Factors associated with tuberculin reactivity in two general hospitals in Mexico.

OBJECTIVE: To identify risk factors associated with tuberculin reactivity in healthcare workers (HCWs). DESIGN: Cross-sectional survey of tuberculin reactivity (2 TU of purified protein derivative (PPD) RT23, using the Mantoux two-step test). SETTING: Two general hospitals located in a region with a high prevalence of tuberculosis and high bacille Calmette-Guerin (BCG) coverage. PARTICIPANTS: Volunteer sample of HCWs. RESULTS: 605 HCWs were recruited: 71.2% female; mean age, 36.4 (standard deviation [SD], 8.2) years; 48.9% nurses, 10.4% physicians, 26.8% administrative personnel; mean time of employment, 10.9 (SD, 6.7) years. PPD reactivity (> or =10 mm) was found in 390 (64.5%). Multivariate analysis revealed an association of tuberculin reactivity with occupational exposure in the hospital: participation in autopsies (odds ratio [OR], 9.3; 95% confidence interval [CI95], 2.1-40.5; P=.003.), more than 1 year of employment (OR, 2.4; CI95, 1.1-5.0; P=.02), work in the emergency or radiology departments (OR, 2.0; CI95, 1.03-3.81; P=.04), being physicians or nurses (OR, 1.5; CI95, 1.04-2.11; P=.03), age (OR, 1.04; CI95, 1.02-1.07 per year of age; P<.001), and BCG scar (OR, 2.1; CI95, 1.2-3.4; P=.005). CONCLUSIONS: Although the studied population has a high baseline prevalence of tuberculosis infection and high coverage of BCG vaccination, nosocomial risk factors associated with PPD reactivity were identified as professional risks; strict early preventive measures must be implemented accordingly.     

Risk factors for positive tuberculin skin test in Guinea-Bissau

BACKGROUND: The tuberculin skin test is used for tracing of tuberculosis transmission and identifying individuals in need of prophylactic treatment. METHODS: Using a case-control study design, we recruited 220 smear-positive tuberculosis cases and 223 randomly selected healthy community controls in Bissau, Guinea-Bissau, during 1999-2000. Tuberculin skin tests were performed on family members of cases and controls (n = 1059 and n = 921, respectively). Induration of 10 mm or greater was considered positive. Risk factors were calculated for children (<15 years) and adults separately in multivariate logistic regression analysis. RESULTS: The prevalence of positive tuberculin skin test was 41% in case-contacts compared with 22% in control-contacts, resulting in a prevalence ratio of 1.48 (95% confidence interval = 1.37-1.60). Positive skin tests among case-contacts increased with age for children, as well as with proximity to a case during the night, for both children and adults. A Bacille Calmette Guerin scar increased the likelihood of having a positive tuberculin skin test for adults in case households, but not in other categories of contacts. Among control-contacts the prevalence of positive skin test was associated with older age in children, history of tuberculosis in the family, and a positive tuberculin skin test of the control person. CONCLUSIONS: Risk factors for a positive tuberculin skin test among case- and control-contacts are closely related to tuberculosis exposure. Having a BCG scar did not increase the risk of positive skin test in unexposed individuals. Tuberculin skin testing remains a useful tool for diagnosing tuberculosis infection.     

Tuberculin reactivity in a population of schoolchildren with high BCG vaccination coverage.

