overall concordance with IGRA. This led to significant different outcomes in TBI diagnosis and subsequent treatment. TST measurement differences could potentially be more pronounced if we considered untrained operators or those with occasional reading experience.

Tuberculin skin test before biologic and targeted therapies: does the same rule apply for all?

This study aimed to compare Tuberculin Skin Test (TST) and QuantiFERON®-TB Gold In-Tube (QFT-GIT) test in rheumatoid arthritis (RA) and spondyloarthritis (SpA) patients scheduled for biological and targeted synthetic disease modifying anti-rheumatic drugs (DMARDs) in a Bacillus Calmette-Guérin-vaccinated population. Adult RA (n = 206) and SpA (n = 392) patients from the TReasure database who had both TST and QFT-GIT prior to initiation of biological and targeted synthetic DMARDs were included in the study. Demographic and disease characteristics along with pre-biologic DMARD and steroid use were recorded. The distribution of TST and performance with respect to QFT-GIT were compared between RA and SpA groups. Pre-biologic conventional DMARD and steroid use was higher in the RA group. TST positivity rates were 44.2% in RA and 69.1% in SpA for a 5mm cutoff (p < 0.001). Only 8.9% and 15% of the patients with RA and SpA, respectively, tested positive by QFT-GIT. The two tests poorly agreed in both groups at a TST cutoff of 5mm and increasing the TST cutoff only slightly increased the agreement. Among age, sex, education and smoking status, pre-biologic steroid and conventional DMARD use, disease group, and QFT-GIT positivity, which were associated with a 5mm or higher TST, only disease group (SpA) and QFT-GIT positivity remained significant in multiple logistic regression. TST positivity was more pronounced in SpA compared to that in RA and this was not explainable by pre-biologic DMARD and steroid use. The agreement of TST with QFT-GIT was poor in both groups. Using a 5mm TST cutoff for both diseases could result in overestimating LTBI in SpA.

Is the course of COVID-19 associated with tuberculin skin test diameter? A retrospective study.

The pathogenesis of coronavirus disease 2019 (COVID‐19) is still not fully understood. As severe acute respiratory syndrome coronavirus 2 (SARS‐COV‐2) has a similar pathogenetic pathway to Mycobacterium tuberculosis, it has been reported that there may be a relationship between Bacille Calmette–Guérin (BCG) vaccination rate and COVID‐19 severity. This study investigated the relationship between tuberculin skin test (TST) induration diameter and the clinical course of COVID‐19. Of 1963 adult patients who underwent TST, 76 patients with SARS‐COV‐2 infection confirmed by RT‐PCR analysis of respiratory tract samples were included in the study. Relationships between COVID‐19 clinical severity and TST positivity, induration size, and other clinical parameters were analyzed. Of the 76 patients, TST results were negative for 53 patients (69.7%) and positive for 23 patients (30.3%). COVID‐19 severity was mild in 47 patients (61.8%), moderate in 22 patients (28.9%), and severe in seven patients (9.3%). All TST‐positive patients had mild disease. Patients with mild disease had a significantly higher TST positivity rate (p < 0.001) and larger induration diameter (p < 0.001). The area under the receiver operating characteristic (ROC) curve of TST induration size for the differentiation of mild with moderate and severe disease was 0.768 (p < 0.001). The maximum Youden J index value was 0.522 at an induration diameter of 6.5 mm, which had a sensitivity of 66.0% and specificity of 86.2%. COVID‐19 patients with positive TST showed a significantly higher rate of mild disease than those with negative TST. TST positivity is favorably associated with the course of COVID‐19.

Prevalence of and risk factors associated with latent tuberculosis infection in a Latin American region

