ARCHIVED - Special Report of the Canadian Tuberculosis Committee

 

Tuberculosis and HIV co-infection in Canada

Canada Communicable Disease Report

15 April 2007

Volume 33
Number 08

M Phypers, BSC PT, MSC, MPA (1)

  1. Tuberculosis Prevention and Control, Public Health Agency of Canada, Ottawa, Ontario.

Introduction

The HIV epidemic has had a dramatic impact on tuberculosis (TB) rates and TB control in both industrialized and low-income countries. The virulence of TB and HIV increases synergistically. TB causes more rapid deterioration of the immune system of people with HIV or AIDS. In the absence of antiretroviral therapy, individuals with TB and HIV infection are as much as 100 times more likely to have active TB during their lifetime as people who are HIV negative, making HIV the most potent predictor of progression to active TB disease(1-4). Globally, TB is the most common cause of death in HIV-infected individuals (5). Of all adult TB cases aged 15 to 49 reported globally, 9% are attributable to HIV/AIDS(6).

TB-HIV co-infection in Canada

Despite close links between these two pathogens and increasing efforts to address both concurrently, uptake of screening policies linking HIV and TB has been slow(7). Universal HIV testing for newly diagnosed TB cases and TB assessment for all newly diagnosed HIV cases has been recommended in Canada for over a decade(8,9). Despite this, evidence suggests that universal testing for HIV of new TB cases is not occurring(10). A review of TB cases from 1997 and 1998 reported to the Canadian Tuberculosis Reporting System (CTBRS) found that the percentage of TB cases with a record of an HIV test was only 21.1%(11).

Several published Canadian studies have been conducted to determine the overlap that exists between TB and HIV. However, methodologies vary widely. Estimates of individuals with HIV or AIDS and active TB range from 1.6% to 5.8%(12-16). Studies conducted in Montreal and British Columbia estimated HIV infection among TB disease cases at 3.8% and 13.8% respectively(17,18). The CTBRS study referred to above found that among those whose test results were known the prevalence of HIV infection was 15.0% (3% coinfection for the entire cohort)(11).

Corbett et al. have estimated that 10% to 19% of adult TB cases in Canada are attributable to HIV(6). The World Health Organization (WHO) has estimated HIV prevalence among adult incident TB cases in Canada in 2004 to be 8.7%(5).

The CTBRS captures information on HIV coinfection for all TB cases reported in Canada. Between 1997 and 2004, the proportion of TB cases for which HIV status was known increased from 5.7% to 23.2%(11) (Figure 1). Reporting by province/territory for 2004 is shown in Table 1. Determining the Canadian incidence of TB-HIV coinfection from this surveillance system is not yet possible. In 2004, HIV status was reported for only 23% of cases, of which 10% were HIV seropositive. In the unlikely event that these were the only coinfected cases, the overall coinfection rate would have been 2%. Additional epidemiologic information (i.e. age, sex and ethnicity) for coinfected TB cases cannot be determined from this system because of the paucity of the data. Information from other sources have identified two important subpopulations at greater risk of TB-HIV coinfection: Aboriginal peoples and new immigrants to Canada.

Aboriginal

First Nations populations are at considerable risk of both TB and HIV and, as a consequence, at very high risk of TB-HIV co-infection(8,19). Although the rate of TB-HIV coinfection appears low in First Nations communities, limited data make it impossible to make an accurate determination(20). A 1999 report of the First Nations and Inuit Health Branch, Health Canada, reported only isolated cases of coinfection in the First Nations on-reserve population.

Immigrants

In 2002, Citizenship and Immigration Canada began mandatory HIV testing as part of the immigration medical examination (IME)*. From January 2002 to September 2006, approximately 2,400 individuals were identified as HIV positive during the IME process. The majority of these individuals are admissible on health grounds to Canada and come from TB-endemic countries. Therefore, the potential for TB-HIV coinfection in this population is likely significant.

Discussion and conclusions

The level of TB-HIV coinfection in Canada is uncertain. Estimates range from 1.6% to 19%. Data such as those reported to the CTBRS are inadequate to measure the HIV positivity among TB cases or to further define subgroups of TB patients at higher risk of HIV infection. In Canada, coinfection is likely to become more important, particularly in immigrants and refugees from countries with a high incidence of TB and HIV, and in Aboriginal peoples.

