Nucleic Acid Amplification Tests, or NAATs, are a type of molecular test designed to find specific genetic material in a sample. This genetic material, either DNA or RNA, can belong to a virus, bacterium, or even abnormal cells. Unlike other tests that look for proteins or the body’s immune response, NAATs directly identify the unique genetic code of a pathogen. This capability allows them to detect infections at very early stages, and the test’s precision makes it a valuable tool in clinical diagnostics.
The Amplification Process Explained
At its core, a NAAT works like a highly specific genetic photocopier. The process begins with the extraction of all nucleic acids from a patient’s sample. From this mixture, the test is designed to find and isolate a “target sequence,” which is a small, unique segment of DNA or RNA specific to the pathogen or cell being investigated.
The “amplification” step is what gives the test its name and its power. It takes the isolated target sequence and makes millions or even billions of identical copies. This rapid replication ensures that there is enough genetic material to be easily detected. The most widely recognized method for this amplification is the Polymerase Chain Reaction (PCR), though other technologies also exist.
This process of massive replication accounts for the high sensitivity of NAATs. By amplifying a minuscule starting amount of genetic material, the test can confirm an infection even when the pathogen is present at very low levels. Fluorescent markers are often used during this copying process, which release a signal as more copies are made.
Conditions Detected by NAATs
Due to their high sensitivity, NAATs are employed to diagnose a variety of infectious diseases. They are frequently used for respiratory infections, identifying the genetic material of viruses like SARS-CoV-2 (the virus that causes COVID-19), influenza A and B, and respiratory syncytial virus (RSV).
These tests are also a standard for diagnosing sexually transmitted infections (STIs). NAATs can detect the DNA of Chlamydia trachomatis and Neisseria gonorrhoeae with high accuracy from urine samples or swabs. For Human Immunodeficiency Virus (HIV), NAATs are used not just for initial diagnosis but also to measure viral load, which is the amount of HIV RNA in the blood. This information helps doctors monitor the effectiveness of treatment.
Beyond these common uses, NAATs are instrumental in identifying other types of infections. For example, they can detect Mycobacterium tuberculosis, the bacterium that causes tuberculosis, often more quickly than traditional culture methods. They are also used to find toxigenic Clostridium difficile in stool samples and to detect low-density malaria infections that might be missed by other methods.
NAATs Versus Other Types of Tests
NAATs are distinct because they detect the specific genetic material—DNA or RNA—of a pathogen. This means a NAAT can identify an active infection in its earliest stages, sometimes before a person has developed symptoms. Their ability to amplify trace amounts of genetic code makes them highly sensitive and specific.
A different approach is taken by antigen tests, such as the rapid tests often used at home for COVID-19 or the flu. These tests do not look for genetic material but instead detect specific proteins, known as antigens, that are found on the surface of a virus. While much faster at providing results, antigen tests are less sensitive than NAATs and can lead to false negatives in early or low-level infections.
A third category is antibody tests, also called serology tests. These tests do not detect the pathogen at all. Instead, they look for antibodies, which are proteins produced by the body’s immune system in response to an infection. A positive antibody test indicates that a person was exposed to the pathogen in the past. It cannot, however, determine if a person has a current, active infection.
The Testing Procedure for Patients
For patients, the process of getting a NAAT begins with collecting a biological sample. The type of sample depends on the suspected condition. For respiratory infections, this is commonly a nasal swab that collects material from the front of the nostrils or the nasopharynx. Throat swabs are also used. For some STIs, a simple urine sample is sufficient, while other tests may require a blood draw.
Once collected, the sample is sent to a laboratory for analysis. Inside the lab, technicians perform the nucleic acid extraction and amplification steps using specialized equipment. Patients can typically expect to receive their results within one to three days after the sample arrives at the lab, though some rapid NAATs can provide results in under an hour.