Mumps laboratory tests

Overview
Laboratory testing for mumps virus can be useful, and may include virus isolation from swabs of affected salivary ducts, antigen detection by PCR, and serologic testing for IgM antibody or a significant rise in IgG antibody. However, there are many important caveats to be aware of when interpreting the results.

Complete blood count with differential:

 * Total WBC count may be normal to elevated
 * Relative lymphocytosis may be observed

Serum studies:

 * Elevated of serum amylase secondary to the involvment of parotid gland and suspected pancreatitis associated with mumps


 * Elevated serum lipase secondary to pancreatitis


 * Elevated C-reactive protein may be seen secondary to orchitis

Serology

 * Significant rise in IgG or IgM antibodies may be helpful to confirm the diagnosis.


 * However, laboratory confirmation of mumps in previously vaccinated or previously infected individuals is challenging, and failure to detect mumps IgM in previously vaccinated persons has been well documented including the cross reactivity of mumps and parainfluenza viruses.


 * Persons with a history of mumps vaccination may not have detectable mumps IgM antibody regardless of timing of specimen collection.CDC


 * The ability to detect IgM varies by vaccination status and is:
 * highest in unvaccinated persons (80%–100%),


 * intermediate in one-dose vaccine recipients (60%–80%),


 * lowest in two-dose vaccine recipients (13%–14%)

Virus Isolation

 * Infected patients remain contagious approximately 6 days before the onset of parotitis until about 9 days after the onset of parotitis, during which time the virus can be isolated.


 * Virus can be isolated in a cell culture inoculated with the virus obtained from swabs of affected salivary ducts, serum or urine.


 * Antigen detection by polymerase chain reaction (PCR) is reserved for patients with secondary CNS infection.