*An immigration medical examination is required for all applicants for permanent residency (i.e. immigration) and certain temporary residents (depending on such factors as anticipated length of stay in Canada, originating country and intended occupation in Canada).

An HIV test is required as part of the immigration medical examination for

- all individuals aged ≥ 15; - those < 15 years of age if there are known risk factors.

What the CTBRS data do demonstrate, however, is that universal testing and reporting is not occurring, despite the fact that TB patients constitute a high-priority group for epidemiologic surveillance for HIV and despite the long-standing existence of recommendations for universal testing and reporting(9).

In order to accurately assess the extent of TB-HIV coinfection in Canada and to ensure that effective treatment and appropriate care and prevention programs are provided, a further increase in testing and reporting is essential.

Figure 1. Proportion of TB cases reported in Canada for which HIV status was known: 1997-2004

Figure 1. Proportion of TB cases reported in Canada for which HIV status was known: 1997-2004

Acknowledgement

The author acknowledges the members of the Canadian Tuberculosis
Committee and the provincial and territorial tuberculosis programs for their contribution and participation in the Canadian Tuberculosis Reporting System:

Alberta Health and Wellness
Disease Control and Prevention Branch

Division of Tuberculosis Control
British Columbia Centre for Disease Control

Manitoba Tuberculosis Control Program

Department of Health and Wellness
New Brunswick

Department of Health and Community Services
Newfoundland and Labrador

Department of Health and Social Service
Government of Northwest Territories

Office of the Chief Medical Officer of Health
Nova Scotia Department of Health

Department of Health & Social Services
Government of Nunavut

Vaccine Preventable Diseases and TB Control Unit
Ontario Ministry of Health and Long-Term Care

Department of Health and Social Services
Prince Edward Island

Direction de la protection de la santé publique
Ministère de la Santé et des Services sociaux, Quebec

Tuberculosis Control Program
Saskatchewan Health

Department of Health and Social Services
Yukon

Association of Medical Microbiology and Infectious Disease
Canada

Canadian Lung Association

Canadian Public Health Laboratory Network

Citizenship and Immigration Canada

Correctional Service of Canada

First Nations and Inuit Health Branch,
Health Canada

National Microbiology Laboratory,
Public Health Agency of Canada

Tuberculosis Prevention and Control,
Public Health Agency of Canada

Table 1. HIV status among TB cases in Canada by province, 2004 (percentage of cases with known HIV status)

HIV status Canada Alta. B.C. Man. N.B. Nfld. N.W.T. N.S. Nun Ont.* Que. P.E.I. Sask. Y.T.

Negative

336

89

128

42

5

 

10

2

16

2

40

 

 

2

Positive

38

2

15

9

 

 

 

 

 

7

5

 

 

2

Test not offered

1

 

1

   

3

               

Test refused

2

 

2

                     

Unknown

1236

18

153

93

5

7

 

6

16

691

174

1

70

2

TOTAL 1,613
(23.2)
109
(83.5)
299
(47.8)
144
35.4)
10
(50)
7
(0)
10
(100)
8
(25)
32
(50)
700
(1.3)
219
(20.5)
1
(0)
70
(0)
4
(50)


References

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  17. Geduld J, Brassard P, Culman K, et al. Testing for HIV among patients with tuberculosis in Montreal. Clin Invest Med 1999 Jun;22(3):111-8.

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  19. Global tuberculosis control - surveillance, planning, financing. WHO Report 2006. WHO/HTM/TB/2006.362

  20. Public Health Agency of Canada. Tuberculosis in Canada, 2004. Minister of Public Works and Government Services Canada; 2007.

* An immigration medical examination is required for all applicants for permanent residency (i.e. immigration) and certain temporary residents (depending on such factors as anticipated length of stay in Canada, originating country and intended occupation in Canada).

An HIV test is required as part of the immigration medical examination for - all individuals aged ≥ 15; - those < 15 years of age if there are known risk factors.


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