Patterns and characteristics of TB among key risk groups in Canada, 1993–2018

BACKGROUND: Canada has a low incidence of TB, although certain groups are disproportionately affected.OBJECTIVE: To describe and compare the epidemiology, trends and characteristics of TB in Quebec, Canada, among all patients reported during 1993–2018.METHODS: Demographics and risk factors were compared for the three groups accounting for most TB diagnoses reported in Quebec (foreign-born, Canadian-born non-Indigenous and Inuit). Average annual incidence and incidence rate ratios (IRRs) were estimated and compared using Poisson regression.RESULTS: Of 6,941 persons with a first episode of TB, 4,077 (59%) were foreign-born, 2,314 (33%) were Canadian-born non-Indigenous and 389 (6%) were Inuit. The average annual incidence for foreign-born, Canadian-born non-Indigenous and Inuit was respectively 17.0, 1.4 and 137.1 per 100,000 population. Compared to Canadian-born non-Indigenous, the IRR for foreign-born and Inuit was respectively 12.3 (95% CI 11.6–12.9) and 98.7 (95% CI 88.6–109.9). There was evidence of community transmission among the Inuit, with more than 80% of patients having a TB contact (2012–2018 data) and 65% (251/389) of diagnoses in those aged <25 years.CONCLUSION: Although TB rates among the Canadian-born non-Indigenous are extremely low, there are persistent and distinct TB epidemics among the foreign-born and Inuit. Tailored approaches to TB prevention and care are needed to address TB among high-risk populations in low TB incidence settings.

Investigation of the risk factors for tuberculosis: a case-control study in three countries in West Africa

BACKGROUND

Host-related and environment-related factors have been shown to play a role in the development of tuberculosis (TB), but few studies were carried out to identify their respective roles in resource-poor countries.

METHODS

A multicentre case-control study was conducted in Guinée, Guinea Bissau, and The Gambia, from January 1999 to March 2001. Cases were newly detected smear positive TB patients. Two controls were recruited for each case, one within the household of the case, and one in the community.

RESULTS

Regarding host-related factors, univariate analysis by conditional logistic regression of 687 matched pairs of cases and household controls showed that TB was associated with male sex, family history of TB, absence of a BCG scar, smoking, alcohol, anaemia, HIV infection, and history and treatment of worm infection. In a multivariable model based on 601 matched pairs, male sex, family history of TB, smoking, and HIV infection were independent risk factors of TB. The investigation of environmental factors based on the comparison of 816 cases/community control pairs showed that the risk of TB was associated with single marital status, family history of TB, adult crowding, and renting the house. In a final model assessing the combined effect of host and environmental factors, TB was associated with male sex, HIV infection, smoking (with a dose-effect relationship), history of asthma, family history of TB, marital status, adult crowding, and renting the house.

CONCLUSION

TB is a multifactorial disorder, in which environment interacts with host-related factors. This study provided useful information for the assessment of host and environmental factors of TB for the improvement of TB control activities in developing countries.

Yield of casual contact investigation by the hour

OBJECTIVE

Among casual contacts of tuberculosis (TB) patients, to assess how duration of contact, prior mycobacterial exposure, and performance of one or two tuberculin skin tests (TST), affect the likelihood that a positive TST represents conversion.

METHODS

Published estimates of mycobacterial prevalence and BCG coverage, and their effect on single or repeated TSTs, were used to calculate baseline prevalence of TST reactions in four populations commonly encountered in North American contact investigations. Using published estimates of hourly risk of TB infection, the probability that a positive TST represented conversion was calculated.

RESULTS

Among casual contacts with 20 hours of exposure, the likelihood that a single positive TST performed after 8 weeks represented conversion was 77% in persons from populations with low prior mycobacterial exposure, but only 6-8% in foreign-born populations. If tuberculin testing was performed immediately and then again 8 weeks post-exposure, 14-38% of all positive tests would be due to boosting, related to prior exposure to mycobacteria or BCG. If one TST, performed 8 weeks after exposure, was positive in casual contacts from populations with high prevalence of prior mycobacterial exposures, the likelihood of true conversion was less than 40%, even after 200 hours of exposure.

CONCLUSIONS

A single TST performed 8 weeks after the end of exposure among casual contacts will detect all true conversions, and minimize misdiagnosis due to boosting. The decision to perform TST on casual contacts should consider the likelihood of prior mycobacterial exposure in the population, as well as the duration of exposure.

