Up until the birth of the EtG, tests used for forensic drug and alcohol monitoring had to go through the arduous, expensive and necessary FDA approval process. The LDT pathway was designed to develop simple tests with little risk that have low market potential (i;e. the cost of the normal FDA approval process would prohibit them from coming to market). The LDT pathway was designed to improve patient care in the diagnosis and treatment of patients. It was not designed for forensic tests. LDT approval does not require in vivo testing. It is essentially an honor system and to develop an LDT it is not even necessary to prove that the test is actually testing what it is purportedly testing for (validity).
So with little to no evidence base an ASAM/FSPHP physician introduced the EtG, had it developed and marketed as a LDT in collusion with unscrupulous labs, and then began using it on physicians being monitored by State PHPs. This then spread to other monitoring organizations in which there was a large power-differential between those ordering the tests and those being tested (criminal-justice, other professional monitoring programs). These biomarkers have never been used in Federal Drug Testing, SAMHSA approved, DOT, and other organizations where unions or other organizations are present and looking out for the best interests of those being tested.