OBJECTIVE: To investigate the influence of BCG vaccination or revaccination on tuberculin skin test reactivity, in order to guide the correct interpretation of this test in a setting of high neonatal BCG vaccination coverage and an increasing BCG revaccination coverage at school age. METHODS: We conducted tuberculin skin testing and BCG scar reading in 1 148 children aged 7-14 years old in the city of Salvador, Bahia, Brazil. We measured the positive effect of the presence of one or two BCG scars on the proportion of tuberculin skin test results above different cut-off levels (induration sizes of > or = 5 mm, > or = 10 mm, and > or = 15 mm) and also using several ranges of induration size (0, 1-4, 5-9, 10-14, and > or = 15 mm). We also measured the effects that age, gender, and the school where the child was enrolled had on these proportions. RESULTS: The proportion of tuberculin results > or = 10 mm was 14.2% (95% confidence interval (CI) = 8.0%-20.3%) for children with no BCG scar, 21.3% (95% CI = 18.5%-24.1%) for children with one BCG scar, and 45.0% (95% CI = 32.0%-58.0%) for children with two BCG scars. There was evidence for an increasing positive effect of the presence of one and two BCG scars on the proportion of results > or = 5 mm and > or = 10 mm. Similarly, there was evidence for an increasing positive effect of the presence of one and two scars on the proportion of tuberculin skin test results in the ranges of 5-9 mm and of 10-14 mm. The BCG scar effect on the proportion of results > or = 5 mm and > or = 10 mm did not vary with age. There was no evidence for BCG effect on the results > or = 15 mm. CONCLUSIONS: In Brazilian schoolchildren, BCG-induced tuberculin reactivity is indistinguishable, for results under 15 mm, from reactivity induced by Mycobacterium tuberculosis infection. BCG revaccination at school age increases the degree of BCG-induced tuberculin reactivity found among schoolchildren. This information should be taken into account in tuberculin skin test surveys intended to estimate M. tuberculosis prevalence or to assess transmission patterns as well as in tuberculin skin testing of individuals used as an auxiliary tool in diagnosing tuberculosis. Taking this information into consideration is especially important when there is increasing BCG revaccination coverage.     

Effect of high-dose vitamin A supplementation on the immune response to Bacille Calmette-Guerin vaccine

BACKGROUND: Vitamin A supplementation (VAS) at birth has been associated with decreased mortality in Asia. Bacille Calmette-Guérin (BCG) vaccine is given at birth in tuberculosis-endemic countries. Previous studies suggest that VAS may influence the immune response to vaccines. OBJECTIVE: Our objective was to examine whether VAS influences the immune response to simultaneously administered BCG vaccine. DESIGN: Within a randomized trial of 50,000 IU vitamin A or placebo given with BCG vaccine at birth in Guinea-Bissau, 2710 infants were examined for BCG scar formation and delayed-type hypersensitivity (DTH) to purified protein derivative of Mycobacterium tuberculosis (PPD) at 2 and 6 mo of age. The ex vivo cytokine response to PPD was measured in 607 infants. RESULTS: At 2 mo of age, 39% (43% of the boys and 34% of the girls) responded to PPD. The prevalence ratio of a measurable PPD reaction for VAS compared with placebo recipients was 0.90 (95% CI: 0.80, 1.02) for all infants, 0.81 (95% CI: 0.69, 0.95) for boys, and 1.04 (95% CI: 0.86, 1.26) for girls. At 6 mo of age, 42% of the infants responded to PPD. No difference was observed between VAS and placebo recipients. The prevalence of BCG scar was not affected by VAS. The ex vivo interferon-gamma response to PPD was increased by VAS (means ratio: 1.40; 95% CI: 1.03, 1.91). CONCLUSIONS: VAS with BCG vaccination does not appear to interfere with the long-term immune response to BCG. However, VAS temporarily altered the DTH reaction to PPD in boys at 2 mo of age, suggesting sex differences in the immunologic response to VAS given with BCG. This trial was registered at www.clinicaltrials.gov as #NCT00168597.     

Results and significance of a baseline tuberculin skin test programme among health care workers in a hospital setting

