Dr Leigh Martens

General Practitioner

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Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Measles


At a Glance

Why Get Tested?

To diagnose a measles or mumps infection; to establish whether a person has immunity to measles or mumps due to a previous infection or to vaccination; to confirm a measles or mumps case and investigate its source

When to Get Tested?

When a person has symptoms or complications that a health practitioner suspects are due to a measles or mumps infection; whenever it is necessary or desired to determine measles or mumps immunity; when an outbreak of measles or mumps is occurring in order to track and minimize it

Sample Required?

A blood sample drawn from a vein in your arm for measles or mumps antibody testing; to detect the virus itself, sample may be blood, urine, nasopharyngeal (nasal) aspirate/washing, throat swab, swab of the inside of the cheek (buccal swab), cerebrospinal fluid, or other body tissue

Test Preparation Needed?

Prior to collection of a buccal swab for mumps, the salivary gland located in front of and below the ear (parotid gland) is massaged. For other specimens, no test preparation is needed.

The Test Sample

What is being tested?

Measles (rubeola) and mumps are viruses that are members of the Paramyxoviridae family. They both cause infections that usually resolve within several days but can sometimes cause serious complications in certain cases. Both are preventable through vaccination. Measles and mumps testing may involve the detection of antibodies in the blood that develop in response to infection. Additionally, the virus or its genetic material (RNA) may be directly detected in a sample using culture or a molecular method such as polymerase chain reaction (PCR). These methods may be used for a variety of samples. (Read the "How is it used?" section for more testing details.)

The number of cases of measles and mumps infections has decreased from several hundred thousand a year in the U.S. to several hundred. The decreases are due to comprehensive measles and mumps vaccination programs. While vaccines are available for each virus, combination vaccines, such as MMR that protects simultaneously against measles, mumps, and rubella, are frequently utilized. In recent years, the majority of new cases in the U.S. have occurred in occasional outbreaks (epidemics), primarily in people who have not been vaccinated, especially those who have traveled to areas of the world where measles or mumps are more prevalent.

Measles, also called rubeola, is an extremely contagious viral infection that is transmitted through respiratory secretions. The virus infects cells in the lungs and at the back of the throat and, after a 1 to 2 week incubation, causes symptoms such as a high fever, dry cough, red eyes, light sensitivity, a runny nose, sore throat, tiny white spots inside the mouth, and a characteristic rash that typically starts on the face and spreads down the body to the trunk and legs.

Most people recover within a couple of weeks, but up to 20% develop complications that may include an ear infection, bronchitis, pneumonia, diarrhea, or more rarely encephalitis or blindness. People who are malnourished, have a vitamin A deficiency, or have compromised immune systems are frequently more severely affected. Women who are pregnant when they are infected with measles are at a greater risk of miscarriage or of premature labor.

Vaccination has drastically reduced the number of people affected by measles in the United States and in many parts of the world, but the World Health Organization (WHO) still lists measles as a leading cause of death in young children. According to their estimates, measles killed about 145,700 people globally in 2013, most of them children under the age of five.

The result of the vaccination efforts In the U.S. was the declaration in 2000 that endemic measles (measles continuously present in the population) had been eliminated. However, small outbreaks continue to occur on an annual basis. Most cases are occurring in those people who are either unvaccinated or have an unknown vaccination status, and most outbreaks are tied to travel to areas of the world where measles outbreaks are occurring.

According to the Centers for Disease Control and Prevention (CDC), during 2001-2011, 911 measles cases from 63 outbreaks were reported. In 2014, the U.S. had the highest number of measles cases reported in 20 years, with more than 600 cases. Many were linked to travelers who had visited the Philippines, where an exceptionally large outbreak of more than 50,000 cases occurred.

The CDC and the U.S. and global medical communities remain concerned and vigilant. Measles is still endemic in many areas of the world, there is always the risk of travelers spreading measles, and there continue to be small percentages of unvaccinated individuals (including children too young for vaccination).

