Tuberculin skin testing among healthcare workers in the University of Malaya Medical Centre, Kuala Lumpur, Malaysia.

OBJECTIVES: To determine the occupational risk of Mycobacterium tuberculosis infection among healthcare workers (HCWs) and to examine the utility of tuberculin skin testing in a developing country with a high prevalence of bacille Calmette-Guerin vaccination. DESIGN: Tuberculin skin test (TST) survey. SETTING: A tertiary-care referral center and a teaching hospital in Kuala Lumpur, Malaysia. PARTICIPANTS: HCWs from medical, surgical, and orthopedic wards. INTERVENTION: Tuberculin purified protein derivative RT-23 (State Serum Institute, Copenhagen, Denmark) was used for the TST (Mantoux method). RESULTS: One hundred thirty-seven (52.1%) and 69 (26.2%) of the HCWs tested had indurations of 10 mm or greater and 15 mm or greater, respectively. Medical ward HCWs were at significantly higher risk of a positive TST reaction than were surgical or orthopedic ward HCWs (odds ratio, 2.18; 95% confidence interval, 1.33 to 3.57; P = .002 for TST positivity at 10 mm or greater) (odds ratio, 2.61; 95% confidence interval, 1.44 to 4.70; P = .002 for TST positivity at 15 mm or greater). A previous TST was a significant risk factor for a positive TST reaction at either 10 mm or greater or 15 mm or greater, but a duration of employment of more than 1 year and being a nurse were only significantly associated with a positive TST reaction at a cut-off point of 15 mm or greater. CONCLUSIONS: HCWs at the University of Malaya Medical Centre had an increased risk for M. tuberculosis infection that was significantly associated with the level of occupational tuberculosis exposure. A TST cut-off point of 15 mm or greater may correlate better with M. tuberculosis infection than a cut-off point of 10 mm or greater in settings with a high prevalence of bacille Calmette-Guerin vaccination.     

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.     

High rate of negative results of tuberculin and QuantiFERON tests among individuals with a history of positive skin test results.

OBJECTIVES: To evaluate individuals at high risk for tuberculosis exposure who had a history of a positive tuberculin skin test (TST) result in order to determine the prevalence of unsuspected negative TST results. To confirm these findings with the QuantiFERON-TB test (QFT), an in vitro whole-blood assay that measures tuberculin-induced secretion of interferon-gamma. METHODS: This survey was conducted from November 2001 through December 2003 at 3 sites where TST screening is regularly done. Detailed histories and reviews of medical records were performed. TSTs were placed and read by 2 experienced healthcare workers, and blood was drawn for QFT. Any subject with a negative result of an initial TST during the study (induration diameter, <10 mm) underwent a second TST and a second QFT. The TST-negative group comprised individuals for whom both TSTs had an induration diameter of <10 mm. The confirmed-negative group comprised individuals for whom both TSTs yielded no detectable induration and results of both QFTs were negative. RESULTS: A total of 67 immunocompetent subjects with positive results of a previous TST were enrolled in the study. Of 56 subjects who completed the TST protocol, 25 (44.6%; 95% confidence interval [CI], 31.6%-57.6%) were TST negative (P<.001). Of 31 subjects who completed the TST protocol and the QFT protocol, 8 (25.8%; 95% CI, 10.4%-41.2%) were confirmed negative (P<.005). CONCLUSIONS: A significant proportion of subjects with positive results of a previous TST were TST negative in this study, and a subset of these were confirmed negative. These individuals' TST status may have reverted or may never have been positive. It will be important in future studies to determine whether such individuals lack immunity to tuberculosis and whether they should be considered for reentry into tuberculosis screening programs.     

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.     

Challenges to tuberculin screening and follow-up in an urban Aboriginal sample in Montreal, Canada

We sought to describe the prevalence and predictors of tuberculin skin test (TST) reactors in a high-risk sample of urban Aboriginal people, and to evaluate adherence to medical evaluation and latent tuberculosis infection (LTBI) treatment among those with TST reactivity. Of the 164 participants tested, 86% returned for TST reading. Positive TST reactions (>or=10 mm) were observed in 17.7% (25/141, 95% CI 11.4-24.0) of participants, and were associated with older age (OR per 10 year increase 1.8, 95% CI 1.2-2.7) and Inuit Aboriginal group (OR 2.8, 95% CI 1.1-7.3). Only four participants presented for evaluation, of whom one initiated and none completed LTBI treatment. Tuberculin screening in this population can be an effective strategy for identifying TST reactive individuals; however, screening efforts will have minimal impact without additional efforts in this high-risk group.     