Disseminated tuberculosis with and without a miliary pattern on chest radiograph: a clinical-pathologic-radiologic correlation

SETTING

Province of Manitoba, Canada.

OBJECTIVE

To describe the characteristics of disseminated tuberculosis (TBD) with and without a miliary pattern on chest radiograph, to determine the mortality, and to identify the demographic and clinical features associated with survival.

DESIGN

A retrospective case review.

RESULTS

Of 2013 cases of active tuberculosis reported to the Provincial Tuberculosis Registry between January 1979 and December 1993, 56 had disseminated disease. The odds of developing TBD were significantly higher in females. Compared to those with a miliary pattern (n = 42), those without a miliary pattern on chest radiograph (n = 14) were significantly more likely to have a risk factor for tuberculosis (86% vs 52%, P < 0.05) and to die (86% vs 21%, P < 0.001). The diagnosis of TBD was significantly more likely to be made at postmortem in non-miliary compared to miliary patients (43% vs 5%, P < 0.05). Amongst patients with a miliary pattern, the presence of one or more risk factors for tuberculosis was associated with a significantly higher mortality (P < 0.05). Meningitis was very uncommon and did not determine the outcome.

CONCLUSION

Disseminated tuberculosis patients without a miliary pattern on chest radiograph have an extremely high mortality rate; those with a miliary pattern may also succumb, especially if co-morbid with a condition known to increase the risk of tuberculosis.

Disseminated infection after intravesical BCG immunotherapy. Detection of organisms in pulmonary tissue

A 57-year-old man undergoing intravesical immunotherapy with BCG for transitional cell bladder carcinoma presented with dyspnea, fever, hypoxemia, and a diffuse micronodular pattern on chest radiograph. Transbronchial biopsy specimen revealed widespread noncaseating granulomas, and acid-fast bacilli were identified in sputum as well as in the biopsy tissue. The patient's condition responded promptly to antituberculous antibiotics given in conjunction with corticosteroids. Although no growth was evident on TB culture of the specimens, the presence of organisms indicates a probable infectious cause of the pulmonary disease process.

The prevalence of gallstone disease in very old institutionalized persons

We present the results of a study that was undertaken at a large geriatric nursing home to assess the prevalence of gallstone disease in very old institutionalized persons. One hundred seventeen residents underwent ultrasound examination of the gallbladder. Two thirds of 82 women and half of 35 men had gallstone disease. When stratified for age, 80% of women and men over the age of 90 years were positive for the disease. In summary, the prevalence of gallstone disease in our very old nursing home population was found to be unexpectedly high.

Measurability of non-small-cell lung cancer on chest radiographs

Response rates to various drug regimens are determined in multi-center trials by radiographic measurement of tumor dimensions before and after treatment. The way in which lesions are measured may affect the reported results. Lesions due to primary lung cancer may be more difficult to assess than rounded peripheral metastases. No previous study has assessed the variability of tumor measurements in patients with primary lung cancer. Nineteen radiographs from 12 patients with non-small-cell lung cancer (NSCLC) were shown to 25 experienced readers on two separate occasions. Pre- and post-treatment (combined chemotherapy and radiotherapy) radiographs were first shown separately, unidentified and in random order. Three months later, they were shown side by side with the facility for comparison. A decrease in tumor size of greater than or equal to 50% was considered as a "response." Viewing paired films together increased the viewers ability to measure tumors compared with reading each film of the radiographic pair individually. Fifty-one percent of unmeasurable pairs became measurable when read together, whereas 13% of previously measurable pairs now became unmeasurable. The interobserver variation in measurements was 10% to 265%, while the intraobserver variation was 4% to 10%. The correlation between responses calculated on the first and second readings often was no better than chance alone. Subjective impressions of degree of improvement showed no good correlation with response rates measured objectively. Because of the large variation in measurements and consequently in response rate, we recommend that all radiographs be reviewed by a single observer for any particular study, and pre- and post-treatment radiographs be evaluated together.

Lung scanning with 67gallium citrate for detection of acute radiation changes

Radiogallium imaging plays a growing role in the investigation of acute and chronic inflammatory diseases of the lung. We studied a series of patients undergoing radiation treatment for carcinoma of the breast to evaluate the usefulness of imaging with 67gallium citrate in the detection of early radiation changes in the pulmonary parenchyma. In a series of 12 patients there was no correlation between the clinical and radiographic manifestations of radiation pneumonitis and the gallium scan.