POCT vs. Lab Testing: What Is the Difference?
While they have a common goal, POCT and lab testing are different in many ways — these guidelines will help you decide which is the right method for your company.
Drug testing and alcohol testing are a critical part of the hiring process because of the severity of the negative consequences of workplace substance abuse. Most employers are also of the opinion that performing drug tests prior to a new worker’s first day is not sufficient in maintaining a drug-free work environment. Companies believe that conducting drug tests on a random basis, as well as upon reasonable suspicion will further enhance the safety of their organizations. The most common type of drug testing is urine analysis, due to its ease of administration and cost-effectiveness. However, there are drug tests available for other sample types. (Learn more in "Oral Fluid, Urine, and Hair Testing: What's the Difference?"). Point of Collection Testing (POCT) and Lab Testing are the two primary types of urine drug tests.
Why is Urine the Preferred Biological Specimen Over Hair or Blood for Drug Testing?
Urine is referred to as the gold standard of biological specimen for drug testing among the medical community. In addition, this type of specimen is required in DOT testing. (Learn more in "8 Things Employers Should Know About DOT Drug and Alcohol Testing".) According to Dr. Howard A. Heit, urine is the best biological specimen for determining the absence or presence of certain drug metabolites because:
- Urine offers a longer window of detection period — the length of time a substance is detectable in a specimen — when compared to blood
- Urine drug testing is less costly than hair or blood serum testing (Learn more in "Hair Follicle Drug Testing 101").
- Urine collection for urine drug testing is non-invasive, simple for the patient, and convenient for both patient and employer
|Free Download: What Your Company's Drug and Alcohol Policy May Be Missing (and How to Get It Right)|
What is Point of Collection Testing (POCT)?
Point of Collection Testing (POCT) is a portable test that is done on site (the workplace) or at a specified testing location rather than the sample being sent to a laboratory. POCT is conducted using a wide range of devices which are designed to be self-contained and simple to use. As such, they are generally less costly and produce quick results. Generally, in a workplace setting, a urine sample is taken from the employee and the test includes an immunoassay reagent. The reaction between this reagent and the sample will produce a visual indicator (generally a line on a dipstick) if the employee has been abusing drugs.
Types of POCT
Some POCT devices can test for the metabolites of a single drug, while others can be used to test for the metabolites of several drugs. These include: opiates/opioids, cannabinoids, benzodiazepines, cocaine, barbiturates, methadone, amphetamines/methamphetamines, phencyclidine, and oxycodone. POCT devices available for workplace drug testing include but are not limited to:
- 5 Panel Urine Drug Test: Tests for marijuana, cocaine, opiates, amphetamines, and methamphetamines
- 6 Panel Urine Drug Test: Tests for amphetamines, marijuana, cocaine, methamphetamines, opiates, and phencyclidine.
- 10 Panel Urine Drug Test: Tests for methamphetamines, cocaine, amphetamines, opiates, oxycodone, phencyclidine, benzodiazepines, barbiturates, and methadone.
- 12 Panel Urine Drug Test: Tests for cocaine, marijuana, opiates, amphetamines, methamphetamines, phencyclidine, benzodiazepines, barbiturates, methadone, oxycodone, ecstasy, and propoxyphene
Advantages and Disadvantages of POCT
Like all drug testing methods, POCT has both advantages and disadvantages.
Advantages of POCT testing include:
- It is less expensive than laboratory testing.
- It is relatively easy to administer.
- It requires little training to administer the test.
- The test results are often available within minutes.
Disadvantages of POCT testing include:
- POCT can be less accurate and reliable compared to laboratory analysis.
- POCT devices are unable to distinguish between individual compounds, and therefore only report the class of drug. In other words, a POCT can test for the metabolites of opiates but not tell if it is specifically heroin.
- POCT devices often report false positive, especially if the employee is taking legal medications that fall into the same class of substance as illegal drugs.
- The sensitivity of the POCT device varies based on manufacturer, target compound and the threshold set for detection.
- The physical condition of the employee can affect test sensitivity.
What is Lab Testing?
Lab testing of a urine sample to detect drug abuse involves a two-stage process. The first stage is an initial screening test completed at an accredited laboratory using immunoassay technology. In this case, immunoassay technology has an accuracy rate of over 99 percent.
Screening tests are used to identify negative results, as well as specimen validity (the latter is to determine if the urine sample has been tampered with). (Learn more in "How to Avoid Adulteration in Employee Drug Testing"). Additionally, immunoassay screening tests cannot distinguish between drugs of a certain class. Therefore, positive screening tests are then confirmed by either GC/MS (gas chromatography/mass spectrometry) or LC/MS (liquid chromatography/mass spectrometry).
These confirmation tests are able to distinguish between drugs of a certain class, even at lower levels, confirming the absence or presence of certain drugs. Levels of lab testing will vary depending on regulations and laws a company is subject to and the company's own drug policies. For example, employees falling under Department of Transportation (DOT) testing regulations must be drug tested using specific methods outlined in the organization's regulations.
Advantages and Disadvantages of Lab Testing
According to the Australia’s National Research Centre on AOD Workforce Development the advantages and disadvantages of lab testing for drug urine testing are as follows:
- It is more reliable and accurate compared to on-site POCT.
- Lab testing uses confirmatory analysis to distinguish between drugs of a certain class.
- A lab test can detect whether or not a urine specimen has been tampered with prior to testing.
- The results can be stored for future medical or legal access.
- Lab staff have higher levels of expertise/training in the conduction and interpretation of tests.
- Lab testing is far more expensive than POCT.
- There is a slower turnaround time for test results.
What is the Difference?
The differences in a POCT and a lab test for drug urine analysis lie in factors such as ease of use, functionality, and cost. POCT utilizes specific devices designed for drug urine testing in which the worker’s urine is collected. The specimen can be immediately analyzed using a color banded, or numbered, dipstick, producing timely results. On the other hand, for lab testing, the worker’s urine must be sent to a laboratory, where it is first screened and then analyzed using highly sensitive and costly techniques.
Which Method Should Companies Use?
Much of deciding which method to use is a matter of comparing test capabilities to company goals. However, in some cases, government regulations will determine which drug testing method companies use and when they use them. For example, DOT regulations are very specific on the type and timing of drug testing for employees who fall under their purview.
For companies not restricted by government mandates, there are several factors to consider. While POCT may be cost effective, they produce a higher rate of false positives and false negatives than laboratory analysis. However, the risk of false positives can be reduced by subsequent confirmatory laboratory analysis or similar gold standard techniques. Therefore, as a result of the limitations of POCT devices, workplace testing programs are limited to a screening role, and is always recommended that all positive tests be confirmed by laboratory confirmation testing
Lab testing, on the other hand, is more expensive and time consuming than POCT. However, lab testing is more likely to meet legal standards should court actions result from testing and can provide more legal shielding to a company. Regardless of method used, a company should always have a written drug and alcohol policy.