Tuberculosis (TB) represents a health problem in Colombia, and its control is focused on the search for contacts and treatment of TB cases underscoring the role of latent tuberculosis infection (LTBI) as a reservoir of Mycobacterium tuberculosis. The burden of LTBI in Colombia is unknown. We aimed to estimate the prevalence of LTBI and identify the associated risk factors. In this cross-sectional study, we recruited participants from four health care centers in Cali, Colombia. The participants were eligible if they were aged between 14 and 70 years, and all participants answered a survey evaluating their medical history and sociodemographic and lifestyle factors. LTBI status was based on tuberculin skin test (TST) positivity using two thresholds: ≥10 mm (TST-10) and ≥15 mm (TST-15). The magnitude of the associations between independent factors and dependent outcomes (LTBI status and TST induration) were evaluated by logistic regression and generalized linear models, respectively. A total of 589 individuals were included with TST positivity rates of 25.3% (TST-10) and 13.2% (TST-15). Logistic regression showed that being between age 40 and 69 years (OR = 7.28, 95% CI [1.62–32.7]), being male (OR = 1.71, 95% CI [1.04–2.84]), being employed (OR = 1.56, 95% CI [1.02–2.38]), and having a low intake of alcohol (OR = 2.40, 95% CI [1.13–5.11]) were risk factors for TST positivity, while living in the north zone (OR = 0.32, 95% CI [0.18–0.55]), living in the suburb zone (OR = 0.28, 95% CI [0.15–0.52]) and having a secondary education (OR = 0.49 95% CI [0.29–0.83]) lowered the risk of TST positivity. The generalized linear model showed that the previous predictors, as well as a low body mass index, had an effect on TST reaction size. The LTBI prevalence found in the population was moderate, reflecting the continuous transmission of M. tuberculosis. Social factors seem to play a decisive role in the risk of LTBI. Employed males, who are over 40 years of age, are overweight, have a lower level of education and have a low intake of alcohol (50–100 mL, once/week) should be a priority group for prophylactic treatment as a strategy for TB control in this city.

High rates of tuberculin skin test positivity due to methotrexate therapy: False positive results?

The tuberculin skin test (TST) and interferon ? release assays (IGRAs) are commonly used for latent tuberculosis infection (LTBI) screening. Unexpectedly high TST positivity rates have been reported in patients with rheumatic diseases, and methotrexate is frequently used in this population. We hypothesized that methotrexate use could be associated with false-positive TST results. To investigate whether treatment with methotrexate and other factors are associated with false-positive TST results in patients with rheumatic diseases. Prospective single-center study conducted between April 2013 and March 2016. Adult patients with rheumatic diseases were evaluated with a TST and two IGRAs for LTBI screening. We compared TST and IGRA results in patients treated and not treated with methotrexate and analyzed for factors associated with positive TST results. Our data suggest false-positive TST results associated with methotrexate therapy. Thus, we recommend against using the TST for LTBI screening in patients receiving methotrexate and the preferential use of IGRAs in such patients. We studied 393 patients with rheumatic diseases, including ankylosing spondylitis (ASP, n = 90), rheumatoid arthritis (RA; n = 120), psoriatic arthritis (PA, n = 126), and other disorders (n = 57). The rate of TST positivity varied across the groups: ASP 22.2%, RA 25%, PA 35.7%, and other disorders (22.8%). Positivity rates were lower with IGRAs. Methotrexate use was associated with a statistically significant two-fold increase in the risk of a positive TST and a dose– response relationship was observed. We found no statistically significant associations between methotrexate use and IGRA test positivity.

Tuberculin Skin Test and Quantiferon in BCG Vaccinated, Immunosuppressed Patients with Moderate-to-Severe Inflammatory Bowel Disease.

There are few data available on the effect of immunomodulator/biological therapy on the accuracy of the tuberculin skin test (TST) and interferon-gamma release assay (IGRA) in BCG-vaccinated immunosuppressed patients with inflammatory bowel disease (IBD). Our aim was to define the accuracy, predictors and agreement of TST and IGRA in a BCG-vaccinated immunosuppressed referral IBD cohort. 166 consecutive moderate-to-severe IBD patients (122 Crohn's disease, CD and 44 ulcerative colitis, UC) were enrolled in a prospective study from three centers. Patients were treated with immunosuppressives and/or biologicals. IGRA and TST were performed on the same day. Both in- and outpatient records were collected and comprehensively reviewed. TST positivity rate was 23.5%, 21.1%,14.5% and 13.9% when cut-off values of 5, 10, 15 and 20mm were used. IGRA positivity rate was 8.4% with indeterminate result in 0.6%. Chest X-ray was suggestive of latent tuberculosis in 2 patients. Correlation between TST and IGRA was moderate (kappa: 0.39-0.41, p<0.001). In addition, a cut-off of 14 and 17mm for TST was defined to identify IGRA positivity in a ROC analysis (AUC: 0.76, p=0.03). TST and/or IGRA positivity was not influenced by medical therapy or disease phenotype. Importantly, smoking was identified as a risk factor for TST but not IGRA positivity (OR: 2.70-5.02, p<0.01, for TSTcut-offs=5-20mm). TST and IGRA tests are partly complimentary methods, and additional testing by TST (with a cut-off of >15mm) should be considered to identify patients at risk for latent TB. Accuracy is satisfactory in BCG-vaccinated, immunosuppressed IBD patients. Smoking is a risk factor for TST positivity.

