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Laboratory Testing for Suspect Measles Cases April 10,
2008
Diagnosis of Measles
A diagnosis of measles should be considered in any person with a
generalized maculopapular rash, fever and cough, coryza and/or
conjunctivitis. Laboratory diagnosis of measles is required for all
sporadic (non-outbreak related) cases.
Because previously indigenous measles had been eliminated in Canada
and now Ontario is having an outbreak, laboratory testing of suspect measles cases
must include both serology and virus
isolation/detection.
Initial lab testing:
- a) Acute Serology: A blood specimen, to test for
measles antibodies (IgM and IgG) at the first visit and ideally
obtained on day 4 or within 7 days after rash onset.
- b) Virus isolation/detection: A nasopharyngeal
swab or aspirate, or a throat swab obtained within 4 to 7 days after
the onset of rash, and /or approximately 50 ml of urine within 7
days after the onset of rash.
Follow-up lab testing:
- a) Convalescent serology: A second blood
specimen drawn >10 to 20 days after the first to check for
seroconversion or a significant rise in measles specific IgG
antibodies between acute and convalescent sera. Seroconversion
or a significant rise in IgG titre is indicative of recent
infection.
Note: If the acute (initial) serology results
in a person with clinical symptoms of measles and known or
suspected exposure to measles show low, indeterminate or
negative IgM and IgG, both tests should be repeated in one to
two weeks.
When requesting measles specific IgM and IgG testing, please
provide relevant clinical information on the lab requisition
form and the purpose of the testing i.e. suspect measles, recent
vaccination history and recent travel history.
Expected Time to Receive Results
o A few days for blood test results.
o Up to a week for PCR results.
Note: Please ensure that your local public health unit is aware
of all individuals who are being tested for measles.
References
1 Bellini WJ, Icenogle JP. Measles
and rubella viruses. In Murray PR, Editor. Manual of Clinical
Microbiology, 8th Edition. ASM Press, Washington, D.C.; 2003.
2 Heymann DL, editor. Control of Communicable
Diseases Manual, 18th edition. American Public Health *
Association. Washington, D.C.; 2004. |
Measles