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.     

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.     

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.     

Investigation of the delayed type hypersensitivity reaction in atopic patients

INTRODUCTION: In the last decades the prevalence of atopic diseases has increased highly in developed countries. Although the reasons for this increase are not clear, it has been hypothesized that a reduction in infections and immunization programs may contribute to the increased prevalence of atopic diseases. AIM: In the present study the relationship between tuberculin response and atopic disease was investigated. METHODS: A total of 1012 children vaccinated with BCG were included in the study. All the children were given five tuberculin units PPD, and PPD indurations were recorded after 72 h. The test result was considered to be positive if the induration size was greater than 9 mm. The atopic anamnesis (atopic dermatitis, rhinitis, conjunctivitis, asthma, urticaria) in the children and their families were investigated using a questionnaire. RESULTS: 608 individual (60.1%) had positive and 404 (39.9%) had negative tuberculin test. Positive atopic personal anamnesis was found in 31.74% in children with positive tuberculin skin test, whereas 39.85% was found in children with negative tuberculin test (p < 0.009, Fischer-test). Similarly more positive family anamnesis for atopic diseases was found among children with negative tuberculin test. In children with negative tuberculin test the prevalence of allergic conjunctivitis and rhinitis was significantly higher as compared to the group with positive tuberculin test. CONCLUSIONS: The authors found an inverse correlation between tuberculin response and atopy status. The observed decreased tuberculin sensitivity in atopic individuals is, however, probably not the cause, but rather the consequence of the disturbed immune regulation in atopic diseases.     

Tuberculin reactivity among California Hispanic migrant farm workers

We conducted a cross-sectional study of tuberculin reactivity among residents of two northern California migrant-farm-worker housing centers. Participants completed a brief health questionnaire and were offered tuberculin skin testing with radiologic and medical follow-up. Four hundred and sixty-nine persons (estimated participation rate: 70%) completed questionnaires. All but one were Hispanic. Two hundred and ninety-six (63%) participants completed tuberculin skin testing and 49 (16.6%) showed reactivity (≥10 mm induration at 48–72 hours). Increased prevalence was seen for the 15–39-year age group (vs. persons younger than 15: OR 2.59; 95% CI 0.79–8.47), former smokers (vs. never smokers: OR 3.11; 95 %CI 1.20–8.09), and persons born outside the U.S. (OR 2.09; 95% CI 0.66–6.61). Prophylaxis with isoniazid was recommended for 23 persons; nine (39%) completed therapy. No cases of active tuberculosis were found. Prevalence of tuberculin reactivity in this population is lower than reported among Hispanic farm workers in the eastern and midwestern U.S. Higher prevalence may obtain among California farm workers not included in the study population, including homeless, single, and highly mobile persons. Public-health efforts in this population should focus on ever-smokers, young adults, and persons born outside the U.S. Am. J. Ind. Med. 32:600–605, 1997. © 1997 Wiley-Liss, Inc.     

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。     

Decreased cellular immune response in wasted but not in stunted children

BCG immunization was given to 114 rural Mexican children who had not responded with a positive reaction to a previous tuberculin test. A second tuberculin test was given to these children 5 weeks after the immunization. Heights, weights and upper-arm circumferences were also measured at these two time points. The diameter of induration resulting from the tuberculin test was measured. The percent of E rosette-forming lymphocytes and the mean number of sheep red blood cells (SRBC) per lymphocyte were also determined in 27 of these children. The diameter of the induration, the percent of rosette-forming lymphocytes and the mean number of SRBC per lymphocyte were positively associated with measures of wasting, but not with measures of stunting. We conclude that cell-mediated immunity is impaired in wasted, even when mild to moderate, but not in stunted children.     

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.     

Tuberculin skin test conversion among medical students at a teaching hospital in Rio de Janeiro, Brazil.

OBJECTIVE: To describe the cumulative incidence of and risk factors for tuberculosis (TB) infection among medical students. DESIGN: In 1999, a cohort study of medical students with negative results (induration < 10 mm) on tuberculin skin test (TST) was performed. Students who had undergone two-step testing in 1998 were retested. SETTINGS: University and teaching hospital and referral center for TB and acquired immunodeficiency syndrome, and the Health Sciences Building of the Medical School of the Federal University of Rio de Janeiro, Brazil. PARTICIPANTS: A sample of 618 consecutive medical students with negative TST results who had been tested 12 months before were approached. Information about sociodemographic characteristics, bacille Calmette-Guérin vaccination history, and potential exposures to TB was obtained using a standardized questionnaire. Four hundred fourteen (67%) students completed the study. Students were at two different levels of their training programs (juniors = no contact with patients; seniors = intensive contact with patients). RESULTS: Of 414 participants, 16 (3.9%; 95% confidence interval, 1.06% to 12.1%) had converted to a positive reaction after 1 year. In a multivariate logistic regression analysis, higher level of clinical training was confirmed to be an independent factor associated with TST conversion (odds ratio, 4.77; 95% confidence interval, 1.01 to 22.46; P= .048). CONCLUSION: Senior medical students are at increased risk of Mycobacterium tuberculosis infection in this setting. Therefore, a program of routine tuberculin skin testing and specific TB infection control guidelines are needed for this population.     

