Biomedical subjects

C C Leung

Publications and source records attributed to C C Leung.

At least 19 recordsLinked to original sources

PubMed2006

Smoking and tuberculosis among silicotic patients.

The aim of the present study was to investigate the relationship between smoking and tuberculosis (TB) among high-risk silicotic patients in Hong Kong. A cohort of 435 silicotic patients tuberculin tested from 1995-2002 was prospectively followed-up until the end of 2005. Baseline characteristics were analysed with respect to positive tuberculin reaction (> or =10 mm) at baseline and subsequent development of TB. Smoking, alcohol use and body mass index were independent predictors of positive tuberculin reaction at baseline in multiple logistic regression analysis. Total cigarette pack-yrs did not demonstrate any significant effect. The annual incidences of TB were 1,841, 2,294 and 4,181 per 100,000 for never-, ex- and current smokers, respectively. On Cox proportional hazard analysis, current smokers have a significantly higher risk of TB than other silicotic patients (adjusted hazard ratio (95% confidence interval (CI)): 1.96 (1.14-3.35)) after controlling for age, alcohol use, tuberculin status, treatment for latent TB infection and other relevant background/disease factors. A significant dose-response relationship was also observed with the daily number of cigarettes currently smoked. Smoking cessation may reduce 32.4% (95% CI: 6.5-54.0) of the risk. Smoking increases the risk of both tuberculosis infection and subsequent development of the disease among silicotic patients.

Age Factors↗

PubMed2006

Standard anti-tuberculosis treatment and hepatotoxicity: do dosing schedules matter?

A nested case-control study was conducted in order to examine whether dosing schedules of standard pyrazinamide-containing anti-tuberculosis (TB) treatment (standard treatment) might affect hepatotoxicity. The present authors retrospectively identified all patients with hepatitis using biochemical criteria from a cohort of 3,007 clinic patients who commenced anti-TB treatment from January 1 to June 30, 2001. Each case with hepatitis between 1-9 weeks post-TB treatment was compared using conditional logistic regression analysis with two controls selected randomly from patients without hepatitis in the same period and matched by sex, age and standard treatment. Impacts of sex and age were examined by logistic regression analysis of cases and patients without hepatitis. Hepatitis occurred in 167 patients, of whom 96 qualified as cases. A conditional logistic risk model identified hepatitis B surface antigen carriage as the only risk factor (odds ratio (95% confidence interval (CI)) 1.8 (1.1-3.1)). Logistic regression analysis showed that sex was nonsignificant but ageing increased the odds of hepatitis. The risk of hepatitis increased from 2.6% (1.9-3.5%) to 4.1% (3.2-5.3%) as age exceeded 49 yrs. Dosing schedules in the first 9 weeks have little impact on hepatotoxicity. If patients at risk of both hepatitis and relapse receive standard treatment, daily dosing is preferable.

Adult↗

PubMed2006

Mortality from non-malignant respiratory diseases among people with silicosis in Hong Kong: exposure-response analyses for exposure to silica dust.

OBJECTIVES: To examine the exposure-response relationships between various indices of exposure to silica dust and the mortality from non-malignant respiratory diseases (NMRDs) or chronic obstructive pulmonary diseases (COPDs) among a cohort of workers with silicosis in Hong Kong. METHODS: The concentrations of respirable silica dust were assigned to each industry and job task according to historical industrial hygiene measurements documented previously in Hong Kong. Exposure indices included cumulative dust exposure (CDE) and mean dust concentration (MDC). Penalised smoothing spline models were used as a preliminary step to detect outliers and guide further analyses. Multiple Cox's proportional hazard models were used to estimate the dust effects on the risk of mortality from NMRDs or COPDs after truncating the highest exposures. RESULTS: 371 of the 853 (43.49%) deaths occurring among 2789 workers with silicosis during 1981-99 were from NMRDs, and 101 (27.22%) NMRDs were COPDs. Multiple Cox's proportional hazard models showed that CDE (p = 0.009) and MDC (p<0.001) were significantly associated only with NMRD mortality. Subgroup analysis showed that deaths from NMRDs (p<0.01) and COPDs (p<0.05) were significantly associated with both CDE and MDC among underground caisson workers and among those ever employed in other occupations with high exposure to silica dust. No exposure-response relationship was observed for surface construction workers with low exposures. A clear upward trend for both NMRDs and COPDs mortality was found with increasing severity of radiological silicosis. CONCLUSION: This study documented an exposure-response relationship between exposure to silica dust and the risk of death from NMRDs or COPDs among workers with silicosis, except for surface construction workers with low exposures. The risk of mortality from NMRDs increased significantly with the progression of International Labor Organization categories, independent of dust effects.

