I quit smoking pot after smoking everyday for a while. It's now been 45 days and I have passed at home tests. Can I pass a lab test?

Depends on the test. There are many different types of tests- even if it is a urine test different labs use different specific tests. It is likely you will pass a lab test but i can't guarantee it. See http://www.Canorml.Org/healthfacts/drugtestguide/drugtestdetection.Html for more information.