Request form must state which investigation is required, immune status (IgG) or query Infection ( IgG & IgM). Full clinical details, including date of onset, will ensure the correct tests are performed.
Paired sera should be obtained wherever possible:
(a) acute sample - as early as possible in the illness, and
(b) convalescent sample 2 - 3 weeks after onset.
IgG testing is performed 2 - 3 times a week. IgM testing is performed once a week (unless there is a disease outbreak)
The IgM assay is not intended for the determination of immune status.
Absence of detectable IgM does not rule out the possibility of recent or current infection.
IgM in the neonate's serum can be considered indicative of congenital infection only if there has not been placental leakage.
Mumps is a systemic disease characterised by swelling of the salivary glands. Approximately one third of infections are subclinical. Meningeal signs are common. Encephalitis occurs rarely, and permanent sequelae or death is uncommon. Orchitis is a common complication after puberty but sterility rarely occurs. Other rare complications include arthritis, renal impairment, thyroiditis, mastitis, pancreatitis and hearing impairment.
Infection during the first trimester can increase the rate of spontaneous abortion and although mumps virus can cross the placenta, no evidence exists that it causes congenital malformations.
Infections are common in late winter and spring. Transmission is by direct contact via the respiratory route. Mumps is usually a childhood disease. If contracted in adulthood, severity (including orchitis) increases. The incubation period is usually 16-18 days but cases may occur 12-25 days after exposure. The greatest period of communicability is about 7 days before and after the onset of parotitis.
Widespread use of MMR vaccine has reduced the incidence of mumps, but outbreaks can still occur even in highly vaccinated populations, indicating that mumps transmission can be sustained among the few persons not protected by vaccination.
Laboratory diagnosis is either by viral isolation or serology. It is unknown what the timing relationship between symptom expression and IgM production is, although it is probably in the order of 7-12 days after symptom onset. Use of ELISA IgM and IgG assays in parallel (particularly if acute and convalescent sera are collected) allows for greater confidence in diagnosis of mumps infection by serology when viral isolation procedures are not available.
References
1. Trinity Biotech Mumps IgM ELISA kit insert.
2. 1997 Red Book. Report of the Committee on Infectious Diseases 24th Edition. Published by American Academy of Paediatrics p (i-xxvi) and (1-764) 1997.
For further information contact the laboratory (contact via Lablink: 22000 or (09) 307-8995 or 0800 522 7587) ,or:
the Virology team
virology@adhb.govt.nz