BACKGROUND: Due to the resurgence of tuberculosis (Tb), health care workers (HCW) are considered at increased risk for Latent Tuberculosis Infection (LTI). According to the national guidelines health care facilities are required both to perform tuberculin skin tests (TsT) on all employees with potential occupational exposure to Tb and to analyze the results obtained. However, only a limited number of studies can be found in the literature reporting data of Tb prevalence in Italian hospitals. OBJECTIVES: The aim of this study was to determine the prevalence of and the relative risks for positive TsT among employees of the Hospital of Cuneo. METHODS: After informed consent, a questionnaire and a TsT according to the Mantoux technique were administered to the 2368 employees of the hospital exposed to occupational risk for Tb. The variables considered for the univariate and multivariate analysis included several anthropometric, occupational and clinical factors RESULTS: 274 of the 2210 employees who completed the screening programme had positive TsT (12.4%). Only one subject had been treated for active Tb. Factors significantly associated with a positive TsT were duration of employment (odds ratio [OR]:4.90, CI: 2.25-10.66, for length of employment 10-17 years; and OR: 8.77, CI: 3.53-21.81, for length >17 years; p < 0.001); working in a Tb high-risk occupational setting (OR 4.26, CI: 1.90-9.57for level of "limited" risk and OR: 5.68, CI: 2.47-13.07 for level of "medium" risk; p < 0.001); belonging to nurse or assistant nurse job categories (OR: 2.80, CI: 1.09-7.19; p < 0.05); history of active or latent Tb infection (OR: 11.54, CI: 5.54-24.06; p < 0.001); birth in a foreign country (OR: 4.40, CI: 1.30-14.85; p = 0.01); and BCG immunization (OR: 2.51, CI: 1.68-3.75; p < 0.001). Seventeen subjects had a positive reaction after a two-step test (0.8%). Boosting occurred among elderly employees (mean age: 48, 3 +/- 8.0 yrs), with long duration of employment (22, 2 +/- 10.5 yrs), vaccinated with BCG (17/17). CONCLUSIONS: Our data suggest that a baseline survey based on TsT is useful to assess the prevalence of and risk factors for TLI in a health care setting. The high rate of participation in the survey (93.3%) was probably due to the training and awareness efforts aimed specifically at exposed HCW.     

Tuberculous infection in Saharia, a primitive tribal community of Central India

A cross-sectional tuberculin survey was carried out to estimate the prevalence of tuberculous infection and the annual risk of tuberculosis infection (ARTI) among children of Saharia, a primitive ethnic group in Madhya Pradesh, Central India. A total of 1341 children aged 1-9 years were subjected to tuberculin testing with 1 TU of PPD RT 23 and the reaction sizes were read after 72h. The proportion of BCG scar-positive children was 34.6%. The frequency distribution of children by reaction sizes indicated a clear-cut anti-mode at 11mm and a mode at 18mm at the right-hand side of the distribution. The prevalence of infection among children irrespective of BCG scar was estimated as 20.4% (95% CI 18.2-22.5%) and the ARTI was 3.9% (95% CI 3.5-4.3%). The corresponding figures were 21.1% (95% CI 18.3-23.8%) and 3.9% (95% CI 3.4-4.5%) among BCG scar-negative children and 19.0% (95% CI 15.4-22.5%) and 4.0% (95% CI 3.2-4.8%) among BCG scar-positive children. The findings of the present study show a high prevalence of tuberculous infection and high ARTI in this primitive ethnic group. There is an urgent need to further intensify tuberculosis control measures on a sustained and long-term basis in this area.     

Clinical inquiries. How should we manage a patient with a positive PPD and prior BCG vaccination?

Prior bacille Calmette-Guerin (BCG) vaccination increases the likelihood of a positive tuberculosis (TB) 5TU purified protein derivative (PPD) skin test. The PPD response following BCG vaccine varies with age at vaccination, number of years since the BCG vaccination, number of times vaccinated, and number of PPDs performed. An induration of greater than 14 mm is unlikely to be due to prior BCG vaccination (strength of recommendation [SOR]: A, based on meta-analysis of validation cohort studies). The variable reaction after BCG vaccination, along with the desire to detect all cases of TB, has led to recommendations that all patients with a positive PPD test be treated as true positives. These patients should undergo chest radiography and appropriate treatment, regardless of history of BCG vaccine (SOR: B, extrapolation from level 1 study). A recently developed alternative is the interferon-gamma assay (QuantiFERON-TB Gold test), which may be used in place of, or in addition to, the PPD skin test for patients who are known to have received a BCG vaccine (SOR: B, extrapolation from a validation cohort study).     

