Amidst all the posts on which Anti-virus product is the best, I found this article interesting.

How to rate a comparative anti-virus test a six-step guide | Naked Security

Today I'll focus on comparatives and group tests.

This is a much murkier area of the testing world, with certifications tending to be limited to well-known, usually well-respected expert testers.

On the other hand, it sometimes seems like anyone with a computer and more than one brain cell feels qualified to do comparative testing.

There are a lot of pitfalls to look out for, which often trip up unwary would-be testers, and regularly lead to wonky data and biased, inaccurate and occasionally completely off-the-wall conclusions.
At the end of the article there's a useful link to some AV-testing labs.

There are several highly professional expert labs (the people at AV-Comparatives recently pointed me at a useful list of some of them), whose output should be reasonably reliable.
Although it's on the Sophos website, I'm not sure that the author works for Sophos; it says he is:
Technical Consultant and Test Team Director at Virus Bulletin, running independent anti-malware testing there since 2006.
But don't take my word for it - find out for yourself.