Test ID: MMPGM    
Mumps Virus Antibody, IgM and IgG (Separate Determinations), Serum

Diagnosis of mumps virus infection

Determination of postimmunization immune response of individuals to the mumps vaccine

Documentation of previous infection with mumps virus in an individual with no previous record of immunization to mumps virus

The mumps virus is a member of the Paramyxoviridae family of viruses, which include parainfluenza virus serotypes 1-4, measles, respiratory syncytial virus, and metapneumovirus. Mumps is highly infectious among unvaccinated individuals and is typically transmitted through inhalation of infected respiratory droplets or secretions. Following an approximately 2-week incubation period, symptom onset is typically acute with a prodrome of low-grade fever, headache, and malaise.(1,2) Painful enlargement of the salivary glands, the hallmark of mumps, occurs in approximately 60% to 70% of infections and in 95% of patients with symptoms. Testicular pain (orchitis) occurs in approximately 15% to 30% of postpubertal men and abdominal pain (oophoritis) is found in 5% of postpubertal women.(1) Other complications include mumps-associated pancreatitis (<5% of cases) and central nervous system disease (meningitis <10% and encephalitis <1%).

Widespread routine immunization of infants with attenuated mumps virus has dramatically decreased the number of reported mumps cases in the United States. However, outbreaks continue to occur, indicating persistence of the virus in the general population.

Laboratory diagnosis of mumps is typically accomplished by detection of IgM- and IgG-class antibodies to the mumps virus. However, due to the widespread mumps vaccination program, in clinically suspected cases of acute mumps infection, serologic testing should be supplemented with virus isolation in culture or detection of viral nucleic acid by PCR in throat, saliva, or urine specimens.

IgM:

Negative

Index value 0.00-0.79 =negative

Reference values apply to all ages.

IgG:

Vaccinated: Positive (> or =1.1 AI)

Unvaccinated: Negative (< or =0.8 AI)

Reference values apply to all ages.

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 drawn 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.

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.

IgM:

The SeraQuest mumps IgM kit showed a sensitivity of 97.3% and a specificity of 96.6% when 160 specimens were tested in parallel with a reference method.(Package insert: SeraQuest, North Miami, FL)

IgG:

To evaluate the accuracy of the BioPlex Mumps IgG multiplex flow immunoassay (MFI), 500 prospective serum specimens were analyzed in a blinded fashion by the SeraQuest Mumps IgG EIA and the BioPlex Mumps IgG assay. Specimens with discordant results after initial testing were repeated by both assays during the same freeze/thaw cycle. Further discrepancies were evaluated by the Mumps IgG VIDAS enzyme-linked fluorescent immunoassay (ELFA; bioMerieux, Inc). The results are summarized below:

(a) All 4 of these samples tested positive by VIDAS Mumps IgG ELFA

(b) One of these 3 samples tested negative by the VIDAS Mumps IgG ELFA

Sensitivity: 98.1% (412/420); 95% Confidence Intervals (CI): 96.2%-99.1%

Specificity: 82.8% (48/58); 95% CI: 70.9%-90.6%

Overall Percent Agreement: 94.2% (471/500); 95% CI: 91.8%-96.0%

1. Hviid A, Rubin S, Muhlemann K: Mumps. Lancet 2008 Mar;371(9616):932-944

2. Hodinka RL, Moshal KL: Childhood infections. In Essentials of Diagnostic Virology. Edited by GA Storch. Churchill Livingstone, New York, 2000, pp 168-178