According to a survey conducted by the National Institute on Alcohol Abuse and Alcoholism in 2014, more than 87.6 percent of American adults drink alcohol at some point during their lives. More alarmingly, more than 24.7 percent of those adults admit to binge drinking on occasion, and 6.7 percent say that they engage in regular heavy drinking. As a result, alcohol is the most common addictive substance in the US, with around one in twelve adults having some form of dependency.

Rehab centers exist to get people off their dependencies on drugs and alcohol. But when it comes to alcohol, ensuring that the addictive behaviors have actually stopped can be a challenge. The problem is that traditional detection methods, like breathalyzer tests, rely on the presence of ethanol in the blood. Breathalyzers are ideal for law enforcement officials and other professionals who care about whether alcohol is present in the blood at any given moment, but they’re not so useful for those who want to detect whether a person has stopped using alcohol entirely. Breathalyzers also fail on another important front: they run the risk of generating a false positive. The problem is that ethanol can be detected in the blood for reasons other than direct alcohol consumption. For instance, sugars in dietary fruit can ferment into alcohol which is then absorbed by the stomach into the bloodstream, leading to a positive breathalyzer result, even though the individual concerned did not drink any alcoholic beverage. Rehab centers, therefore, are likely to see far greater from EtG tests, a particular type of test for alcohol that doesn’t rely on blood ethanol. EtG stands for ethyl glucuronide, and it is a direct biomarker of alcohol use, meaning that the body only produces this metabolite if a person has consumed alcohol in some form.

The great thing about EtG tests from the point of view of rehab centers is that it is not a contemporaneous test of alcohol consumption. In fact, it can be used to detect whether alcohol has been consumed by a person in any of the preceding four days. The reason for this is that small levels of EtG remain in the urine long after consumption, meaning that the window in which rehab centers can detect whether a person has relapsed is much larger than it is with standard tests. The benefits for rehab centers, therefore, are obvious. Unlike breathalyzer testing, EtG tests allow support staff and medical experts to determine whether somebody has actually stopped drinking.

Some laboratories are taking their testing a step further even than this. Many are now employing so-called “hair EtG tests” because it is much harder to adulterate samples. Hair testing is widely considered to be the new gold standard among rehab clinics since hair samples can be used to detect alcohol misuse up to three months ago.

Rehab centers, therefore, prefer EtG tests because they offer a longer detection window than standard breathalyzer tests and because the probability of a false positive is lower.