For detecting measles, a throat (oropharyngeal) or nasopharyngeal (NP) swab is the preferred sample type. These swabs are used to collect respiratory specimens for polymerase chain reaction (PCR) testing, which detects the measles virus's RNA. While throat swabs are commonly used, nasopharyngeal swabs, or even nasopharyngeal aspirates (NPAs), can also be effective.
Types of Swabs and Collection Methods:
- Throat (Oropharyngeal) Swab: This swab is collected from the back of the throat.
- Nasopharyngeal (NP) Swab: This swab is inserted into the nasal passage and collected from the nasopharynx (the upper part of the throat behind the nose).
- Nasopharyngeal Aspirate (NPA): This involves suctioning fluid from the nasopharynx, providing a more concentrated sample.
Important Considerations:
- Swab Material: Use swabs with plastic shafts; avoid cotton swabs or wooden handles.
- Transport Medium: Collected samples should be placed in 3 ml of liquid viral transport medium to preserve the virus for testing.
- Timing: Samples should ideally be collected within 7 days of the onset of a rash (if present). For urine samples, collection within 14 days is acceptable.
These recommendations align with guidelines from various sources, including the Illinois Department of Public Health (https://dph.illinois.gov/topics-services/lab-testing-services/clinical-testing/measles-submission-instructions.html), and other public health agencies, which emphasize the importance of using throat or nasopharyngeal swabs for reliable measles detection. These agencies often specify that PCR testing is the preferred method for diagnosing measles in both hospitalized and non-hospitalized patients.
