The Cheek Swab vs. Blood Testing for DNA debate has been around for a while. Most of the conversation surrounds issues of quality, but there are a number of other important factors to consider as well. Deoxyribonucleic Acid (DNA) testing is a technology used to test for a variety of reasons including testing for medical history, verifications of identity (mother, father, sibling, etc.), and to study ancestry. No matter what your reasons are for obtaining a DNA test, you are going to be as interested in how the test is conducted and how accurate those results are going to be.

Not all swab tests are the same

There are a variety of different methods for collecting saliva for DNA samples. These methods include dry and wet sample procedures.

Dry procedures require the donor to insert a buccal swab or other collection devices into the mouth, where tissue is scraped from the gum and cheek surfaces.  One of the challenges with this method is that if not done correctly, the sample may become contaminated with bacteria from the patient’s teeth and other surfaces.

Wet procedures include swishing liquids in the mouth (before the swab) and spitting them into a collecting vessel. Mouthwash may be used with this procedure to remove bacteria from teeth and other mouth surfaces. Some procedures ask the donor to simply spit into a collection device.  After providing a sample and closing the device, a solution is released from the cap to mix with the saliva.  This solution stabilizes the DNA for long-term storage at room temperature and helps to prevent bacterial contamination of the sample.

The basis for the sampling debate

The basis for the debate about the mouth swab method for collecting samples for DNA testing is about sample integrity, and some have questioned whether blood samples would be more accurate than buccal (cheek) swabs.

Since DNA is a blueprint of each person’s identity, it is much like a fingerprint. The person being tested gives a sample of their cells, which are then analyzed in a laboratory. The results show the unique chemical and biological makeup of a person’s body, and the identity factors within that information are unique.

The current preferred swab specimen collection technique for DNA testing is inside the mouth with a swab. When these swabs are taken, the technician gently scrapes inside the cheek for cells. While there are different types of DNA test methods , the cheek swabs are easy to collect and the samples are very easy to ship to the testing site.

The actual swab test itself is very easy and only takes a few minutes. The debate isn’t really about the genome test (which is done in the laboratory), but about the sample itself – how it is taken and under what circumstances. That’s why some have questioned whether blood samples would be more accurate than buccal swabs for certain situations.

Factors that may change the sample

Since the mouth swab test is collecting cells lining the mouth, it makes sense that eating, drinking, and smoking could affect the sample. Again, this is not the accuracy of the DNA test, but the quality of the cells obtained before they are sent away to be tested.

Eating something very hot or spicy or drinking alcohol or strong coffee could change the number and quality of the cells that are obtained in the sample. Also, medications taken by mouth could change the sample, and the results as reported by the lab could be inconclusive. In these cases, the laboratory reports that the test was inconclusive and request a second sample from the donor.

Testing benefits often favor the swab

Most medical experts agree that when the test is done correctly, the use of buccal swabs are not only as accurate as a blood test, but also provide a much easier technique for collection of DNA samples. When tests become complicated, there is always an increase in the probability of mistakes being made along the way. Simple tests favor the results; a simple test just has fewer steps for the donor and for the medical professional who will process the test sample.

Another benefit that favors the cheek swab method is that it doesn’t require refrigeration like the blood sample test does, and the blood samples are good for up to six months after the collection has been taken.  This reduces problems with quality control and increases the likelihood of getting an accurate sample. The laboratory technician finds it easier to keep the sample intact and readable before the laboratory obtains the results.

From the lab’s point of view, extracting the DNA for testing is a much simpler process when using buccal swabs as opposed to blood samples. When analyzing DNA for relationship testing, the same test method is used for cheek swabs or blood samples.

The swab tests are accurate as well. DNA testing reliability has advanced to the industry-accepted standard of 99.5 percent. Most experts agree the accuracy of a DNA test conducted with a cheek swab is equivalent to a test conducted using a blood test.

Special considerations and emerging concepts

Emerging concepts in the medical field may still favor and utilize blood testing in certain types of tests and for certain types of screenings. These tests are not for DNA specifically, but may also include white blood cells, which contain DNA information. These new emerging concepts also provide some insight into efforts being made to control costs of healthcare.

Red blood cells do not have any DNA, as they lose their nuclei (the compartment in a cell that contains the DNA) as they mature. So the DNA in your blood is in your white blood cells. To get at it, scientists first spin a small sample of your blood at high speed, to separate the cells from the blood fluid.

For example, new technical information published by the College of American Pathologists describes the study of how tumors in the body “shed” certain DNA material into the bloodstream, making detection of the growth or reduction process observable and measurable through a blood test sample. This is considered less invasive than surgery, so the term “invasive” is relative.

Other screenings, such as those conducted for blood sugar, have always used a blood test. But recently, the FDA has approved a new monitor that does not require a finger prick test. The pain of finger sticks and the cost of testing supplies discourage many people from keeping close tabs on their blood sugar, which is needed to manage insulin use and adjust what they eat.

The new device on the market is a way to measure glucose levels in real-time throughout the day and night. A tiny electrode called a glucose sensor is inserted under the skin to measure glucose levels in tissue fluid. It is connected to a transmitter that sends the information via wireless radio frequency to a monitoring and display device.

Connections between the blood sugar monitoring device can also be made to a person’s smartphone, alerting them of blood sugar levels and encouraging them to change diet, exercise, and/or medication to meet the new level in the blood.