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

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

2014年湖北省江陵县中心城区小学生PPD试验 结果分析

摘要:目的　了解江陵县在校小学生人群结核病免疫力和结核感染状况,探讨学校结核病防控措施。方法　应用TB-PPD对在校小学生进行皮内试验,72 h观察并判定反应结果,采用描述流行病学方法对试验结果进行分析。结果　接受PPD试验学生2465名,阳性人数为707名,总阳性率28.68%。其中强阳性20名,强阳性率0.81%。男生与女生阳性率分别为27.58%和30.02%,强阳性率分别为0.52%和1.16%,差异均无统计学意义。农村户藉学生阳性率高于城镇户藉学生,两者差异有统计学意义（χ2＝10.10,P值＜0.01）,年级间阳性率差异亦有统计学意义（χ2＝7.52～30.52,P值均＜0.01）。结论　本次调查在校小学生PPD阳转率较低,与新生儿卡介苗接种质量不高和受检人群抗体保护水平随着时间推移抗体减弱均有关,提示接种单位仍要加强新生儿卡介苗规范接种,同时建议各地定期开展学生PPD试验,及早筛查结核病例,提高学校结核病防控效果。     

A study of the association between delayed type hypersensitivity reaction to mycobacterium tuberculosis and atopy in asthmatic children

The purpose of this study was to investigate if there is an inverse association between Mycobacterium tuberculosis infection and atopy among children living in rural and semi urban areas in El Behira governorate, Egypt. METHODS: All the studied children were BCG vaccinated in their newborn period. In Tuberculin testing, indurations greater than or equal to 5 mm were accepted as positive. For atopy, the most common aeroallergens were used in skin intradermal testing, and reactions > or = 3 mm were accepted as positive. RESULTS: Among 150 studied children whose ages ranged from 4-8 years, 89 patients were purified protein derivative (PPD) negative whereas in 61 patients PPD was positive. Among the PPD negative patients skin intradermal test was positive for atopy in 51.6% (n = 46), while among the PPD positive patients skin intradermal test was positive in 52.4% (n = 32). As the two groups were compared for having positive intradermal skin test reaction, no statistically significant difference was detected between them (p >0.05). CONCLUSIONS: In this study no statistically significant difference was detected between Mycobacterium tuberculosis infection as indicated by positive PPD positivity and atopy tested by skin intradermal injection of common aeroallergens.     

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.     

结核病疫情中接触者PPD结果的影响因素研究

目的了解结核疫情中接触者PPD结果的影响因素,为部队疫情防控提供参考依据。方法对结核疫情中的密切接触者进行流行病学调查和PPD试验并分析结果。结果各学员队的患病人数与阳性率和强阳性率呈正相关性,相关系数分别为0.970和0.964;与患者同宿舍的接触者PPD试验强阳性率为34.48%,高于与患者不同宿舍接触者的强阳性率16.16%,二者差异有统计学意义(χ2=13.9539,P0.01);有卡瘢组和无卡瘢组强阳性率分别为21.72%和17.09%,差异无统计学意义(χ2=1.0768,P0.05);居住地在城市的学员强阳性率为16.92%,低于农村的23.81%,差异无统计学意义(χ2=2.812,P0.05)。结论患病人数和同宿舍居住是接触者PPD结果的影响因素;卡介苗和城乡差异不是其影响因素。     

Factors associated with latent tuberculosis infection in the contacts of tuberculosis patients