Latent tuberculosis in nursing professionals of a Brazilian hospital

Tuberculosis (TB) is considered an occupational disease among health-care workers (HCWs). Direct contact with TB patients leads to an increased risk to become latently infected by Mycobacterium tuberculosis. The objective of this study is to estimate the prevalence of latent M. tuberculosis minfection among nursing professionals of a hospital in Rio Grande do Sul, Brazil, assessed by tuberculin skin test (TST). From November 2009 to May 2010, latent M. tuberculosis infection was assessed by TST in 55 nursing professionals. Epidemiological information was collected using a standardized questionnaire. A positive TST result (> or = 10 mm) was observed in 47.3% of the HCWs tested. There was no significant difference in TST positivity when duration of employment or professional category (technician or nurse) was evaluated. The results of this work reinforce the need for control measures to prevent latent M. tuberculosis infection among nursing professionals at the hospital where the study was conducted.     

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。     

Is tuberculin skin testing useful to diagnose latent tuberculosis in BCG-vaccinated children?

BACKGROUND: The tuberculin skin test (TST) is the most commonly used tool to detect infection with Mycobacterium tuberculosis. We sought to determine whether tuberculin skin testing is useful to detect latent infection by M. tuberculosis in a population that was vaccinated with the Bacille Calmette Guérin (BCG) vaccine. METHODS: We performed a cross-sectional study during October 2000-February 2001, enrolling first and sixth graders from a random, stratified sample of public elementary schools in Orizaba, Veracruz, Mexico. We assessed the relationship between sociodemographic and epidemiological information, BCG scars, and TST reactivity. RESULTS: There were 858 children enrolled in the study with a completed questionnaire and TST result. The prevalence of a positive TST result (> or =10 mm) was 12.4%. Controlling for BCG scar, age, and other characteristics, close contact with pulmonary tuberculosis patients (odds ratio 6.56, 95% confidence interval 2.05-21.07, P = 0.001) was independently associated with TST reactivity. CONCLUSIONS: TST results helped identify children in a BCG-vaccinated population who had recent exposure to persons with pulmonary tuberculosis, were probably infected with M. tuberculosis, and could benefit from treatment for their latent tuberculosis infection.     

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.     

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.     

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。     

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.     

Screening Latino adolescents for latent tuberculosis infection (LTBI)

OBJECTIVES: To investigate the rates of latent TB infection (LTBI) in a sample of young people in San Diego County and examine potential predictors of a positive tuberculin skin test (TST). METHODS: Latino and foreign-born students from ten public middle and high schools were invited to screenings along with a random 10% sample of all other students. After obtaining parental consent, Mantoux tests were placed (N=2,698) and read (n=2,667 [98.9%]) in 48-72 hours. A positive TST was defined as > or =10 mm induration. The mean age of the sample was 14.34 years (SD=1.81); 50.1% were female (n=1,353); 78.5% were Latino (n=2,108); 35.7% were foreign-born (n=939); and 44.3% were uninsured (n=930). RESULTS: The positive TST rate for Latinos was 21.8% vs. 5.6% for non-Latinos, p<0.001. Foreign-born Latinos had the highest infection rate (31.3%), followed by foreign-born non-Latinos (20.4%), U.S.-born Latinos (15.4%), and U.S.-born non-Latinos (1.0%), p<0.001. Logistic regression was conducted to determine predictors of TST positivity. Being Latino (odds ratio [OR]=3.27), uninsured (OR=1.60), foreign-born (OR=3.90), and living in the south county region closest to the U.S./Mexico border (OR=2.72) were significant predictors. CONCLUSIONS: Results suggest that Latino youth near the California/Mexico border are at high risk for infection, for remaining undiagnosed, and for being under-treated for LTBI.     

