HIV-1 Strain and Primary Drug Resistance in Canada

Surveillance Report to June 30, 2001

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Data Limitations

The data presented in this report must be interpreted with caution for the following reasons:

• The data represent cases of newly diagnosed individuals for whom serum specimen and corresponding epidemiologic information are provided to Health Canada from provincial partners participating in the CHSDRSP. The data are based on convenience sampling and therefore do not include all newly diagnosed cases in a given population for any given year. Although we do not anticipate any biases introduced as a result of the convenience sampling, we need to bear in mind that the data are not representative of all newly diagnosed cases in the population.

• The data presented are only from those individuals who are infected with HIV who then seek testing. They do not represent individuals who do not know their HIV status or choose not to seek testing. Furthermore, they do not represent individuals for whom insufficient sample is available for strain and drug resistance genotyping.

• The data do not represent information from the two provinces that bear the burden of HIV infections - Ontario and Quebec. Work is already under way on mechanisms to include data from these provinces, and it is anticipated that one or both of them will be included in the next report on strain and primary drug resistance surveillance in Canada.

• Since this report is dealing solely with primary drug resistance (i.e. resistance seen among individuals who have never before received treatment), analysis was conducted on the laboratory specimens collected from treatment naïve individuals at the time of initial testing for HIV. However, treatment history cannot always be verified. At least 5% of laboratory specimens from B.C., for example, are likely to have been collected from individuals who have received treatment.

• At the time of writing this report, all data had been received retrospectively, so that the report actually describes what has happened historically. Although these data are still useful in informing program planning and policy formulation, their utility could be enhanced with "real-time" data. We anticipate that as the CHSDRSP moves towards the collection of prospective data, real time information will be presented in the report.

• Missing or unknown epidemiologic data remain problematic, particularly with respect to information on previous HIV testing, date of first positive HIV test, ethnicity, risk behaviour, CD4 and viral load at diagnosis, and previous anti-retroviral treatment.

• Subtype analyses are conducted on 1,053 base-pairs in the pol gene and reflect what is observed within this small region of the viral genome.

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