BACKGROUND: As tuberculosis control programs have reached acceptable levels in the identification and treatment of persons with active tuberculosis, the next step should be to develop methods of preventing new cases. Persons with latent tuberculosis infection (LTI) are considered to have a higher risk of developing active tuberculosis. The objective of this study was to evaluate the prevalence of LTI and its associated factors in the contacts of tuberculosis patients. METHODS: We studied the contacts of tuberculosis patients who were examined in the Center for Tuberculosis Control and Prevention in Lleida (Spain) from 1991-1997. Factors associated with the index case (demographic, radiographic, bacteriologic and therapeutic) and tuberculin skin test results and demographic data in contacts were collected. Data on HIV infection, injection drug use and alcohol consumption in tuberculosis patients were also collected. The associations were assessed by obtaining crude and adjusted odds ratios. RESULTS: The prevalence of LTI among contacts was 36.1% (780/2,161). In the multivariate analysis a higher frequency of LTI was detected in contacts older than 14 years (ORa = 3.34; 95% CI, 2.51-4.45), contacts who had a higher degree of exposure to the index case (ORa = 1.96; 95% CI, 1.59-2.42), contacts of pulmonary tuberculosis patients (ORa = 1.54; 95% CI, 1.01-2.35), contacts of patients with a positive sputum smear (ORa = 1.51; 95% CI, 1.15-1.99), contacts of patients with caverns on chest x-ray (ORa = 1.27; 95% CI, 1.01-1.61) and contacts of patients with delayed treatment (ORa = 1.31; 95% CI, 1.05-1.62). CONCLUSIONS: The overall prevalence of LTI in the contacts of patients with tuberculosis was high. Among the factors studied, delayed treatment in the index case was independently associated with the frequency of LTI in tuberculosis contacts. Measures for the early diagnosis and treatment of tuberculosis should be intensified.     

Prevalence of tuberculosis and HIV infections among participants in an intravenous drug user risk-control program]

BACKGROUND: To determine the prevalence of tuberculosis and HIV infection in addition to the related factors among a population of participants in the risk control program in the town of Lleida. METHODS: The sample was comprised of the newly-enrolled participants in the program in April-June 1996, among whom a questionnaire was handed out for collecting the data concerning the variables involved: age, gender, results of the tuberculin test, BCG vaccination, knowledge of the serology regarding HIV, former imprisonment and number of years having used heroin. The prevalence of the tuberculosis and HIV infection was calculated to a 95% confidence interval (CI). The relating of these two variables to all other variables in the study was determined by means of the odds ratio (OR) and its 95% CI. RESULTS: One hundred and fifty (150) patients were seen, 45 of whom were newly enrolled participants. Eighty percent (80%) were males, averaging 31.1 years of age. The prevalence of this dual infection was 8.9% (95% CI 2.8-22.1). The prevalence of the tuberculosis infection was 27.3% (95% CI 12.4-43.0), being higher among former prison inmates (OR = 3.4; 95% CI 0.5-27.4). The prevalence of the HIV infection was 36.1% (95% CI 21.3-53.8), being greater among those who had been using heroin for longer than 11 years (OR = 7.3; 95% CI 1.0-65.9). CONCLUSIONS: Former imprisonment is the main risk factor for tuberculosis infection. The number of years of heroin use are related to the HIV infection, especially when longer than 11 years. The risk control programs in our country should carry out activities aimed at monitoring tuberculosis and HIV infection.     

Microepidemics of tuberculosis in schools. How should we select contacts?

BACKGROUND: Outbreaks of microepidemics of tuberculosis indicate the existence of Mycobacterium tuberculosis transmission. We describe a microepidemic in a school in which an index case with low infective capacity gave rise to a high percentage of tuberculosis infection and disease in the center. METHODS: Contact investigation was performed in 423 pupils of a school after a recently arrived teacher with few symptoms was diagnosed with tuberculosis. A cross-sectional study was carried out to calculate the prevalence of tuberculosis infection and disease in the school center. RESULTS: Statistically significant differences were found in the distribution of positive results in the first tuberculosis skin test for primary and secondary students, with more positive results in secondary school pupils (18.4%) than in primary school pupils (6.1%). The incidence of skin tuberculosis test converters was 5.7%. The prevalence of infection by educational level was 10% in primary education and 23.4% in secondary education. The risk of infection in secondary school pupils was more than twice that in primary school pupils (OR = 2.4; 95% CI, 1.5-3.5). There were 6 new cases of tuberculosis in pupils. CONCLUSION: The high percentage of conversions in the second tuberculosis skin test indicated the existence of transmission in the school. The results of this study support contact investigation in schools where there is exposure to a case of tuberculosis, whether highly infective or nort.     