Prevalence of malnutrition in patients in general practice

The objective of this study was to determine the prevalence and correlates of malnutrition in patients living at home with cancer and chronic diseases. Patients (213) with cancer and 228 patients with chronic diseases were randomly selected from general practice registers. Nutritional status was determined from body mass index (BMI in kg/metre2), triceps skinfold thickness (TST), mid-arm muscle circumference (MAMC) and population centiles. Patients were classified as mildly malnourished if they had a BMI < 20 and TST or MAMC < 15th centile, moderately malnourished if they had a BMI < 18 and TST or MAMC < 5th centile, and severely malnourished if they had a BMI < 16 and TST or MAMC < 5th centile. Using these criteria, nearly 10% of patients were malnourished: 24 (5.4%) mildly, 12 (2.7%) moderately and 4 (0.01%) severely. Malnutrition was more common in patients in social classes 3.2, 4 and 5 than in social classes 1, 2 and 3.1 (P = 0.003), and in patients receiving district nurse care (P < 0.001). Malnutrition was more prevalent in cancer patients who complained of chronic or severe pain (32% vs 12%, P = 0.021) and in patients with chronic disorders who experienced mental apathy (22% vs 5%, P = 0.014). Clinicians need to be aware that malnutrition is common in patients living at home. In this study BMI proved to be a fairly good indicator of malnutrition and routine measurement of BMI would be one simple way of detecting patients who are at risk.     

Neonatal Bacille Calmette-Guérin vaccination and tuberculin skin test reactions at 2- and 6-months: Effects on mortality up to 1 year of age

BackgroundIn randomized trials, Bacille Calmette-Guérin (BCG) vaccine has been associated with reduced all-cause mortality. BCG-induced Tuberculin Skin Test (TST) reactions have also been associated with reduced all-cause mortality. We aimed to assess the association between TST responses and subsequent mortality in three birth cohorts and conducted a meta-analysis of existing studies.MethodsObservational study within three Guinea-Bissau BCG trial birth cohorts (conducted 2002–04, 2009–2013 and 2014–18) that encompassed children who were BCG-vaccinated within 28 days with TSTs performed at 2- (n = 1389) and 6-months (n = 2635) of age. We evaluated TST reaction determinants by binomial regression and assessed the association between TSTs > 1 mm (reactors) vs. ≤ 1 mm (non-reactors) and subsequent mortality risk up to age 12 months in Cox-models providing Mortality Rate Ratios (MRRs). We searched PubMed for studies to calculate meta-estimates of the association between TST reactivity by age 2- and 6-months and all-cause mortality.ResultsLarge post-vaccination wheal size was associated with 6-month TST positivity and so was receiving BCG-Denmark or BCG-Japan, compared with BCG-Russia. By age 2 months, 22% (302/1389) of infants were TST reactors with a 2–12-month mortality risk of 1.7% (5/302) vs. 3.3% (36/1087) for non-reactors, the corresponding reactor/non-reactor MRR = 0.49 (0.19–1.26). By age 6 months, 44% (1149/2635) of infants were reactors and the 6–12-month mortality risk was 0.4% (4/1149) vs. 0.6% (9/1486) for non-reactors, the MRR = 0.87 (0.27–2.86). The literature search provided 3 studies. The meta-analysis revealed a uniform pattern of reduced mortality associated with TST reactivity, a TST response by 2 months being associated with an MRR of 0.59 (0.39–0.90); for 6-month TST responses the MRR was 0.65 (0.43–1.00).ConclusionAmong BCG-vaccinated infants, TST reactions were associated with markedly reduced mortality. Improved vaccination technique and using certain BCG strains could lead to a higher TST reaction prevalence, which would enhance BCG’s beneficial non-specific effects.     

Comparison of tuberculin skin test response after three modalities of neonatal BCG vaccination

The aim of this study was to determine the tuberculin skin test (TST) response to three different BCG modalities [0.1 ml Tokyo (n=104), 0.05 ml Pasteur-Mérieux (n=137) and 0.1 ml Pasteur-Mérieux (n=100)] in a cohort of healthy newborns 5 months after vaccination at birth in Santiago, Chile. Among the 341 infants, 91.2% had a response to TST, and the mean+/-SD TST reaction size was significantly larger in infants receiving the Tokyo strain than in those receiving the 0.05 ml or 0.1 ml Pasteur-Mérieux strains (4.4+/-2.0, 3.5+/-1.3 and 3.1+/-1.4 mm, respectively; P<0.0001). The mean+/-SD of the BCG scar size was significantly lower in infants vaccinated with the Tokyo strain than in those vaccinated with the 0.1 ml Pasteur-Mérieux strain (3.9+/-1.2 vs. 4.3+/-1.1 mm; P=0.03) and no significant difference was found between infants receiving the Tokyo strain and the 0.05 ml Pasteur-Mérieux strain. However, the differences in TST size induced by diverse BCG vaccination modalities may not reflect the quality of the immunologically induced response in terms of TB protection.     

