49 CFR 40.177 - What does the second laboratory do with the split specimen when it is tested to reconfirm the presence of a drug or drug metabolite?
(b) You must conduct this test without regard to the cutoff concentrations of § 40.87.
(c) If the test fails to reconfirm the presence of the drug(s)/drug metabolite(s) that were reported positive in the primary specimen, you must conduct validity tests in an attempt to determine the reason for being unable to reconfirm the presence of the drug(s)/metabolite(s). You should conduct the same validity tests as you would conduct on a primary specimen set forth in § 40.91.
(d) In addition, if the test fails to reconfirm the presence of the drug(s)/ drug metabolite(s) reported in the primary specimen, you may send the specimen or an aliquot of it for testing at another HHS-certified laboratory that has the capability to conduct another reconfirmation test.