As far as AV labs tests go, they have to be scrutinized for discrepancies. For example, on the latest comparative from A-V Comparatives, Windows Defender had an unusually high false positive rate using a much smaller malware sample size. Whereas on the latest AV-Test business test, WD had a low FP rate for a much larger malware sample size.
Bottom line - take AV lab test results as a rough approximation in regards to a security solutions real world malware performance. Also always review as many test reports as you can from different AV labs and again, look for discrepancies.