Measles Serologic Techniques
In areas with a low incidence of measles, the diagnosis of measles by clinical presentation is often complicated because of the sporadic nature of the disease and the widespread occurrence of other rash-causing illnesses. In addition, many measles cases in previously vaccinated or immunosuppressed individuals do not meet the clinical case definition. Therefore, confirmation of measles virus infection must be made using laboratory-based methods.
Antibody detection is the most versatile and commonly used method for measles diagnosis. In acute, uncomplicated measles, a significant rise in measles-specific IgG antibodies between acute- and convalescent-phase serum specimens is generally considered diagnostic. A positive test result for specific IgG antibodies in a single serum specimen indicates past infection with measles virus or measles vaccination, but does not ensure protection from infection or re-infection. Detection of specific IgM antibodies in a single serum specimen collected within the first few days of rash onset can provide a good presumptive diagnosis of current or recent measles virus infection. Therefore, the IgM assay is the test of choice for rapid diagnosis of measles cases.
The enzyme immunoassay (EIA) is the most commonly used method for detecting measles-specific IgM and IgG antibodies. Both capture and indirect formats for IgM detection are available commercially and most perform well. However, in countries where disease prevalence is low, intensified surveillance typically implemented during and after an importation will result in some false positive IgM results since no assay is 100% specific.
Serologic Specimen Handling
Blood for serologic testing is collected by venipuncture or by finger/heel stick into a serum-gel separator tube. Do not freeze the tube before serum has been removed. Centrifuge the tube to separate serum from clot. Aseptically transfer serum to a sterile tube that has an externally threaded cap with an o-ring seal. Fresh, sterile serum can be shipped overnight on wet ice pack. Hemolyzed and lipemic serum and plasma are noted and tested; usually without apparent interferences.
Arrival, Tracking, Reporting
Serum specimens for measles serologic testing (IgG, IgM) arrive at CDC through the Data and Specimen Handling Section (DASH) from international, state, and local health departments, and from PAHO and WHO reference laboratories. A completed DASH form (appendix: CDC 50.34 rev 11/92 ) must be submitted with the specimens. It is important to include the date of last measles vaccination if applicable, and the dates of rash onset and blood collection.
All specimens accepted are by prior approval of Dr. William J. Bellini, Chief of the MMR and Herpesviruses Laboratory Branch. Specimens are tracked by DASH and results are reported back through DASH to state health departments or WHO network laboratories. Raw data of all test results are kept on file. All results are reviewed by the laboratory supervisor.
Frozen serum is thawed at room temperature 1-2 hours or in the refrigerator overnight just prior to testing. Serum may be kept at 4˚C for several days to complete retesting before returning to -20˚C for long-term storage. As quantities permit, all serum samples tested are kept in long-term storage within the measles laboratory.
To ensure optimal test performance, it is essential that all test procedures be followed exactly as described in the package inserts:
- Working dilutions of the assay reagents must be prepared identically each time.
- Incubation times and temperatures must be strictly observed.
- Test reagents must be handled in the prescribed manner. To minimize freeze-thaws and to avoid contamination, use sterile technique to dispense reagents in small volumes but not volumes less than 50 ul.
- Lyophilized reagents, especially diluents, should be reconstituted to volume described and mixed vigorously on a mechanical mixer.
- High background signal.
- High background signal in scattered plate wells indicates poor washing technique or reagent cross-contamination. Clean washer and repeat test.
- High background in all plate wells may indicate improper reagent dilution or contamination of test reagents or diluents. Repeat test with new products.
- High background signal in uninfected cell control wells of a particular test specimen suggests unidentified serum antibody reactions with test reagents. The specimen may be retested in serial dilution.
- Special care should be taken to match patient identifiers with serum dilution tubes, with location of sera on test plates and with calculated O.D. values.
- A record should be kept of each assay as the test is performed. Note the reagents, lot numbers, and expiration dates. Record how dilutions are made and the timing of each step.
- A continuous record of all control values should be kept to monitor changes in assay performance over time.
|+||+ or -||not vaccinated, no
history of measles
|+||+ or -||not vaccinated, no
history of measles
|wild-type measles||seroconvert*, classic measles|
|+||+ or -||Previously vaccinated, primary vaccine failure||recent
|IgG level may stay same or boost|
|wild-type measles||may have few or no symptoms**|
|+||+||recently vaccinated||exposed to
|cannot distinguish if vaccine or wild-type, evaluate on epidemiologic grounds***|
|+ or -||+||distant history of measles||wild-type measles||may have few or no symptoms**, if clinically compatible may have been misdiagnosed initially|
* IgG response depends on timing of specimen collection (4)
** If so, do not consider contagious unless clinical presentation is consistent with measles
*** If IgM negative, helpful to rule out wild-type measles infection
- Cremer NE, CK Cossen, G Shell, J Diggs, D Gallo, and NJ Schmidt. (1985) Enzyme immunoassay vs plaque neutralization and other methods for determination of immune status to measles and varicella-zoster viruses and vs complement fixation for serodiagnosis of infections with those viruses. J. Clin. Microbiol. 21:869-873.
- Erdman DD, LJ Anderson, DR Adams, JA Stewart, LE Markowitz, and WJ Bellini. (1991) Evaluation of monoclonal antibody-based capture enzyme immunoassays for detection of specific antibodies to measles virus. J. Clin. Microbiol. 29:1466-1471.
- Hummel KB, DD Erdman, J Heath, and WJ Bellini. (1992) Baculovirus expression of the nucleoprotein gene of measles virus and utility of the recombinant protein in diagnostic enzyme immunoassays. J. Clin. Microbiol. 30:2874-2880.
- Helfand RF, JL Heath, LJ Anderson, EF Maes, D. Guris, and WJ Bellini. (1997) Diagnosis of measles with an IgM capture EIA: The optimal timing of specimen collection after rash onset. J. Infect. Dis. 175:195-199.
- Ratnam S, G Tipples, C Head, M Fauvel, M Fearon, and BJ Ward. (2000) Performance of indirect immunoglobulin M (IgM) serology tests and IgM capture assays for laboratory diagnosis of measles. J. Clin. Microbiol. 38:99-10.
This symbol means you are leaving the CDC.gov Web site. For more information, please see CDC's Exit Notification and Disclaimer policy.
Copyrighted images: Images on this website which are copyrighted were used with permission of the copyright holder and are not in the public domain. CDC has licensed these images for use in the materials provided on this website, and the materials in the form presented on this website may be used without seeking further permission. Any other use of copyrighted images requires permission from the copyright holder.