Development of a Vietnamese version of the Short form-36 Health Survey

We aimed to test the psychometric properties of a culturally relevant translation of the medical outcomes study short form-36 health survey (SF-36) with prospective Vietnamese migrants. The translated survey was interviewer-administered to 1610 Vietnamese aged over 15 years who had applied to migrate to Australia. All but two SF-36 items had good discriminant validity, and all eight scales of the Vietnamese version of the SFS-36 had good discriminant validity, which supports the use of SF-36 constructs to assess self-reported health status among Vietnamese migrants. However, the mental health, vitality and bodily pain scales demonstrated low internal consistency. This finding is likely to be a product of the increased diversity among scale items following modifications to improve cultural relevance. Further modifications to improve the internal consistency of these scales are required.     

Characteristics of injection drug users who utilize tuberculosis services at sites of the baltimore city needle exchange program

Objective To describe characteristics of needle-exchange program (NEP) participants who utilized tuberculosis services from an NEP site. Methods Between June 1998 and May 1999, tuberculosis services were advertised and offered to Baltimore, Maryland, NEP participants. Demographic and tuberculosis-specific data were collected on participants who self-selected into services. Analyses were based on being tuberculin skin tested, returning for a skin test reading, and testing tuberculin positive. Results Among 691 contacts with NEP participants, this service performed 296 tuberculin tests, with an 84% return rate for skin test reading. Participants were 32% female, 87% African American, and 11% employed. Higher frequency of NEP visits was positively associated with requesting tuberculosis services and returning for skin test reading. Among those who returned for skin test reading, longer smoking duration and problems getting food in the past year due to a lack of money were associated with a positive test. Conclusions Utilization of a tuberculosis service and high return rates can be achieved among NEP participants without formal recruitment strategies. Frequent exchange appears to facilitate return visits for NEP-based tuberculosis screening, which may imply accessibility for frequent exchangers. More extensive health services at sites of the Baltimore NEP appear to be warranted, with particular attention paid to effectiveness for frequent exchangers.     

THE RELATION of tuberculin sensitivity to pulmonary calcifications as an index of tuberculosis infection

A single intradermal tuberculin test of 10 TU was arbitrarily selected for use in the Danish mass antituberculosis campaign of 1950-52. The present report discusses how efficiently this test can distinguish tuberculosis-infected and uninfected members of the adult population; it is based on the relation between size of tuberculin reaction and frequency of intrathoracic (presumably tuberculous) calcifications in 50,000 adults.Frequency distributions by size of 10 TU reactions for the study population, divided into 10-year age-groups, show a very consistent pattern for all age-groups: a smooth bimodal curve with a zone of low frequency around the 6 mm point of induration clearly separating persons with large reactions from those with very small or no reactions.In persons 15-34 years old the frequency of pulmonary calcifications is very low for those with tuberculin reactions measuring 0-7 mm of induration; for those with reactions of 8-9 mm the frequency rises sharply and reaches a maximum for those with reactions 18 mm or larger. In the age-groups up to 54 years the frequency of calcifications remains very low in persons with no reactions to the tuberculin test; the sudden steep rise in frequency is displaced with age from right to left on the tuberculin-reaction scale, and there is a progressive increase in the frequency of calcifications with the increase in reaction size. In the age-group 55 years or more persons with no reaction also have a high frequency of calcifications, and there is only a very slight rise in the frequency from 0-1 mm to the largest reactions.Up to the age of about 50 years, probably few persons not reacting to the 10 TU test are tuberculosis-infected. For persons over this age, however, division of the population into two groups according to the tuberculin-reaction size apparently does not correspond to a division into infected and uninfected.     

Screening for tuberculosis among 2381 household contacts of sputum-smear-positive cases in The Gambia

Contact investigation is a key component of tuberculosis (TB) control in developed, but not developing, countries. We aimed to measure the prevalence of TB among household contacts of sputum-smear-positive TB cases in The Gambia and to assess the sensitivity of an enzyme-linked immunospot (ELISPOT) assay in this regard. Household contacts of adult smear-positive TB patients were assessed by questionnaire, purified protein derivative (PPD) skin test, ELISPOT assay, physical examination, chest X-ray and sputum/gastric aspirate. Thirty-three TB cases were identified from 2174 of 2381 contacts of 317 adult smear-positive pulmonary TB patients, giving a prevalence of 1518/100000. The cases identified tended to have milder disease than those passively detected. The sensitivity of ESAT-6/CFP-10 ELISPOT test as a screening test for TB disease was estimated as 71%. Fifty-six per cent of contacts with a PPD skin test result >or=10mm induration had detectable responses to ESAT-6/CFP-10 by ELISPOT; 11% with a negative PPD skin test (<10mm) had a positive ESAT-6/CFP-10 response. Active screening for TB among contacts of TB patients may have a role in TB control in The Gambia. These individuals are a high-risk group, and the disease identified is less advanced than that found through passive case detection. An ELISPOT assay was relatively insensitive as a screening test for TB.     

