I have not heard of this happening if someone was to get HCV and HIV at the same time. If someone immune system was working well and they had HCV and HIV passed to them at the same time we would expect the window period would be the same for both infections as their immune system is in good health and would mount a response. Our immune systems are used to multitasking.
If someone already had HCV and you are wondering if the HIV window period would be affected. I have not heard of this happening. We do not have any special guidelines saying that people with HCV need to consider a different window period when testing for HIV.
Things can get a bit tricky if someone already has HIV and they were wondering if HCV had passed to them. Immunosuppressed people can show delays in antibody response. This is why I always suggest that anyone with HIV should have regular visits with their HIV specialist as that would be the person that would know what condition the immune system is in and if any special consideration needs to be taken into account when doing screening test or managing preventable infections with vaccines.
Currently with the 4th gen HIV test we use in BC we would find it unusual for someone not to show a positive result at 50 days if HIV had been passed to them, but our lab recommends a follow up test at 90 days just to make sure. The 4th gen HIV test is an antigen and HIV antibody test. The test looks for the P24 antigen. This test can detect the p24 protein on average 10 to 14 after HIV was passed to you, the p24 level peak at about 3-4 weeks and are usually not detectable after 5-6 weeks. Have a look at our “Understanding the window period of HIV tests” for a visual diagram on this.
In answer to your question p24 would not be detected indefinitely we would expect that none would be detected by 6 weeks. A 4th gen test would provide a high degree of accuracy when testing at 10 weeks you would be looking at 99% accuracy. The only thing that would change this accuracy would be if you had a medical condition that made you immunosuppressed or had taken something Like PEP for a HIV exposure.
If you have some additional information from what you have read on the internet like research studies, case reports, feel free to send us links to these. I know it can be difficult when doing research on the internet as information about medical conditions and testing technologies seem to be advancing at a fast pace.
Let us know if this does not answer your question or if you have any additional questions or concerns.