Annual tuberculin skin testing of employees at a university hospital: a cost-benefit analysis

The usefulness of routine annual tuberculin skin testing (purified protein derivative [PPD]) of hospital employees has been questioned. Between 1984 and the end of 1987 the PPD conversion rates of hospital employees at a university and psychiatric hospital in North Florida were compared. The number of employees in both hospitals were almost equal and compliance with the annual testing was more than 95%. In the psychiatric hospital tuberculosis screening of patients was practiced on admission and annually thereafter. Although no unsuspected smear-positive tuberculosis patients were diagnosed in the psychiatric hospital as compared to four in the university hospital, the annual conversion rates of employees were 0.42% and 0.13%, respectively (p greater than 0.001). However, the ratios of these conversion rates to the incidence of tuberculosis in the counties where these hospitals are located respectively were similar (20.0 vs 24.3, p = 0.7). The community seems be the major source of the PPD conversion. At the university hospital more than +70,000 was spent on the annual PPD testing to discover 15 converters; nine had no or minimal contact with patients and only two complied with isoniazid (INH) prophylaxis. Annual PPD testing is not cost effective in hospitals with a low annual conversion rate among its employees and with low tuberculosis case rates in the hospital and the surrounding community.     

Tuberculosis infection and disease among schoolchildren: the influence of the HIV epidemic and of other factors

BACKGROUND: The HIV/AIDS epidemic has caused an excess of tuberculosis cases in Spain and in other countries, but its impact on tuberculosis infection is less well understood. This study presents a massive screening undertaken to estimate the prevalence of tuberculous infection in a cohort of primary school entrants. The evolution of the risk of infection is studied by comparison with previous data in the same population. METHODS: Tuberculin skin test screening with 2TU of PPD RT 23 of first grade students in the primary schools of Barcelona, in the 1994-95 school year (cohort born in 1988). Information was also sought from families of unscreened children. Contacts of PPD+ children were traced to locate index cases. The results were also linked to the case registry of the tuberculosis control programme. RESULTS: The prevalence of tuberculin reactors free of BCG vaccination among the 11,080 schoolchildren screened belonging to the 1988 cohort was 0.76%. A 3% annual decline in the annual risk of infection is estimated by comparison with previous data. The identification of 24 cases with a previous history of tuberculosis disease and of 13 cases with active disease diagnosed after the screening was possible by the follow up of these tuberculin positive children and of the information provided by families of unscreened pupils. The screening detected 1.5 new cases of tuberculosis per 1000 tuberculin tests performed. Tuberculosis infection could be traced to HIV infected tuberculosis cases for at least 6% of the positive schoolchildren. CONCLUSIONS: The decline of the annual risk of infection continues in Barcelona, although at a slower pace than before the HIV/AIDS epidemic, probably attributable to the influence of injecting drug users with smear positive tuberculosis and HIV/AIDS.     

Tuberculosis and tuberculin quality: best intentions, misleading results.

OBJECTIVE: To compare the performance of three purified protein derivative (PPD) formulations: Tubersol (Connaught); RT23, Statens Serum Institut (SSI); and RT23, Mexico, tested in Mexican populations at low and high risk for tuberculosis (TB). DESIGN: A double-blinded clinical trial. SETTING: A university hospital in Mexico City. PARTICIPANTS: The low-risk population was first or second-year medical students with no patient contact; the high-risk population was healthcare workers at a university hospital. METHODS: Each of the study subjects received the three different PPD preparations. Risk factors for TB, including age, gender, occupation, bacille Calmette-Guérin (BCG) status, and TB exposure, were recorded. A 0.1-mL aliquot of each preparation was injected in the left and right forearms of volunteers using the Mantoux technique. Blind readings were done 48 to 72 hours later. Sensitivity and specificity were calculated at 10 mm of induration using Tubersol as the reference standard. The SSI tested the potency of the different PPD preparations in previously sensitized guinea pigs. RESULTS: The low-risk population had a prevalence of positive PPD of 26%. In the low-risk population, RT23 prepared in Mexico, compared to the 5 TU of Tubersol, had a sensitivity of 51%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 86%. The RT23 prepared at the SSI had a sensitivity of 69%, a specificity of 99%, a positive predictive value of 95%, and a negative predictive value of 90%. In the high-risk population, the prevalence of positive PPD was 57%. The RT23 prepared in Mexico had a sensitivity of 33%, a specificity of 100%, and a positive predictive value of 53%; the RT23 prepared at the SSI had a sensitivity of 91%, a specificity of 98%, a positive predictive value of 98%, and a negative predictive value of 89%. RT23 used in Mexico had a potency of only 23% of that of the control. There was no statistical association among those with a positive PPD, irrespective of previous BCG vaccination (relative risk, 0.97; 95% confidence interval, 0.76-1.3;P=.78). CONCLUSIONS: Healthcare workers had twice the prevalence of positive PPD compared to medical students. RT23 prepared in Mexico had a low sensitivity in both populations compared to 5 TU of Tubersol and RT23 prepared at the SSI. Previous BCG vaccination did not correlate with a positive PPD. Low potency of the RT23 preparation in Mexico was confirmed in guinea pigs. Best intentions in a TB program are not enough if they are not followed by high-quality control.     

