From the Guidelines
Testing for measles should be done as soon as possible after the onset of symptoms, with the measles IgM antibody test being the most accurate method, especially when performed 3-4 days after rash onset 1. When a patient presents with suspected or probable measles, it is crucial to collect blood for serologic testing during the first clinical encounter. The serum should be tested for measles IgM antibody using an assay that is both sensitive and specific, such as the direct-capture IgM EIA method 1.
Key Considerations for Testing
- The timing of specimen collection in relation to rash onset is critical for correct interpretation of serologic data 1.
- Measles IgM may be detectable at the time of rash onset, peaks approximately 10 days after rash onset, and is usually undetectable 30-60 days after rash onset 1.
- If measles IgM is not detected in a serum specimen obtained in the first 72 hours after rash onset, another specimen should be obtained at least 72 hours after rash onset and tested for measles IgM antibody 1.
Additional Testing Methods
- PCR testing of throat swabs or urine samples can also identify the measles virus, especially early in the infection 1.
- Serologic diagnosis of measles can also be confirmed by a significant rise in antibody titer between acute- and convalescent-phase serum specimens 1.
Importance of Testing
- Testing is crucial for confirming measles because its symptoms can resemble other illnesses, and confirmation helps public health officials track outbreaks and implement control measures 1.
- Measles is preventable through vaccination, so ensuring immunization is up-to-date is the best protection against infection 1.
From the Research
Testing for Measles
- Measles is a highly contagious illness that can be confirmed with laboratory testing, which is most commonly a serum immunoglobulin M 2
- The development of a live attenuated vaccine has greatly reduced the severity of MeV infection, but poor access to health facilities and anti-vaccination movements have prevented sufficient vaccination coverage 3
- A new RT-qPCR-based MeV detection assay has been developed, which has a higher threshold of 1-1.2 10^3 copies/mL and a joint diagnostic sensitivity of 100% when used with ELISA 3
- The real-time RT-PCR approach is more sensitive and appears to be a more promising method for measles diagnosis during early stages of the disease 3
- ELISA formats vary, and the sensitivity and specificity of each assay can range from 50 to 83% and 86.9 to 98%, respectively 4
- Detection of measles-specific IgM in serum by enzyme-linked immunosorbent assay (ELISA) is the most common method used to confirm measles infection, but interfering substances can yield false-positive results 4
- RT-PCR can be used to detect viral RNA from serum for molecular diagnosis of measles, especially in the first 3 days after rash appearance 5
- The performance characteristics of a measles IgM assay should be carefully considered when selecting an assay to achieve high-quality measles surveillance 4
- Timely recognition and laboratory confirmation of infected individuals, as well as appropriate infection prevention measures, are crucial to avert further transmission of measles 6