There anyway you can pass a home test but fail a lab test?
A more common reason is the person had taken a home test during the latter parts of the day (after consuming fluids) and then took the scheduled U/A the next morning. Thats why whenever a person uses a home test, s/he should always use the first urination of the day when THCA concentrations would be at their highest. If youre consistently testing negative with the first urination of the day, youre good to go.