The effect of topical calcipotriol or zinc on tuberculin skin tests in hospitalised South African children

The tuberculin skin test (TST) is used to help diagnose tuberculosis (TB) in acutely ill hospitalised children. OBJECTIVE To investigate the potential augmentative effect of topical calcipotriol (a vitamin D analogue) or zinc on TST induration. Three TSTs were performed among 64 hospitalised children; each site was covered with topical aqueous cream (control), calcipotriol or zinc and assessed 24 and 48 h later by investigators blinded to all topical applications. TSTs were reactive in 15 (23.4%) children, of whom 13 (20.3%) were TST-positive. Topical calcipotriol and zinc induced TST positivity in two children with reactive but negative control TSTs. These treatments, however, did not significantly increase TST positivity rates. In children with reactive TSTs, the median 48 h induration diameter was not significantly different between the control, calcipotriol- or zinc-treated groups, which were respectively 12.0 (25%-75% IQR 5.0 - 18.0), 14.0 (25%-75% IQR 10.0 - 15.0) and 12.0 (25%-75% IQR 8.0 - 15.0) mm. Topical treatments did not induce TST reactivity or TST positivity in children with culture-confirmed TB disease (n = 4), human immunodeficiency virus infection (n= 18) or kwashiorkor (n = 9). Topical calcipotriol or zinc does not induce TST reactivity or significantly increase TST positivity rates in acutely ill hospitalised children. However, further studies are required to assess the effects of topical treatments on TST positivity in severely malnourished children.

Screening for Latent Tuberculosis Infection in Patients with Chronic Inflammatory Arthritis: Discrepancies Between Tuberculin Skin Test and Interferon-γ Release Assay Results

Screening for latent tuberculosis infection (LTBI) is mandatory before initiating biologics in patients with chronic inflammatory arthritis (CIA). However, few studies have evaluated the discrepancies between the results of tuberculin skin test (TST) and interferon-γ release assays (IGRA) in these patients. The purpose of our study was to investigate factors associated with TST and IGRA results in a large cohort of patients with CIA before the introduction of biologics. A total of 563 consecutive patients with CIA (293 rheumatoid arthritis, 270 spondyloarthritis) and eligible for biologics were prospectively enrolled. Demographic, clinical, and biological data were recorded. Risk factors for LTBI were assessed. All patients underwent a TST, a chest radiograph, and an IGRA test (T-SPOT.TB). Agreement between the 2 tests was low (κ = 0.16). The bacillus Calmette-Guerin (BCG) status was significantly associated with discordance between the 2 tests (p = 0.004). The TST positivity rate was 34.8%. Factors associated with a negative TST were female sex (p = 0.02) and immunosuppressive treatment (p = 0.003). The only LTBI risk factor associated with TST positivity was an abnormal chest radiograph (p = 0.02). T-SPOT.TB was positive in 21.7% of patients and indeterminate in 15.6%. Previous active TB and chest radiograph abnormalities were associated with IGRA positivity (p = 0.008 and p = 3.9 × 10(-5), respectively). The BCG vaccination was associated with negative IGRA (p = 3 × 10(-4)). Indeterminate IGRA results were associated with age, C-reactive protein, and immunosuppressive treatment (p = 0.005, 0.007, and 0.004, respectively). Our data support the combined use of T-SPOT.TB and TST in patients with CIA before biologics introduction. However, despite these good diagnostic values, indeterminate results may complicate the use of IGRA.

Evaluation of Tuberculin Skin Test Results among Students of the University of Medical Sciences and Technology, Sudan

Introduction: Tuberculosis is an endemic infectious disease in Sudan and other developing countries. Healthcare workers, including students, are at a great risk of exposure and possible infection. This study is conducted to determine the pattern and prevalence of positive tuberculin skin test (TST) among students of the University of Medical Sciences and Technology during distinct periods of their training, and to study the influencing factors for positive results. Design and Setting: A cross-sectional study conducted among 100 students in the period between October 2010 to March 2011 using questionnaires, and administration of the Tuberculin Skin Test (TST) by a licensed professional. Students were divided into two groups, high risk group (medical students), and low risk group (non-medical students) according to their level of exposure. Demographics, BCG vaccination, potential exposure to TB patients and symptomatology were obtained and analyzed. Results: The overall prevalence of positive TST was 19%, 2% were strongly positive, 17% being moderately positive. The high risk group exhibited a significantly higher rate of positive TST (26%). Positive TST was found to correlate significantly with contact with TB patients (P 0.08). No significant correlation was found between positive TST and gender (P 0.834), country of residence (P 0.242), vaccination (P 0.094), presence of BCG scar (P 0.793), drinking unpasteurized milk (p 0.647), immunosuppressive therapy (P 0.674) and crowding (P 0.872). Conclusion: The TST positivity rate was high among our students; it correlates with in-hospital training stage. More attention should be paid to prevention strategies in medical students prior to and during their clinical training.

