For Monkeypox Testing, Use Lesion Swab Samples to Avoid False Results: FDA Safety Communication
Date Issued: July 15, 2022
The U.S. Food and Drug Administration (FDA) is advising people to use swab samples taken directly from a lesion (rash or growth) when testing for the monkeypox virus. The FDA is not aware of clinical data supporting the use of other sample types, such as blood or saliva, for monkeypox virus testing. Testing samples not taken from a lesion may lead to false test results.
Use lesion swab samples when testing for the monkeypox virus.
- Test users and caregivers:
- Be familiar with the Centers for Disease Control and Prevention’s (CDC’s) information on monkeypox, including the current outbreak.
- Talk with your health care provider if you have symptoms of monkeypox or if you think you had contact with someone who has monkeypox.
- Talk with your health care provider if you were tested for the monkeypox virus using a sample type other than a lesion swab sample.
- Health care personnel:
- Be aware of the CDC’s Information for Health Care Professionals, including clinician FAQs and preparing and collecting specimens for monkeypox virus testing.
- If your patient was tested for the monkeypox virus using an alternate sample type and you suspect an inaccurate result, consider retesting your patient using a lesion swab sample.
- Test developers and laboratory personnel:
- Be aware of the CDC’s Information for Laboratory Personnel that includes information about procedures, testing, preparing and collecting specimens, and recommendations for clinicians.
- Contact the FDA at MPXDx@fda.hhs.gov to discuss new test development and alternate testing approaches, and to share validation data from saliva, blood, or any other sample types.
- Report any problems you experience with monkeypox virus tests to the FDA, including suspected false results. See Reporting Problems to the FDA.
Monkeypox Test Description and Background
Monkeypox virus tests are used to determine if a person is infected with the virus that causes monkeypox, which is a type of orthopoxvirus. The CDC’s FDA-cleared non-variola orthopoxvirus test can detect monkeypox from a lesion sample. This test is performed in many laboratories included in the CDC’s public health Laboratory Response Network (LRN) as well as additional large reference laboratories to facilitate monkeypox testing capacity and access.
There may be laboratory developed tests (LDTs) available for orthopoxvirus, or specifically for the monkeypox virus, which have not been reviewed by the FDA. LDTs are tests that are designed, manufactured, and used within a single CLIA-certified laboratory that meets the requirements to perform tests of high complexity. The FDA has generally exercised enforcement discretion for LDTs, meaning that, except in certain circumstances, the FDA generally does not exercise its authority to enforce the regulatory requirements for these devices, although it maintains that authority.
The FDA continues to monitor the situation with respect to appropriate policies for monkeypox tests.
Potential Risk of False Monkeypox Test Results
- False-negative monkeypox test results mean the test says the person does not have monkeypox, but they do have monkeypox. A false-negative result may lead to delayed diagnosis or inappropriate treatment. False-negative results can also lead to the infected person not taking action to limit their exposure to others, and further spread of the monkeypox virus.
- False-positive monkeypox test results mean the test says the person has monkeypox, but they do not have monkeypox. A false-positive result may lead to a delay in a correct diagnosis or the right treatment for the actual cause of the person’s illness, which could be a disease other than monkeypox.
Since the United States detected its first case of the 2022 monkeypox outbreak, the FDA has worked with the CDC, commercial laboratories, and manufacturers to make monkeypox tests more readily available to patients and providers who need them.
The FDA is working closely with the CDC to increase production and distribution of the FDA-cleared CDC non-variola orthopoxvirus test. The FDA also cleared the use of additional reagents and automation to increase the testing capacity of laboratories using the CDC test.
For monkeypox LDTs, the FDA has been following its usual approach with respect to enforcement discretion. The FDA is also working with the CDC concerning the non-variola orthopoxvirus test to speed distribution and increase testing capacity.
The FDA is providing this information to help educate test users, caregivers, health care personnel, test developers, laboratory personnel, and the public and to reduce the risk of false test results that could lead to increasing spread of the monkeypox virus.
The FDA will keep the public informed if significant new information becomes available.
Reporting Problems to the FDA
If you think you had a problem with a monkeypox test, the FDA encourages you to report the problem through the MedWatch Voluntary Reporting Form.
Health care personnel employed by facilities that are subject to the FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.
If you have questions about this Safety Communication, email the Division of Industry and Consumer Education (DICE) at DICE@FDA.HHS.GOV or call 800-638-2041 or 301-796-7100.