HIV/AIDS Epi Update - May 2004

Prevalent HIV Infections in Canada: 30% May Not Be Diagnosed

Introduction

At A Glance

There were an estimated 56,000 people living with HIV infection (including AIDS) in Canada at the end of 2002.

Of these, approximately 17,000 or 30% are not aware of their infection.

Given the new treatments for HIV, it is more important than ever that all Canadians are able to access HIV testing.

This Epi Update presents the estimated number of Canadians who were HIV-infected but unaware of their infection at the end of 2002. It also summarizes available data on the characteristics of persons tested for HIV in Canada.

HIV Testing in Canada

Knowledge of one's HIV status can be useful for several reasons. Counselling received at the time of HIV testing can provide critical information about how to reduce the risk of HIV infection. If an individual is found to be HIV-infected, consideration can be given to starting antiretroviral therapy. In the case of pregnant women, treatment can reduce the chances that the infant will be infected, from about 25% to 8% or less.¹

Canadians have had the opportunity to be tested for HIV infection in Canada since the test became available in 1985. Individuals have accessed HIV testing services through either coded or confidential testing at a doctor's office or clinic, or through anonymous testing sites.

Positive HIV test report data are provided by all provinces and territories in Canada to the Centre for Infectious Disease Prevention and Control (CIDPC) and are presented in the most recent semi-annual report: HIV and AIDS in Canada: surveillance report to June 30, 2003.² They are based on non-nominal, confidential HIV testing information with duplicate tests for the same individual removed to the extent possible. The removal of duplicates is necessary to accurately reflect the annual number of new HIV diagnoses. Duplicate removal rates vary by year, province and type of data (nominal, non-nominal or anonymous). It is important to note that in most provinces the ability to remove duplicates has improved significantly since 1995.

HIV-infected but Unaware

There have been 52,680 positive HIV tests reported to CIDPC up to December 31, 2002.² After adjustment for under and delayed reporting, it is estimated that approximately 57,000 Canadians have tested positive for HIV from 1985 (when testing became available) to the end of 2002. Of this total, an estimated 18,000 individuals had died by the end of 2002 (also adjusted for under and delayed reporting). Therefore, of this 57,000 approximately 39,000 individuals were aware of their HIV infection and were still alive at the end of 2002.

It is important to note that data on positive HIV tests represent only those who have tested positive for HIV infection and do not represent all persons who have been infected with HIV as some who have been infected have not yet come forward for testing.

In December 2003, CIDPC published estimates of HIV prevalence in Canada to the end of 2002.³ It was estimated that approximately 56,000 (46,000-66,000) Canadians were living with HIV infection (including those living with AIDS) at the end of 2002. This number includes those who are aware of their infection (had a positive HIV test) and those who are unaware of their infection.

The difference between the total number who were HIV-infected and alive at the end of 2002 (56,000) and the number who were aware of their HIV infection and alive at the end of 2002 (39,000) represents an estimate of the number of persons unaware of their infection (had not yet tested positive for HIV) and alive. This difference is approximately 17,000 (13,000-21,000) or about 30% of the estimated 56,000 Canadians living with HIV infection at the end of 2002.

Characteristics of Persons Tested for HIV

A Canada-wide survey conducted in March 2003 of randomly selected individuals above 15 years of age revealed that just over one-quarter (27%) reported ever having been tested for HIV, excluding testing for the purposes of insurance, blood donation, and participation in research.⁴ In this survey, women were more likely to have been tested than men (29% versus 24%), and among people who reported having been tested, 42% had not been tested in the previous two years, 38% had been tested once in the previous two years and 18% had been tested twice or more in the previous two years.