Adult↗

PubMed2006

Prevalence and determinants of positive tuberculin reactions of residents in old age homes in Hong Kong.

OBJECTIVE: To determine the prevalence of tuberculous infection and the predictors of positive tuberculin reactivity in old age home residents in Hong Kong. DESIGN: Cross-sectional study. METHODS: A questionnaire-interview and review of medical records were carried out, together with measurement of weight and height/arm span and assessment of nutritional status. A one-stage tuberculin skin test (TST) was performed using two units of PPD RT23. An induration > or = 10 mm was considered as positive. RESULTS: Of 3682 residents (71.7% participation, mean age 82 years) who agreed to undergo a TST, 46.3% had a positive reaction. Factors associated with a significantly higher risk of a positive TST included being male, an ex- or current smoker and having a past history of tuberculosis (TB). Factors associated with reduced positive tuberculin reactivity included older age groups (> 70 years), a history of cancer and chronic obstructive pulmonary disease and low body mass index quartiles. CONCLUSION: In old age homes, the high prevalence of latent tuberculous infection is responsible for the high rate of active TB due to reactivation. Early diagnosis and treatment are necessary to prevent transmission of disease in these crowded environments with susceptible individuals.

Age Factors↗

PubMed2006

Occupational tuberculosis: a review of the literature and the local situation.

OBJECTIVE: To review the risks and control of occupation-related tuberculosis. DATA SOURCES: Statutory notification data, local tuberculosis programme data, and census data were reviewed. Literature search of PubMed was performed up to December 2005. STUDY SELECTION: Original and major review articles related to tuberculosis among health care workers and guidelines for prevention were reviewed. DATA EXTRACTION: Relevant data were extracted from our literature review and local sources. DATA SYNTHESIS: Earlier experimental data demonstrated an airborne spread of tuberculosis and a steady state mathematical model for quantification of the transmission risk. In the post-chemotherapy era in developed countries, few studies demonstrated an occupational risk of tuberculin conversion outside of outbreak settings, and few studies were able to conclusively demonstrate an increased risk of active tuberculosis among health care workers. In countries with limited resource, the situation may be different, with a higher tuberculosis incidence among health care workers. Local tuberculosis programme and notification data from the Labour Department did not show an increased risk of active tuberculosis among health care workers. Although administrative control, engineering control, and personal protection are widely accepted control measures, it is difficult to quantify their cost-effectiveness. CONCLUSIONS: Although an increased liability to tuberculosis among health care workers is expected due to the concentration of infectious patients in their environment, prompt diagnosis and initiation of treatment may minimise the risk. A high background rate of disease and possible healthy worker effect may make it difficult to pick up a small risk differential. With the ongoing threat of a nosocomial outbreak, continuing vigilance is called for.

BCG Vaccine↗

PubMed2005

Removal of batteries from solid waste using trommel separation.

