Serum specimens obtained during the acute phase of infection or soon after vaccination may be negative for IgM- or IgG-class antibodies by serological tests.
All positive IgM results must be interpreted cautiously as some false-positive results or heterotypical responses of the IgM have been seen in the serum of pregnant women or in patients with an acute infection caused by cytomegalovirus, herpes simplex virus, measles, rubella, or parvovirus.
Testing for IgM-class antibodies to mumps virus should be limited to patients with a clinically compatible disease.
Mumps virus shares antigenic relationships with other viruses of the paramyxovirus group; therefore serologic cross-reactions are possible, but uncommon with this test procedure.
IgG-class antibodies to mumps virus may be present in serum specimens from individuals who have received blood products within the past several months, but have not been immunized or experienced past infection with this virus.
Index value 0.00-0.79 =negative
Reference values apply to all ages.
Vaccinated: Positive (> or =1.1 AI)
Unvaccinated: Negative (< or =0.8 AI)
A positive IgG result coupled with a positive IgM result suggests recent infection with mumps virus. This result should not be used alone to diagnose mumps infection and should be interpreted in the context of clinical presentation.
A positive IgG result coupled with a negative IgM result indicates previous vaccination to or infection with mumps virus. These individuals are considered to have protective immunity to reinfection.
A negative IgG result coupled with a negative IgM result indicates the absence of prior exposure to mumps virus and nonimmunity. However, a negative result does not rule-out mumps infection or response to vaccination. The specimen may have been collected before the appearance of detectable antibodies. Negative results in suspected early mumps infection or within a week following vaccination should be followed by testing a new serum specimen in 2 to 3 weeks.
Equivocal results should be followed up with testing of a new serum specimen within 10 to 14 days.