You’re correct that HIV-1 represents the significant majority of HIV infections across the world. Group M is the biggest group, followed by O.
The p24 antigen / antibody HIV test (also known as the 4th generation HIV test) detects p24 antigens for HIV-1 (Groups M and O), and antibodies for HIV-2. The p24 test does not reflect Groups N and P as they are very rare and not been found outside of Africa.
If you are testing after a potential exposure that you had in Canada, you can feel confident in the p24 test will reflect any strains you could have been exposed to.
If you are testing after a potential exposure you had in Africa, then you may want to seek additional testing.
Please let us know if you have any other questions.