The labs say that getting high 3 times over 90 days will cause a positive hair test result. You haven't smoked in 4 months and like I said they can only go back 3 months because it becomes inaccurate after 3 months because the chemicals in the hair begin to degrade. About the test being least sensitive for THC, I don't think that is right. This is from Quest and it is the levels they use for positive confirmation. If you notice, THC has the lowest threshold by far.

http://questdiagnostics.com/employer...esting_es.html