This paper describes the design and testing of a trommel for separation of batteries from solid waste. A trommel is a cylindrical separation device that rotates and performs size separation. It has also been used in areas such as municipal solid waste (MSW) processing, classifying construction and demolition debris, screening mass-burn incinerator ash and compost processing. A trommel has been designed based on size separation to separate household batteries from solid waste, which can then be used as feedstock for alternative applications of solid waste combustion, particularly where the metal content of the product is also a critical parameter, such as the Co-Co process for integrated cement and power production. This trommel has been tested with batches of university office and restaurant wastes against various factors. The recovery efficiency of batteries increases with decreasing inclination angle of the trommel and decreasing rotational speed. A physical characterization of the university solid waste has been performed with a 20-kg sample of the tested waste. It was found that there is a trend of decreasing recovery of batteries with increasing paper composition, and a trend of increasing recovery of batteries with increasing organic materials composition.

Manufactured Materials↗

PubMed2005

Tuberculin response in BCG vaccinated schoolchildren and the estimation of annual risk of infection in Hong Kong.

BACKGROUND: In Hong Kong there has been nearly universal neonatal BCG vaccination coverage since 1980. METHOD: 21 113 schoolchildren aged 6-9 years were skin tested with one unit of tuberculin (PPD RT-23) using the intradermal technique during a routine BCG revaccination programme. Information on sex, date of birth, date of tuberculin testing, and tuberculin reaction size at 72 hours was retrieved. The annual risk of tuberculous infection (ARTI) was estimated by three different approaches. RESULTS: Significantly higher tuberculin positive rates were found in girls and with increasing age at all commonly used cut-off points (5, 10, and 15 mm). Using a cut-off point of > or =10 mm and the formula 1- (1 - tuberculin positive rate)(1/age), the ARTI was estimated to be 1.93% (95% CI 1.84 to 2.03) for girls and 1.41% (95% CI 1.33 to 1.50) for boys. Using the differences in the tuberculin positive rate between the 6-7 year and 8-9 year age groups, the ARTI became 1.90% (95% CI 1.09 to 2.70) and 1.84% (95% CI 1.15 to 2.54) for girls and boys, respectively. When the prevalence of infection was estimated by locating a secondary peak of the tuberculin reaction distribution curve at 15 mm and assuming a symmetrical distribution of reaction sizes among those infected around this peak, the corresponding ARTI was much lower at 0.52% (95% CI 0.46 to 0.59) and 0.43% (95% CI 0.37 to 0.49) for girls and boys, similar to that estimated indirectly from the prevalence of disease. CONCLUSION: The ARTI as estimated by conventional methods was unexpectedly high among BCG vaccinated children and did not agree with that anticipated from the annual incidence of active disease. Further studies are needed to address the discrepancies, including the possible interaction between BCG and other environmental stimuli.

Age Factors↗

PubMed2005

Directly observed treatment of tuberculosis in Hong Kong.

OBJECTIVE: To evaluate the local use of out-patient directly observed treatment (DOT) for tuberculosis (TB) control. SETTING: Seventeen government chest clinics managing around 80% of TB patients in Hong Kong. METHOD: A retrospective cohort. TB patients registered for treatment from 1 July to 31 August 2000 were followed up for 2 years. Baseline socio-demographic and clinical characteristics were correlated with adherence to DOT, mode of treatment and treatment outcomes. RESULTS: Of 988 patients, respectively 142, 140 and 21 switched to non-DOT within 2 months, 2-6 months and after 6 months. More Chinese patients than ethnic minorities switched to non-DOT within the first 2 months (15.2% vs. 0%, P = 0.001). Geographical inconvenience (31.7%) was the primary reason for switching initially, with increasing proportions giving no specific reason after the second month. Patients staying on DOT in the first 2 months had a significantly higher cure rate than those not on DOT, in both univariate (92.7% vs. 83.9%, P = 0.002) and multivariate analysis (OR = 2.5, P = 0.001). Subsequent switching, intermittent or daily regimen did not appear to affect the outcome. CONCLUSION: Significant numbers of patients failed to stay on DOT, and those staying initially had a better outcome.