The figures from this 2003 survey show that a higher proportion of individuals reported having been tested as compared with the results of a Canada-wide survey conducted in January 1997, when it was found that 18.6% of men and 16.2% of women aged 15 years and older had been tested for HIV (excluding tests for blood donation and insurance purposes).^5,6 Of those tested, 39% had been tested in the year before the survey, 57% in the previous two years, and 43% had had their most recent test more than 2 years before the survey. A 1996 survey found that, taking into account ancillary testing such as donating blood or being tested for life-insurance purposes, 41% of men and 31% of women in Canada had ever been tested for HIV.⁷

National surveys of the general population suggest that those who report risk factors are more likely to be tested:

• Among heterosexuals, those with two or more partners in the previous year were more likely to be tested than those with one partner (50.5% versus 17.4%). Of those who reported having had a sexually transmitted infection (STI) in the previous five years, 58% had been tested compared with 17.4% of those who did not report an STI.^5,6 The percentage of Canadians being tested is higher among individuals who reported casual partners (45%); this percentage increases with the number of partners, from 30% among individuals reporting one partner to 41% among those reporting two partners and 51% among those reporting three partners.⁴
• For men, testing was higher among those who had had sexual intercourse with men (71%), used injecting drugs (62%), received blood or clotting factor between 1978 and 1985 (27%), or had had a partner with a risk factor (injecting drug user [IDU], received blood or clotting factor between 1978 and 1985, origin in country endemic for HIV) (30%).^5,6 For women, testing was higher among those who had received blood or clotting factor between 1978 and 1985 (32%), had had a high-risk partner (38%), or had had sexual intercourse with a man since 1978 (17%).⁷
• Testing was highest among individuals aged 25 to 34 years. Even after all other risk factors are taken into account, those aged 45 years and over were still less likely to be tested than those younger than 45 years.^5-7 In the survey conducted in March 2003, Canadians aged 25-34 years and 35-44 years were more likely to be tested (46% and 35% respectively).⁴
• Targeted studies have shown that a large proportion of individuals in high-risk populations have been tested for HIV, though it is possible that some were tested for the purpose of participation in research. Among men who have sex with men (MSM) surveyed in B.C. in 2002, the proportion who reported ever having been tested was 89%.⁸ In the I-TRACK survey of IDUs conducted at selected centres across Canada in 2002-03, 89.7% of IDU reported having been tested for HIV.⁹
• Although those reporting risk factors such as IDU, multiple partners, or MSM are more likely to be tested, a substantial proportion of those reporting risk factors have not been tested recently, or have not been tested at all. For example, in the 1997 survey, among those who reported more than one partner in the previous year and not using condoms consistently, 53% of men and 38% of women had never been tested.^5,6

Comment

Canadians with risk factors for HIV infection are more likely to have been tested for HIV than those without such risk factors. However, there is still a significant proportion of persons with risk factors who have never been tested for HIV. It has been estimated that there are approximately 17,000 people or 30% of the HIV-infected population who are unaware that they are infected. More information is needed about individuals who are at risk of HIV but have not been tested. Given these data and the fact that new treatments are available for HIV infection, it is more important than ever that all Canadians be able to access HIV testing, particularly those at highest risk of infection.

References

1. Mofenson LM, McIntyre JA.
   Advances and research directions in the prevention of mother-to-child HIV-1 transmission. Lancet 2000;355:2237-44.
2. Health Canada.
   HIV and AIDS in Canada: Surveillance Report to June 30, 2003. Division of HIV/AIDS Epidemiology and Surveillance, Centre for Infectious Disease Prevention and Control, Health Canada, November 2003.
3. Geduld J, Gatali M, Remis RS, Archibald CP.
   Estimates of HIV prevalence and incidence in Canada, 2002. CCDR 2003;29:197-206.
4. HIV/AIDS - an attitudinal survey
   Summary of the findings
5. Houston SM, Archibald CP, Sutherland D.
   Sexual risk behaviours are associated with HIV testing in the Canadian general population. Can J Infect Dis 1998; 9(Suppl A):39A, #239P.
6. Canada Health Monitor Survey. Division of HIV Epidemiology, Centre for Disease Prevention and Control, Health Canada, January 1997 (unpublished data).
7. Houston SM, Archibald CP, Strike C, Sutherland D.
   Factors associated with HIV testing among Canadians: results of a population-based survey. Int J STD AIDS 1998;9:341-46.
8. Trussler T, Marchand R, Barker A.
   Sex NOW by the numbers: a statistical guide to health planning for gay men. Vancouver, BC: Community-Based Research Centre, 2004: 44.
9. Health Canada.
   I-Track: Enhanced surveillance of risk behaviours among injecting drug users in Canada. Pilot survey report. February 2004. Surveillance and Risk Assessment Division, Centre for Infectious Disease Prevention and Control, Health Canada, 2004

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