The Affecting Factors and Comparison of Tuberculin Skin Test in Peritoneal Dialysis and Hemodialysis Patients

Compared with the general population, patients with chronic renal failure have increased tuberculosis (TB) prevalence and mortality rates. In this study, we aimed to investigate tuberculin skin test (TST) positivity rates in hemodialysis (HD) and peritoneal dialysis (PD) patients and the factors influencing TST positivity. Ninety-two HD patients and 44 PD patients who had been on HD and PD treatment for at least 3 months were recruited into the study. TST was administered in all patients. Positivity was defined as an induration diameter >10 mm. At least 5 mm of induration following skin testing together with a chest radiography indicating previous infection was defined as latent TB infection. TST positivity rates, diameter of TST indurations, and serum albumin levels in HD patients were higher than the PD patients. TST induration size was not correlated with any other parameters in both HD and PD groups. TST-positive patients had higher albumin levels and lower leukocyte count than the TST-negative patients. In TST-positive patients, albumin level was correlated with the duration of dialysis but TST induration size was not correlated with the lymphocyte count and albumin level. In our study, TST positivity of patients was found in 30.4% of HD patients, 9% of PD patients, and 23.5% of total patients. It is still recommended to use TST for the screening test of TB. We found a significant relationship between TST and albumin level. It should be remembered that TST response may be lower in PD patients, especially in cases in which TB is suspected.

Quantiferon-TB Gold in tube assay for the screening of tuberculosis before and during treatment with tumor necrosis factor alpha antagonists

IntroductionThe usefulness of interferon-gamma (IFN-γ) release assays for tuberculosis screening before tumor necrosis factor-alpha (TNF-α) antagonists and for monitoring during treatment is a contraversial issue. The aims of this study were to determine whether TNF-α antagonists affect the results of the Quantiferon-TB Gold in-tube assay (QTF); to assess how QTF performs in comparison with the tuberculin skin test (TST) in rheumatoid arthritis (RA) patients who are about to start treatment with TNF-α antagonists, RA patients who are not candidates for treatment with TNF-α antagonists, rheumatology patients with confirmed current or past tuberculosis infection, and healthy controls, and to determine the specificity of the QTF test to differentiate leprosy patients, another group of patients infected with mycobacteria.MethodsThe 38 RA patients who were prescribed TNF-α antagonists, 40 RA patients who were not considered for TNF-α antagonist use, 30 rheumatology patients with a history or new diagnosis of tuberculosis, 23 leprosy patients, and 41 healthy controls were studied. QTF and TST were done on the same day, and both were repeated after a mean of 3.6 ± 0.2 months in patients who used TNF-α antagonists.ResultsTreatment with TNF-α antagonists did not cause a significant change in the QTF or TST positivity rate (34% versus 42%; P = 0.64; and 24% versus 37%; P = 0.22). Patients with leprosy had a trend for a higher mean IFN-γ level (7.3 ± 8.0) and QTF positivity (61%) than did the other groups; however, the difference was not significant (P = 0.09 and P = 0.43).ConclusionsTreatment with TNF-α antagonists does not seem to affect the QTF test to an appreciable degree. The higher IFN-γ levels in leprosy patients deserves further attention.