Aged↗

PubMed2005

Chest radiograph screening for tuberculosis in a Hong Kong prison.

SETTING: Long-stay prisoners are not regularly screened for TB in Hong Kong. OBJECTIVE: To evaluate tuberculosis (TB) screening in prison. METHOD: All prisoners in a maximum security prison as of 31 October 2001 were screened by chest radiograph (CXR), except for those being followed up for TB or examined by CXR in the last 6 months. RESULTS: A total of 814 male prisoners aged 34.6 +/- 9.6 (mean +/- SD) years were successfully screened. Of 53 cases (6.51%) with radiographic abnormalities, 10 active TB cases (8 culture-negative, 2 culture-positive) were diagnosed, giving an overall yield of 1.23% (95%CI 0.59-2.26). There was no statistical difference in age, ethnicity, place of birth or residency status between those with and those without TB (all P > 0.05). Incarceration > or = 2 years, being in current prison > or = 2 years and not having CXR in last 2 years were associated with TB in univariate analysis (all P < 0.05), but only the last remained an independent predictor in multiple logistic regression (OR 16.8, 95%CI 2.1-132.9, P = 0.008). In that group, the yield was 3.1% (95%CI 1.42-5.89). No further cases were detected in the subsequent 2 years. CONCLUSION: CXR screening of long-stay prisoners gave a high yield in this study.

Adult↗

PubMed2005

Socio-demographic and geographic indicators and distribution of tuberculosis in Hong Kong: a spatial analysis.

OBJECTIVE: To determine the socio-demographic and geographic indicators responsible for the distribution and transmission of tuberculosis (TB) in Hong Kong using geographical information system (GIS) technology. MATERIALS AND METHODS: All patients with bacteriologically proven TB over a period of 3 years (May 1999-April 2002) residing within Hong Kong Island were studied. Molecular characterisation of their sputum isolates by IS6110-based restriction fragment length polymorphism (RFLP) technique was performed. Socio-demographic data were derived from the 2001 Hong Kong population census. Geographic coordinates of patients' addresses were linked to the GIS; large street block groups (LSBGs) were the units of analysis. RESULTS: Of 2387 patients with bacteriologically confirmed TB, 2332 had valid addresses distributed in 430 LSBGs in Hong Kong Island. Of the five socio-demographic indicators studied, significant correlations were found between the rate of TB in an LSBG and low educational attainment, elderly population and low-income household, but not population density or unemployment. The five socio-demographic indicators were not different between LSBG with clustered cases and those with unique cases. CONCLUSION: Low educational attainment, old age and poverty were significant determinants of the rate of TB in different parts of Hong Kong, while none of the socio-demographic indicators was related to disease transmission.

Aged↗

PubMed2004

Direct detection of rifampin-resistant mycobacterium tuberculosis in respiratory specimens by PCR-DNA sequencing.

This study evaluated the feasibility of a molecular strategy based on identification of Mycobacterium tuberculosis by IS6110 PCR or Cobas Amplicor PCR, and rpoB PCR-DNA sequencing of the 81-bp rifampin resistance determining region (RRDR) for direct detection of rifampin resistance in respiratory specimens. A collection of 2,138 respiratory specimens and 352 nonduplicate M. tuberculosis isolates (including 233 isolates from the evaluated respiratory specimens and an additional collection of 119 stored isolates) from Southern China was investigated. Using culture as the reference test, the overall diagnostic sensitivities of an acid-fast bacillus (AFB) smear, Cobas Amplicor PCR, IS6110 PCR were 54.5% (156 of 286), 86.7% (248 of 286), and 89.2% (255 of 286), respectively. The sensitivities of the rpoB PCR for the specimens with positive AFB smears and with positive PCR results in the IS6110 PCR and/or Cobas Amplicor PCR were 100% (156 of 156) and 92.3% (239 of 259), respectively. Of the 352 nonduplicate M. tuberculosis isolates, the agar proportion method for rifampin reported 39 resistant strains. Full agreement (352 of 352) was found with the agar proportion method and the genotype inferred from the rpoB DNA sequencing data for rifampin. Thirty-nine mutations of nine distinct kinds, eight point mutations, and one deletion within the RRDR were found in the 39 resistant strains. For the direct DNA sequencing performed on rpoB PCR-positive respiratory specimens, the concordance with the agar proportion method and the subsequent PCR-sequencing for the culture isolate was 100%. This strategy has potential application for direct and rapid diagnosis of rifampin-resistant M. tuberculosis in IS6110 PCR or Cobas Amplicor PCR-positive respiratory specimens.