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。     

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.     

BCG vaccination among West African infants is associated with less anergy to tuberculin and diphtheria-tetanus antigens.

To examine risk factors for anergy, delayed-type hypersensitivity was assessed among 884 infants participating in a vaccine trial in Guinea-Bissau. The infants were skin-tested at 7.5 months of age with a panel of seven intradermal antigens. Risk factors for anergy to tuberculin or anergy to both the diphtheria and tetanus antigens were determined in relation to Bacillus Calmette-Guérin (BCG) vaccination, diphtheria-tetanus-pertussis (DTP) vaccination, and measles vaccination. We found sick children to be more anergic to tuberculin and diphtheria-tetanus antigens than healthy children (OR=2.49 (95% confidence interval 1.40-4.55)). There was a higher prevalence of anergy to tuberculin in the rainy season than in the dry season (OR=1.67 (1.25-2.23)). Children who had taken antimalarials within the last week had a higher prevalence of anergy to tuberculin (OR=1.41 (1.02-1.92)). BCG vaccination was significantly associated with less anergy to tuberculin and diphtheria-tetanus antigens (OR=0.42 (0.28-0.63), OR=0.77 (0.60-0.99), respectively). Children vaccinated with BCG before 1 month of age were more anergic to tuberculin than children vaccinated after 1 month (OR=1.61 (1.19-2.19)). DTP vaccination was associated with less anergy to diphtheria-tetanus antigens (OR=0.40 (0.32-0.49)), but not to tuberculin. Children with a positive reaction to tuberculin were less likely to be anergic to diphtheria-tetanus antigens (OR=0.36 (0.26-0.49)) than children with a negative tuberculin reaction. Children who were vaccinated with BCG before they received their last DTP vaccine were less anergic to diphtheria-tetanus antigens (OR=0.40 (0.16-0.88)) than other DTP-vaccinated children. In conclusion, current disease, rainy season, age below 1 month of age at the time of BCG vaccination, and administration of chloroquine or quinimax within the last 7 days were risk factors for anergy to tuberculin among 7.5-month-old infants. BCG vaccination and a positive tuberculin reaction were associated with a lower prevalence of anergy to both tuberculin and diphtheria-tetanus. Thus, BCG vaccination may contribute to better cell-mediated immune responses among infants.     

Tuberculosis risk among migrant farm workers on the Delmarva peninsula.

A survey was conducted to ascertain the risk of tuberculosis (TB) among migrant farm workers on the Delmarva peninsula. Relevant histories were obtained from 842 migrants; a total of 709 skin tests were completed, and 239 sputum specimens were examined for acid-fast bacilli (AFB) and culture. No cases of infectious tuberculosis were ascertained by history or AFB examination. One sputum culture was positive for M. tuberculosis and 13 were positive for various species of nontuberculous mycobacteria. Thirty-seven per cent of migrants tested had significant skin test reactions of 10 mm or more. Reaction rates for men were 41 per cent and for women 25 per cent. Age specific rates ranged from 14 per cent in children aged 5-14 to 54 per cent for ages 45-54. Rates for the principal national/ethnic groups were Haitians 55 per cent, Mexicans 36 per cent, US Blacks 29 per cent and US-born Latinos 20 per cent. Based on these results and other information currently available, it is recommended that current Centers for Disease Control (CDC) recommendations for TB prophylaxis continue to be applied for migrant workers, but that mass screening by skin testing in camp populations not be emphasized. Other recommendations focus on: case finding of active disease, improving continuity and follow-up, increasing coordination among involved agencies, and actively supporting improved economic and living conditions for migrant farm workers.     

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.     

