From the Guidelines
Measles diagnosis should be primarily done through a combination of serological tests detecting measles-specific antibodies (IgM and IgG) and molecular tests such as PCR on respiratory specimens, throat swabs, or urine samples to identify viral RNA, as recommended by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM) 1. The diagnostic approach for measles involves several key steps and specimen types.
- Serological testing for IgM and IgG antibodies against measles virus can be performed on cerebrospinal fluid and/or serum, with the optimum transport time being within 2 hours at room temperature in a closed container or clot tube (blood) 1.
- Molecular testing, such as PCR, can be conducted on various specimens including throat swabs, which should be placed in a viral transport device and kept on ice immediately after collection 1.
- Urine samples can also be used for PCR testing, and while the specific transport conditions for urine are not detailed in the provided evidence, it is essential to follow standard protocols for handling and transporting infectious specimens.
- The timing of specimen collection is critical, with IgM antibodies becoming detectable 3-4 days after rash onset and remaining so for about 28 days, and PCR testing being most sensitive within the first 3-5 days of symptoms. Given the contagious nature of measles and its potential for outbreaks, early and accurate diagnosis through a combination of clinical assessment and laboratory testing is crucial. This approach not only confirms the diagnosis but also facilitates public health measures such as isolation and contact tracing.
From the Research
Diagnostic Tests for Measles (Rubeola)
The diagnostic tests for measles (rubeola) include:
- Laboratory confirmation of measles virus infection based on a positive serological test for measles-specific immunoglobulin M antibody 2
- A four-fold or greater increase in measles-specific immunoglobulin G between acute and convalescent sera 2
- Isolation of measles virus in culture 2, 3
- Detection of measles virus ribonucleic acid by reverse transcriptase-polymerase chain reaction (RT-PCR) 2, 3, 4
- Measurement of IgM antibodies 3, 5
- Virus isolation using throat swabs and peripheral blood mononuclear cell (PBMC) samples 3
- Detection of measles virus RNA in PBMC by RT-PCR, which is considered the most effective method for diagnosis of measles 3
Alternative Diagnostic Samples
Alternative diagnostic samples that can be used for measles diagnosis include:
- Dried blood spots (DBS) 6
- Oral fluid (OF) samples 6 These alternative sampling approaches have the potential to be useful tools for measles control programs, especially in areas where patients may resist venipuncture for blood collection or where there are challenges with transport or refrigeration of diagnostic samples 6
Laboratory Diagnostic Methods
Laboratory diagnostic methods for measles can include:
- Indirect detection via antibody (IgM and IgG) detection methods 4
- Direct detection by viral culture or viral genome detection 4
- Genotyping of the measles virus to differentiate vaccine from wild-type strains, link cases and outbreaks, and track geographic spread and elimination 4
- Capture enzyme immunoassays (EIAs) for the detection of specific antibodies to measles virus 5
- Indirect EIA, in which antigen is directly absorbed to the solid phase, which is more sensitive than the capture design 5