Antibiotics, Antitubercular↗

PubMed2004

Socio-economic factors and tuberculosis: a district-based ecological analysis in Hong Kong.

BACKGROUND: Relatively little is known about the impact of socio-economic factors on tuberculosis in a metropolitan city with high disease incidence. METHOD: District-specific tuberculosis notification rates for 1995--1997 and 2000--2002 were indirectly sex- and age-adjusted and compared with the socio-economic characteristics in the 1996 by-census and 2001 census. RESULTS: The differences between the 18 districts persisted after 3-year averaging and indirect standardisation. Only the percentage of population born locally, the percentage of the population widowed or divorced and the percentage of households residing in rooms or bedsits were consistently associated with the standardised notification ratios (SNR) for both periods, the first being negatively so (all P < 0.05). In a combined analysis with a general linear model for both periods, birth in China, residence <7 years, speaking other Asian languages, being married and in a single household were also significantly associated with the SNR (all P < 0.05). Using a backward conditional approach, only local birth, being married, and residing in rooms or bedsits were independent predictors of SNR (all P < 0.05). There was no significant association between SNR and socio-economic indices on education, occupation, unemployment and income. CONCLUSION: Socio-economic factors other than simple poverty are affecting the district-specific tuberculosis rates in Hong Kong.

Female↗

PubMed2004

Risk factors for defaulting from anti-tuberculosis treatment under directly observed treatment in Hong Kong.

OBJECTIVE: To identify risk factors for defaulting from anti-tuberculosis treatment. SETTING: Directly observed treatment in Hong Kong Government chest clinics. DESIGN: Defaulters were recruited from a cohort of tuberculosis patients registered from 1 January to 31 March 1999. Three controls per case, matched for age and sex, were selected randomly from the cohort. Patient factors, initial tuberculosis characteristics and treatment-related variables were collected by review of medical records. RESULTS: On matching 102 defaulters and 306 controls, a logistic risk model of default that considered patient factors, initial disease characteristics and treatment-related factors identified seven risk factors: current smoking (OR 3.00, 95% CI 1.41-6.39), past TB with default (OR 6.23, 95% CI 1.95-19.91), poor initial adherence (OR 117.21, 95% CI 13.52-1015.92), fair initial adherence (OR 11.02, 95% CI 2.15-56.43), unknown initial adherence (OR 6.59, 95% CI 3.47-12.49), treatment side effects (OR 13.30, 95% CI 3.23-54.79), and subsequent hospitalisation (OR 0.27, 95% CI 0.11-0.67). Its predictive power was 85%. Another model that considered only factors on registration for treatment gave a lower predictive power of 70%. CONCLUSIONS: Treatment default could be predicted fairly accurately by considering patient and treatment-related factors.

Antitubercular Agents↗

PubMed2003

Tuberculosis in Hong Kong-patient characteristics and treatment outcome.