Tuberculin reactivity among ninth-grade schoolchildren in the city of Havana, Cuba]

OBJECTIVE: To determine the proportion of 14-year-old schoolchildren in the city of Havana, Cuba, with a positive tuberculin skin test, as an indicator of the prevalence of tuberculosis infection among them. METHODS: Using single-stage cluster sampling, 1 936 Mantoux (tuberculin) tests were carried out with ninth-grade students (cohort born in 1985) during the 1999- 2000 school year in 20 basic high schools randomly selected in Havana. The tests were performed according to the standard technique recommended by the World Health Organization, and they were read after 72 hours. The percentage of skin tests that were positive and the average diameter of the indurations were calculated for the cohort overall and for the two genders. The means and the percentages were compared using the chi-square test, with 95% confidence intervals. The computer software used was Epi Info version 6.0. RESULTS: Of the tests read, 96% of them were negative (0-4 mm), 2.5% were doubtful (5-9 mm), and 1.5% were positive (>/=10 mm). The percentage of reactivity was 0.1% when a cutoff value of 15 mm was used. The mean diameter of the indurations was 0.41 mm. No statistically significant difference was found between the genders. CONCLUSIONS: In this study the proportion of schoolchildren with tuberculin reactivity, using an induration-diameter cutoff point of 10 mm, was very low (1.5%), and it was much lower (0.1%) when a cutoff point of 15 mm was used. The skin reactions with an induration diameter of >/=10 mm could be the expression of a natural infection if one takes into account the low frequency of bacillary tuberculosis in Cuba and that there is an inverse relationship between the time elapsed from the BCG vaccination and the intensity of the response to tuberculin. Therefore, that would mean that in this case (l)the point (.)prevalence of tuberculosis infection in this group of schoolchildren wou d be 1.5% ResumenObjetivos. Determinar la proporción de personas que reaccionan a la tuberculina como indicador de la prevalencia de infección tuberculosa en escolares de 14 a?os de Ciudad de La Habana, Cuba. Métodos. Mediante un muestreo monoetápico por conglomerados se aplicaron 1 936 pruebas de Mantoux (tuberculina) a estudiantes de noveno grado del curso escolar 1999-2000 (cohorte de los nacidos en 1985) de 20 escuelas secundarias básicas seleccionadas aleatoriamente en Ciudad de La Habana, Cuba. Las pruebas se realizaron según la técnica estándar recomendada por la Organización Mundial de la Salud y se evaluaron a las 72 horas. Se calcularon los porcentajes de reactividad y el diámetro medio de las induraciones cutáneas en la cohorte y según el sexo. Las comparaciones de medias y porcentajes se realizaron mediante la prueba de ji al cuadrado con 95% de confiabilidad. Se usó el programa Epi Info v. 6.0. Resultados. Noventa y seis por ciento de las pruebas leídas fueron negativas (0-4 mm), 2,5% fueron dudosas (5-9 mm) y 1,5% resultaron positivas ( >/= 10 mm). El porcentaje de reactividad disminuyó a 0,1% cuando se utilizó un valor de corte de 15 mm. El diámetro medio de las induraciones fue de 0,41 mm y no se detectó ninguna diferencia estadísticamente significativa en función del sexo. Conclusiones. La proporción de personas que reaccionaron a la tuberculina, usando como punto de corte un diámetro de induración cutánea de 10 mm, fue muy baja (1,5%) en este estudio y mucho más baja (0,1%) cuando se utilizó 15 mm como punto de corte. Si se toma en cuenta la baja frecuencia de tuberculosis bacilífera en Cuba y que hay una relación inversa entre el tiempo transcurrido desde la aplicación de la vacuna a base del bacilo de Calmette-Guérin (BCG) y la intensidad de la respuesta a la tuberculina, las reacciones cutáneas con un diámetro de induración >/= 10 mm podrían ser la expresión de una infección natural, por lo que, en ese caso, la prevalencia puntual de infección tuberculosa en este grupo de escolares sería de 1,5%.     

Migration and smoking: an epidemiological study of Finnish twins in Sweden

BACKGROUND: Male migrants from Finland to Sweden have been found to have a reduced risk of coronary heart disease after several years in Sweden. Changes in smoking habits may contribute to this reduced risk. AIMS: A study was undertaken to compare smoking habits in Finnish migrants to Sweden and subjects always living in Finland and to analyse whether the migration may have influenced smoking. METHODS: The study population consisted of same-sex twin pairs born in Finland younger than 76 years with at least one twin that had migrated to Sweden (n = 1,083 pairs). Smoking habits obtained by mailed questionnaire were compared in migration-discordant twin pairs to take into account early childhood and genetic factors. RESULTS: Immigrants and returnees with a history of smoking had predominantly started to smoke before the migration. Among women, immigrants to Sweden smoked more than never migrants in Finland, odds ratio (OR) 2.1 for current smokers (95% confidence interval CI 1.4-3.3) but this difference was already present before migration. In men there were essentially no differences in smoking prevalence between immigrants and never migrants but heavy smoking was less common among immigrants than among never migrant smokers, OR 0.5 (95% CI 0.2-0.9) and migration was associated with a greater propensity to cease smoking. CONCLUSIONS: Migration from Finland to Sweden does not seem to have had a strong influence on smoking among migrants. A favourable trend in smoking habits after migration may in part have contributed to reduced mortality and incidence of coronary heart disease in male Finnish migrants after several years in Sweden.