2～14岁赴美移民申请人结核病筛查结果分析

〔目的〕对2~14岁赴美移民申请人结核病筛查的结果进行分析,为早期发现潜伏结核感染、肺结核患者及结核病防控提供参考依据。〔方法〕对2009年7月—2010年3月期间在广东国际旅行卫生保健中心体检的2747名2~14岁赴美移民申请人进行结核病筛查,所有申请人均进行结核菌素皮试(TST);若TST≥10mm或申请人有疑似结核的体征或症状,应进行X线胸片检查;若胸片所见疑似结核或有疑似结核的体征或症状的,进行结核分枝杆菌实验室检测。〔结果〕TST皮试结果显示阳性率为47.40%,阴性率52.60%,其中中度阳性者624名,占总人数的22.72%,强阳性者25名,占总人数的0.91%。阴性率随年龄增长逐渐下降,阳性与中度阳性率随年龄增长逐渐上升(P0.001)。649名TST≥10 mm者胸片检查结果发现,疑似结核病患者8人,其中非领养儿童1例,领养儿童7例。结核分枝杆菌实验室检测结果发现,8例疑似肺结核患者中,1例为耐多药结核患者。〔结论〕加强儿童,特别是生活条件和营养条件差的儿童结核病的筛查,提高卡介苗覆盖率及接种质量对于儿童肺结核的防控具有重要意义。     

应用酶联免疫斑点法快速诊断儿童结核分枝杆菌感染的研究

目的:探讨基于ESAT-6和CFP-10抗原肽的酶联免疫斑点技术(Enzyme-link immunospot essay,ELISPOT)在临床实践中诊断儿童结核分枝杆菌感染的临床价值。方法:应用ELISPOT技术检测14例确诊的儿童肺结核病例和16例健康儿童对照的外周血单个核细胞的INF-γ,同时对所有研究对象实施结核菌素皮肤实验(Tuberculin Skin Test,TST),探讨ELIS-POT技术在快速诊断儿童结核分枝杆菌感染的临床应用价值。结果:ELISPOT灵敏度为85.7%(95%CI:60.1～95.0),特异度为93.8%(95%CI:71.7～98.9)。TST灵敏度为71.4%(95%CI:45.4～88.3),特异度为56.3%(95%CI:33.2～76.9)。ELISPOT的灵敏度高于TST,但无统计学意义(P>0.05)。ELISPOT的特异度显著高于TST(P<0.05)。ELISPOT和TST检测结果总一致性较差(κ=0.35)。在活动型结核病组中,ELISPOT和TST一致性较差(κ=0.18),类似地,在对照组中,ELIS-POT和TST一致性也较差(κ=0.16)。不一致的检测结果在病例组中常见ELISPOT阳性而TST阴性(3例),而在对照组中常见于ELISPOT阴性而TST阳性(7例)。结论:ELISPOT诊断儿童活动性结核病准确性高于TST。ELISPOT具有较高的诊断灵敏度和特异度,其特异度不受儿童的卡介苗接种的影响,适合作为临床诊断儿童结核分枝杆菌感染的辅助诊断技术,有助于感染的儿童得到更快速的诊断和治疗。     

Outbreak of Pulmonary Tuberculosis in a Chinese High School, 2009–2010

Background

In February 2009, a high school student was diagnosed with sputum-smear positive pulmonary tuberculosis (TB). One year later, 2 other students in the same grade developed sputum-smear positive TB.

Methods

We used tuberculin skin testing (TST), chest radiography, sputum smear, and symptomatology for case identification. We defined latent TB infection (LTBI) as a TST induration of 15 mm or larger, probable TB as a chest radiograph indicative of TB plus productive cough/hemoptysis for at least 2 weeks or TST induration of 15 mm or larger, and confirmed TB as 2 or more positive sputum smears or 1 positive sputum smear plus a chest radiograph indicative of TB.

Results

Of students in the same grade as the primary case-student, 26% (122/476) had LTBI and 4.8% (23/476) had probable/confirmed TB. Of teachers, 43% (18/42) had LTBI and none had probable/confirmed TB. Sharing a classroom with the primary case-student increased risk for LTBI (rate ratio = 2.5; 95% CI: 1.9–3.4) and probable/confirmed TB (rate ratio = 17, 95% CI: 7.8–39). Of students with LTBI in February 2009 who refused prophylaxis, 50% (11/22) had probable/confirmed TB in April 2010.

Conclusions

This TB outbreak was likely started by delayed diagnosis of TB in the case-student and was facilitated by lack of post-exposure chemoprophylaxis. Post-exposure prophylaxis is strongly recommended for all TST-positive students.Key words: epidemiology, outbreak, students, tuberculosis     

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.