OBJECTIVES: To identify the general characteristics of patients with tuberculosis, and to evaluate their treatment outcomes. DESIGN: Retrospective study. SETTING: Tuberculosis and Chest Service, Department of Health, Hong Kong. SUBJECTS AND METHODS: All patients with tuberculosis registered for treatment from 1 January 1996 to 31 December 1996 were included in the study. Information was extracted from their medical records at treatment commencement and at 12 and 24 months after treatment was instigated. Data gathered included demographic data, past treatment, site of disease, case category, treatment regimen, bacteriological status, and treatment outcome. RESULTS: There were 5757 patients for analysis. Approximately one third of patients were aged 60 years or older, and 69.1% were male. Pulmonary disease alone occurred in 77.7% of patients, while both pulmonary and extrapulmonary diseases occurred in 8.6%. New patients comprised 84.6% of cases, and 16.3% had concomitant illnesses. There was excess risk of disease among patients who were male, elderly, or who had silicosis. Only 0.1% of patients were co-infected with human immunodeficiency virus infection. Among the 5757 cases evaluated, 1324 (23.0%) were new patients with a positive sputum smear, 299 (5.2%) were patients who were retreated with a positive sputum smear, and 4134 (71.8%) were new or retreatment patients with a negative sputum smear. The overall treatment completion rates at 12 and 24 months were 80.4% and 84.8%, respectively. Males and patients aged 60 years or older had lower treatment completion rates. Non-adherence, transfer to other services, and mortality among the elderly were key factors influencing treatment outcomes. Co-morbidity was associated with better case-holding, and this more than compensated for its effect on prolongation of treatment and mortality. CONCLUSIONS: There was an excess risk of tuberculosis among male and elderly patients, who also had a less favourable outcome. Active screening of clearly identified risk groups may be appropriate but requires the completion of more in-depth studies and careful cost-effectiveness analyses. Further efforts with respect to case-holding are indicated to address treatment defaulting and transfer rates.

Adolescent↗

PubMed2003

Prevalence and predictors of default from tuberculosis treatment in Hong Kong.

OBJECTIVE: To determine the prevalence and risk factors of default from tuberculosis treatment in Hong Kong. DESIGN: Retrospective study. SETTING: Data were obtained from programme forms completed by physicians in the Hong Kong Government Tuberculosis and Chest Service and from medical records from Hong Kong chest clinics. PATIENTS: In all, 5917 patients registered for antituberculous drug therapy in 1996; medical records of 5757 patients were reviewed. MAIN OUTCOME MEASURES: Patients who defaulted treatment were defined as those who had failed to collect medication for more than 2 consecutive months after the date of the last attendance during the course of treatment. Demographic and clinical characteristics, including history, treatment, and outcome, were compared between defaulters and non-defaulters, both among the whole group and among those with pulmonary disease. RESULTS: There were 442 (8%) patients who defaulted from treatment. Forty-five percent of those who defaulted did so in the first 2 months of treatment. Key risk factors associated with non-compliance were a history of default, male sex, and a history of concomitant liver disease or lung cancer. Among patients with pulmonary tuberculosis (381 defaulters and 1537 non-defaulters), multiple drug resistance was also associated with default from treatment. Among defaulters with pulmonary disease, 39% were still bacteriologically positive at the time of default. CONCLUSION: Default from treatment may be partially responsible for the persistent high rates of tuberculosis in Hong Kong in the past decade. Health professionals should ensure that all barriers to treatment be removed and that incentives be used to encourage treatment compliance.

Antitubercular Agents↗

PubMed2003

Smoking and tuberculosis in Hong Kong.

