Hello from JustAnswer.
Yes, Labcorp uses a panel test for initial screening, in some ways similar to the over the counter test, but also in some ways different.
The usual process for Labcorp is to first perform a screening test and then only perform a confirmatory test if the screening test is positive. The screening test is an immunoassay type of test, so is similar in method of the over the counter test. All immunoassay tests have a certain amount of false positive results, which is why a confirmatory test, such as gas chromatography/mass spectrometry (or GC/MS), is done.
However, Labcorp offers many different panels of differing scope, such as a 5-drug
panel and a 10-drug panel. Labcorp is also willing to work with any company to develop a custom panel. It is impossible to know the scope of the test solely because it was done at Labcorp, it is possible that the scope of the test involved drugs that were not included in the over the counter test.
So, Labcorp does perform a panel screening test and will stop if it is negative and only perform further testing if the screening test is positive. However, Labcorp offers several different panels, so may perform testing for drugs that are not included in the over the counter test.
If I can provide any further information, please let me know.