I don't understand why this test is necessary if a patient first responds positively to reflux medication. Then after a few months, it should be followed with an endoscopy to make sure the erosions have healed.
I think you need to use common sense about what tests you will undergo. What will the test really tell your doctor? That you do, indeed, have reflux? Doctors also consider a positive response to PPIs a diagnosis of reflux, however indirect. Doctors make money by performing these tests, or else they CYA by sending you to a specialist. You can get the PPIs from your PCP and simply schedule a follow-up endoscopy with a gastro.
Are you on a PPI right now? Are you on 1 dose a day or 2 doses a day? I wouldn't test for anything without having first gone up to a 2 dose per day schedule (if the 1 dose per day didn't work).
If the 2 dose per day regimen doesn't work, then I'd consider further testing.