Vaccination technique, PPD reaction and BCG scarring in a cohort of children born in Guinea-Bissau 2000-2002

The rates of positive tuberculin skin test (TST) reactions and BCG scarring after BCG vaccination vary between studies and populations. Tuberculin reactivity and BCG scarring may be related to better child survival in low-income countries. We therefore studied determinants for TST reaction and scarring in Guinea-Bissau. In a cohort of children born in suburban Bissau from March 2000 to July 2002, we assessed a Mantoux test with Purified protein derivative (PPD) (SSI, 2 T.U.) at 2 (2689 children), 6 (N=2148) and 12 months (N=1638) of age, and BCG scar was assessed at 2 (N=2698) and 6 months (N=2225) of age. In a subgroup of the children the vaccination technique was monitored by direct observation of post-vaccination wheal and route of administration. Three different types of BCG vaccine supplied by the local Extended Programme on Immunization were used. At 6 months of age the rate of PPD reactors (>1mm) after BCG vaccination was 25% and the rate of scarring was 89%. One BCG strain was associated with fewer PPD reactors (OR=0.54 (0.31-0.91)) and BCG scars (OR=0.13 (0.05-0.37)) and larger post-vaccination wheals produced more PPD reactions (OR 1.21 (95% CI 1.02-1.43)) and BCG scars (OR 1.66 (1.24-2.21)). In the multivariable analyses of BCG-vaccinated children assessed at 6 months of age, monitoring of vaccination technique and type of BCG vaccine were important. This was not changed by control for other determinants, including sex, season, vaccination place, birthplace, ethnic group, low birth weight, place of residence, education and civil status of mother. We reason that vaccination technique and BCG strain are important for PPD reaction and scarring in response to BCG vaccination. Considering that these responses are associated with better infant survival, the importance of monitoring vaccination technique and of different BCG strains should be evaluated with respect to infant mortality.     

河南省结核病防治机构工作人员结核病感染率调查

目的了解河南省结核病防治机构工作人员结核病感染情况。方法于2005年1月从河南省109个县中随机抽取40个县，对抽取的县及所有市级结核病防治机构（18个）的所有在职工作人员（独立结核病防治机构调查对象为全体职工，非独立结核病防治机构调查对象为从事结核病诊治、检查、督导、检验、护理等所有医务人员以及所属行政后勤人员）作为调查对象；对调查对象进行PPD皮试检查。结果2153人接受了PPD皮试检查，阳性率为60．6％，其中医务人员的阳性率为66．1％，根据市、地与县级工作人员数权重进行加权调整后全省结核病防治机构工作人员的PPD阳性率为57．3％，医务人员的阳性率为62．8％。经X^2检验，PPD皮试阳性率与强阳性率医务人员均显著高于非医务人员，市级工作人员均显著高于县级工作人员，30岁以上年龄组较高，不同BCG接种史、不同性别之间无显著差别。多因素分析前三者差异有统计学意义。结论河南省结核病防治机构内结核病感染控制工作较为薄弱，机构内工作人员尤其是医务工作人员工作环境结核病感染暴露危险较高。