The prevalence of tuberculin skin test positivity and the effect of BCG vaccinations on tuberculin induration size in the eastern Mediterranean region of Turkey

To evaluate the prevalence of tuberculin skin test (TST) positivity in Kahramanmaraş and interpret the size of purified protein derivative (PPD) induration with respect to the number of Bacillus Calmette-Guerin (BCG) scars and other factors. Materials and methods: A total of 2979 school children between the ages of 7 and 17 years were evaluated. On the basis of socioeconomic levels, 11 schools were selected and categorized into 3 subgroups: schools in the suburbs of the city (Group 1), schools in the city center (Group 2), and private schools (Group 3). Children were injected with 5 TU/0.1 mL of PPD and the sizes of induration were measured after 72 h. The number of BCG scars and the sizes of induration were recorded for each pupil. Results: The TST was positive in 6.3% of the nonvaccinated students and in 7.5% of the vaccinated students (P > 0.05). The number of BCG vaccination scars was 0 in 174 children (5.8%), 1 in 1232 children (41.4%), 2 in 1516 children (50.9%), 3 in 54 children (1.8%), and 4 in 3 children (0.1%). The mean diameter of the size of the PPD induration for 0, 1, 2, 3, and 4 BCG vaccinations was 2.50 ± 4.05 mm, 5.60 ± 5.11 mm, 8.49 ± 5.09 mm, 8.46 ± 4.38 mm, and 7.66 ± 6.80 mm, respectively. The size of the induration was greatest in students vaccinated twice (P < 0.05). The TST positivity rate was highest in children 11-13 years of age (P < 0.05). Conclusion: The BCG vaccination rate was higher in Kahramanmaraş, whereas the TST positivity rate was lower. The factors that affected the size of the PPD induration were the number of vaccination scars and the age of the subject.

Trends of tuberculin skin test positivity rate among schoolchildren in Attica, Greece

We sought to estimate the prevalence and temporal trends of tuberculin skin test (TST) positivity rate among schoolchildren, in a suburban area of Attica, Greece. We retrospectively analysed the prevalence of the TST positivity (forearm volar surface induration >10 mm) of schoolchildren, in the catchment area of the public primary healthcare centre of Vari, over a 16-y period (1990-2005). TSTs were performed in the context of a national, government-directed TB screening programme. We retrieved 11,105 records of TSTs performed on children aged 6 and 14 y. These tests referred to 7920 and 2969 BCG unvaccinated and vaccinated children, respectively, as well as 120 children who had close contact with a TB confirmed case, and 6 children with known active or latent TB. The prevalence of TST positivity among BCG unvaccinated children was 2.0% over the whole study period; this figure declined in the second compared to the first half of the study period (2.4% vs 1.4%, p<0.001). The gradual decline in TST positivity among BCG unvaccinated schoolchildren, despite the substantial rise in the number of immigrants in Greece, over our study period, may, at least in part, be attributed to relevant national screening and prevention measures.

Tuberculin skin test conversion and reactivity rates among adults with and without human immunodeficiency virus in urban settings in Ethiopia.

To investigate whether low CD4+ T-cell counts in healthy and human immunodeficiency virus (HIV)-infected Ethiopians influence tuberculosis (TB) immunological memory, tuberculin skin test (TST) conversion and reactivity rates were investigated among adults with and without HIV infection in urban settings in Ethiopia. Reaction to the TST was analyzed with purified protein derivative by the Mantoux technique. A total of 1,286 individuals with TST results of > or = 5-mm (n = 851) and < or = 4-mm (n = 435) induration diameters were included. Individuals with < or = 4-mm induration sizes were followed up for 21.4 +/- 9.5 months (mean +/- standard deviation) to observe skin test conversion. The overall TST reactivity (> or = 5-mm induration diameter) was 66.2% (n = 851). Reactivity was significantly lower among HIV-positive persons (40.5%) than among HIV-negative persons (68.7%) (P < 0.001). Of the above persons, 32 incident TB patients were checked for their TST status 13.05 +/- 11.1 months before diagnosis and reactivity was found among 22 (68.7%) of them. Of the TST-negative persons with 0- to 4-mm indurations who were followed up for 3 years, the conversion rate to positivity was 17.9/100 person-years of observation (PYO) (14.4/100 PYO and 18.3/100 PYO in HIV-positive and -negative persons, respectively). Despite lower absolute CD4+ T-cell numbers in Ethiopians, higher TST conversion and reactivity rates show the presence of a higher rate of latent TB infection and/or transmission. The lower TST positivity rate before a diagnosis of TB disease showed the lower sensitivity of the test. This indicates the need for other sensitive and specific diagnostic and screening methods to detect TB infection, particularly among HIV-positive persons, so that they can be given prophylactic isoniazid therapy.

