What is a false negative drug test? - City of drug testing (2023)

Most people are familiar withfalse positives on drug tests, but are unaware of false negatives. What is a false negative on a drug test, what can you do to avoid it, and what should you do if you spot one?

What is a false negative drug test?

A false negative is any time when, under normal circumstances, a drug test would be positive for an individual, but for some reason the results are negative. An example would be an oxycodone prescription patient who consistently takes the prescribed medication but has a negative drug test during the doctor's visit.

In most cases, this is because the patient alters his urine sample on purpose or accidentally. The most common false negative drug test is due to water loading.

False negatives of water charging and adulteration

Water charging is the process in which a person drinks an excessive amount of water before giving a sample. Clear urine without yellow coloring is usually indicative of water load. You will need to run separate tamper tests for creatinine, pH, and protein levels to demonstrate that a test has been diluted by an individual who has ingested excessive amounts of water.

Without adulteration tests, pure water will show a negative result on a drug test test because the tests are only intended to detect the presence of a particular drug or metabolite in a substance, not to detect whether the substance is a valid sample. . Subjects can simply add water to their urine, but to deceive a witness, they drink an excessive amount of water to dilute the urine that comes out of their own body.

There are several products available that claim to help users pass urine drug tests. These products range from nothing more than fortified tea that dilutes the urine to products that claim to seal in fat cells for several hours. Many of these products speed up the amount of time a person can pass a urine test, even if it's no more than diluting the urine.

Incorrect selection of drug tests

One mistake that drug testing organizations make is incorrect test selection. Each organization will have its own considerations when choosing a testing device, but some drug tests will not detect all illicit substances that people assume.

semi-synthetic opiates

Often, a physician prescribes their patient oxycodone or another semi-synthetic opioid, but uses a 5-panel drug test that only has one test for opioids. The doctor saw his patients who were prescribed oxycodone test positive for opioids, but his new patient tested negative.One study found that oxycodone was detected in 12% of opioid immunoassay tests, and many other synthetic or semi-synthetic opioids also require a special test for accurate results.

Benzodiazepines

Most benzodiazepine assays detect their presence in urine by testing nordiazepam and oxazepam, the major metabolites of most benzodiazepines. Agents that follow a different metabolic pathway, such as triazolam, alprazolam, clonazepam, and lorazepam, show little cross-reactivity with the assay due to the absence of these metabolites and therefore often produce false-negative results. Some physicians prescribe diazepam, oxazepam, and temazepam to reduce laboratory confirmations.

False negatives from cut-off levels that are too high

If your drug tests have high cutoffs, a user who has recently used drugs is more likely to produce a negative result.

HeNational Institute on Drug Abuseit's himSubstance Abuse and Mental Health Services Administrationpublish the recommended cut-off levels for drug testing that most companies follow. Dozens of other federal agencies publish their own default limits (everyone from the Department of Transportation to the Nuclear Regulatory Commission) that are often based on federal recommendations.

Although the federal government publishes its own guidelines, labs and manufacturers can create products that use any cutoff level they deem appropriate, and federal guidelines change from time to time.

For example, opiates and morphine have two cut-off levels that have been widely used since the early 2000s because many people were failing job tests due to the popularity of poppy seed muffins. The recommendation skyrocketed from 300 ng/ml to 2,000 ng/ml. Most tests will use this recommendation to meet as many federal regulations as possible, but highly sensitive tests are still available.

In practice, there is no correct answer. Some regions may have popular restaurants that sell poppy seed muffins, and some industries may have a high percentage of customers who anticipate testing and use gray hat tampering methods to keep their levels below the threshold.

human error

We advertise our drug tests as 99% accurate, but in any situation involving a human being there is the possibility of introducing human error. A technician can mislabel labels, forget to confirm the temperature on a sample, or give the patient the opportunity to completely change a sample.

Human error is even more likely in a lab where a technician needs to set up a test, control variables, process and record information, and interpret results. Never completely rule out human error and implement procedures that can help reduce the likelihood of human error.

faulty device

Since the consequences of a failed drug test can be so severe, a lot of work and investment goes into quality control of drug testing devices. Still, there are always some faulty tests or test batches that slip through the cracks.

If you have multiple tests in a row that give unexpected results, consider that the tests might be faulty. It is very cheap and easy to use a second drug test if a subject says his results are not accurate.

Our drug test cups are designed to alert the user when there is a problem with the device itself. The control line can alert you to tampering, faulty testing, and some forms of incorrect collection.

Note that a12 panel drug testthere are actually 12 individual tests; most of the time a bad device means only one of the strips is bad. A certain percentage of faulty tests is expected in this industry, so we offer a 100% satisfaction guarantee that covers any faulty device and any additional tests you use to fix a potential faulty test.

Other anomalies

There are times when all the devices are working properly, everyone has done everything they are supposed to do, and a sample is valid in every way, and there is still a false negative result on the drug test.

the hook effect

A rare cause that has been addressed by manufacturers in recent years is the "hook effect," in which so much drug is present in the urine that there are no more binding sites on the antibody. This can cause a lower apparent level which could lead to a negative result if below the cut-off level.

drug degradation

One of the benefits of using a drug test cup is that the receptacle is also the test. There is no time gap between collection and testing. In a busy doctor's office, technicians can be distracted or intentionally multitask when working on test results.

When sent to a lab, it can take even longer between collection and testing. Time in transit and whenever the shipment sits in the lab without adequate refrigeration gives the sample more time to naturally degrade.

Most metabolites are stable for the brief periods usual in drug testing, but others are not stable, especially when subjected to temperature changes or extremely high temperatures.

An example is 6-monoacetylmorphine (6-MAM), a metabolite of heroin. On bodyheroin is metabolized to 6-MAM, which is then metabolized to morphine.6-MAM lacks stability, is subject to in vitro hydrolysis, and also continues to be metabolized to morphine even after urine leaves the body. One study showed that within 7 days at room temperature, a urine sample that tested positive for 6-MAM was completely hydrolyzed to morphine.

Limiting false negatives in drug tests

Understanding that a false negative is a possibility and the possible causes is the first step in stopping them. Collecting and storing data can be an important part of investigating unexpected or suspicious results.

With sufficient knowledge and proper analysis, many drug test results inconsistent with expectations can be reconciled and explained. Here are some other tactics you can use to limit the chance of false negatives in your drug testing program.

• Institute procedures and policies to combat the charging and adulteration of water.
• Use a 12-panel drug test to cover many of the synthetic and semi-synthetic opioids
• Understand cutoff levels and detection times for the tests you use
• Institute policies and procedures that reduce the likelihood of human error
• Report faulty tests to the manufacturer or reseller