OBJECTIVE: To study the relationship between smoking and tuberculosis in Hong Kong. METHOD: Indirect sex and age adjustment was used to compare the prevalence of ever smokers between a sample of 851 patients from the 1996 tuberculosis notification registry and the general population. The clinical characteristics of smokers and non-smokers were compared by stratified univariate analysis and multiple logistic regression. RESULTS: Tuberculosis patients were more likely to have smoked than population controls. The respective odds ratios for ever smoking between tuberculosis patients and population controls were 2.44 and 2.08 for males and females aged 16-64 (Mantel-Haenszel weighted OR = 2.40, P < 0.001), and 2.09 and 2.83 for males and females aged > or = 65 (Mantel-Haenszel weighted odds ratio = 2.19, P < 0.001). Male sex, age > or = 65, working at onset of illness, regular alcohol use, drug abuse and absence of contact history were associated with ever smokers (all P < 0.05). Ever smokers were more likely to have cough (OR 1.69), dyspnoea (OR 1.84), upper zone involvement (OR 1.67), cavity (OR 1.76), miliary lung involvement (OR 2.77), positive sputum culture (OR 1.43), but less isolated extrathoracic involvement (OR 0.31), even after controlling for the confounding background variables (all P < 0.05). CONCLUSION: There was a consistent association between smoking and tuberculosis. More aggressive lung involvement was also found among ever smokers.

Adolescent↗

PubMed2001

Tuberculosis risk factors in a silicotic cohort in Hong Kong.

SETTING: Hong Kong silicotic patients are followed regularly at the Pneumoconiosis Clinic. OBJECTIVE: To quantify the incidence of tuberculosis disease that occurs after the date of diagnosis of silicosis (DOD), and to identify the risk factors for its development. DESIGN: Retrospective analysis of a Hong Kong silicotic cohort with DOD from 1 January 1988 to 31 December 1993. RESULTS: Of 718 subjects whose records were identified, 11 were excluded from the study. The incidence of tuberculosis (TB) after DOD was 3019 patients per 100,000 population, approximately nine times that of the local population matched for age and sex. Twelve factors were subject to univariate analysis followed by logistic regression. Four TB risk factors were identified: 1) no anti-tuberculosis treatment before DOD (relative risk [RR] 4.51, 95% confidence interval [CI] 2.46-8.24), 2) progressive massive fibrosis (PMF) (RR 3.78, 95%CI 2.25-6.36), 3) small opacities exceeding 1.5 mm (RR 2.17, 95%CI 1.38-3.42), and 4) caisson work (RR 1.56, 95%CI 1.01-2.41). Relative risks were calculated for patient subgroups stratified according to TB risk factors. CONCLUSION: This study has reaffirmed the strong association of tuberculosis and silicosis, and has identified several TB risk factors with a logistic regression model.

Adult↗

PubMed2001

Efficacy of the BCG revaccination programme in a cohort given BCG vaccination at birth in Hong Kong.

SETTING: Revaccination of tuberculin-negative school-children is a regular practice in Hong Kong. OBJECTIVE: To assess the efficacy of BCG revaccination guided by tuberculin skin testing. METHOD: A cohort of 303,692 children vaccinated at birth was followed through the tuberculosis notification register for the development of active disease. The percentage of cohort who participated in the BCG revaccination program during primary school was estimated from the vaccination statistics of the Hong Kong Department of Health. The BCG revaccination history of identified cases was ascertained through vaccination cards and clinic records. RESULTS: A total of 85.2% of the cohort participated in the BCG revaccination programme; 79.7% of the participants were tuberculin-negative and revaccinated; 343 developed tuberculosis after the age of 11; 302 were among the participants in the programme while 41 were not. The tuberculosis incidence was 16.5 and 12.9 per 100,000 person-years for participants and non-participants, respectively (RR 1.28, 95%CI 0.92-1.77). Among the participants, tuberculosis incidence was 12.5 and 32.0/100,000 person-years, respectively, for the tuberculin-negative/BCG revaccinated group and the tuberculin-positive/non-revaccinated group (RR 0.39, 95%CI 0.31-0.49). CONCLUSION: This study failed to demonstrate any significant difference in the incidence rates of tuberculosis among participants and non-participants in a school BCG revaccination programme. The increased risk for tuberculosis in the tuberculin-positive group does not support the use of the tuberculin testing for detection of immunity conferred by neonatal BCG vaccination.

Adolescent↗