Correlating Two-Step Tuberculin Skin Test Positivity Rates in New Employees with Mycobacterium tuberculosis Disease in Veterans Health Administration Medical Centers Nationwide

BACKGROUND/OBJECTIVES: Healthcare facilities remain a potential risk environment where transmission of Mycobacterium tuberculosis disease (TB) will occur. As Mtb cases decrease in the United States, more emphasis is being placed on latent tuberculosis infection. The Veterans Health Administration (VHA) is a national healthcare system with over 4 million patients seen during the last year, for which approximately 600,000 inpatient admissions occurred and over 35 million outpatient visits. VHA employs over 200,000 individuals, has countless volunteers, and provides an educational venue for a significant proportion of healthcare trainees nationwide. One means to identify latent tuberculosis infection and prevent potential for transmission is by identifying employee/volunteers who are infected at initiation of employment and ensuring preventive therapy if appropriate, including two-step Tuberculin skin testing (TST) for certain persons. The VHA provides an opportunity to assess correlation of two-step TST, preemployment positivity, and occurrence of TB disease in patients. METHODS: Through an electronic, annual census instrument, the VHA has followed TB among patients since federal fiscal year (FY) 1991 and varied components of TST programs since 1993. RESULTS: In the VHA, between FY 1992 and FY 2001, TB, multidrug-resistant (MDR) TB, HIV-associated TB, and MDR-TB with HIV have all significantly decreased over time (p<0.0004 for all). Total TB cases fell from 781 in FY 1992 to 306 in FY 2001. Nationally, for FYs 2000 and 2001, the number of new VHA employees/volunteers was reported at approximately 37,500 and approximately 43,500, of whom approximately 32,000 and approximately 35,000, respectively, met criteria for pre-employment TSTing. During this time period, the number of two-step TSTing of new employees/volunteers was reported at 13,465 and 14,245, respectively; positivity for the second step was 163 (1.21%) and 200 (1.40%), respectively. Correlation coefficients examining the general association between the number of TB cases in patients and both number of positive two-step TSTs and percent of positive two-step TSTs among employees indicates a positive relationship with r=0.37 (p=0.0364) and r=0.19 (p=0.0061), respectively (i.e., as the number of TB cases increases so do the number or percent of positive two-step TSTs). CONCLUSIONS: These data suggest an association between cases of TB among patients treated within healthcare facilities and two-step TST positivity among employees/volunteers during pre-employment examination. This may represent community background rates of positivity on two-step TSTing.

Correlating Two-Step Tuberculin Skin Test Positivity Rates in New Employees with Mycobacterium tuberculosis Disease in Veterans Health Administration Medical Centers Nationwide

Correlating Two-Step Tuberculin Skin Test Positivity Rates in New Employees with Mycobacterium tuberculosis Disease in Veterans Health Administration Medical Centers Nationwide

Status of tuberculosis infection control programs at United States hospitals, 1989 to 1992

Background: Recent nosocomial outbreaks have raised concern about the risk of Mycobacterium tuberculosis transmission in United States hospitals. Methods: To determine current tuberculosis (TB) infection control practices, we surveyed a sample of approximately 3000 acute care facilities about the number of patients with drug-susceptible or multidrug-resistant TB (MDR-TB), health care worker (HCW) tuberculin skin test (TST) results, and compliance with the 1990 Centers for Disease Control and Prevention (CDC) TB guidelines. Analyses were restricted to one response per hospital. Results: Personnel at 1494 (49.8%) hospitals returned a completed survey. Respondent hospitals had a mean of 881 HCWs (range 8 to 10,000) and 196 (range 6 to 2450) beds; 62% percent were community nonteaching hospitals. Of respondent hospitals providing data for 1989 through 1992, the proportion that cared for patients with tB or MDR-TB increased from 46.4% to 56.6% and 0.8% to 4.5%, respectively. The pooled mean HCW TST positivity rate at hire rose from 0.95% to 1.14%, and the pooled mean HCW TST conversion rate increased from 0.40% to 0.51%. In 1992, when we compared hospitals with zero, one to five, or six or greater patients with TB, the risk of a positive HCW TST result at hire or at routine testing significantly increased with increasing number of patients with TB. From 1989 through 1992, the number of hospitals reporting the use of surgical masks for HCW respiratory protection decreased from 96.8% to 66.8%. In 1992, 66% of the hospitals reported compliance with four or more of the AFB isolation room criteria specified in the 1990 CDC TB guidelines. Conclusions: Contrary to prior surveys, this study shows that many U.S. community hospitals admit patients with TB less frequently than do teaching hospitals, and infrequently admit patients with MDR-TB. Because the risk of HCW TST conversion varies with hospital characteristics, these data show the importance of performing a risk assessment, as recommended in the CDC TB guidelines, for each ward and hospital so that TB control measures can be individualized.