Mumps is a viral infection that is transmitted through respiratory secretions or saliva. After a 2 to 3 week incubation period, an infected person typically develops flu-like symptoms such as a headache, muscle aches, and fever that are followed by characteristic parotitis – swelling of the salivary (parotid) glands below one or both ears. For most people, mumps is a mild, self-limited illness, but some may develop complications such as temporary or permanent deafness, inflammation of the testicles (orchitis) or ovaries (oophoritis), pancreatitis, meningitis, or encephalitis.

Mumps, a milder illness than measles, is much less common than it used to be but is still endemic in many parts of the world. According to the CDC, mumps cases in the U.S. range from about 200 to 2,000 a year. Outbreaks can occur in environments where people come in close contact, such as classrooms, sports teams, or in college dormitories. During 2011-2013, for example, several small outbreaks occurred on college campuses in California, Maryland, and Virginia, but their spread was very limited.

How is the sample collected for testing?

Antibody testing requires a blood sample, obtained by inserting a needle into a vein in the arm. Viral culturing or molecular testing may be performed on a variety of samples, including blood, urine, nasopharyngeal (nasal) aspirate/washing, throat swab, a swab of the inside of the cheek (buccal swab), cerebrospinal fluid, or other body tissue.

A nasopharyngeal swab is collected by having a person tip their head back and then a Dacron swab (like a long Q-tip with a small head) is gently inserted into one of their nostrils until resistance is met. It is left in place for several seconds, then rotated several times to collect cells, and withdrawn. This is not painful, but it may tickle a bit and cause the person's eyes to tear. For a nasal aspirate, a syringe is used to push a small amount of sterile saline into the nose and then gentle suction is applied to collect the resulting fluid.

In order to fully evaluate a suspected measles case, the CDC recommends the collection of blood as well as samples for culture and RT-PCR testing. For mumps, the CDC recommends the collection of blood and a buccal swab.

Is any test preparation needed to ensure the quality of the sample?

Prior to collection of a buccal swab for mumps, the salivary gland located in front of and below the ear (parotid gland) is massaged. For other specimens, no test preparation is needed.

The Test

How is it used?

Measles and mumps tests may be used to:

  • Confirm that a person is immune to the viruses due to previous infections or vaccination
  • Diagnose an active case of measles or mumps
  • Detect, monitor, and track outbreaks for public health purposes

(See the "What is being tested?" section for more about measles and mumps infections.)

A few different methods are available to test for measles or mumps:

Antibody testing (serology)
Antibody testing may be used to confirm immunity, diagnose an active case, or to track outbreaks. Measles and mumps antibodies are virus-specific proteins produced by the immune system in response to an infection by the measles or mumps virus, or in response to vaccination. There are two types of antibodies produced, IgM and IgG. The first type to appear in the blood after exposure or vaccination is IgM antibodies. Levels of IgM antibodies increase for several days to a maximum level and then begin to taper off over the next few weeks. IgG antibodies take a bit longer to develop, but once they do, they stay positive for life, providing protection against re-infection. Sometimes, testing of two blood samples obtained weeks apart (acute and convalescent) is used to differentiate between an active and prior infection by comparing the level of antibody in the two samples.

Direct detection of the virus
Direct detection may involve culturing the virus or molecular methods such as PCR and may be done on a variety of samples. These methods only identify active infections and cannot confirm immunity.

Viral genetic testing (RT-PCR) detects and identifies the genetic strain of the virus. Most RT-PCR testing is performed by public health laboratories and the Centers for Disease Control and Prevention (CDC).

Viral detection testing may occasionally be performed to identify the cause of severe complications that may be associated with an infection from the measles or mumps virus. Since people with weakened immune systems may not have a typical antibody response, a viral culture or a test to detect viral genetic material may be performed to confirm the diagnosis of a mumps or measles infection, especially if antibody results do not match clinical findings or a health practitioner's suspicions.

When is it ordered?

An IgG antibody test for measles or mumps may be ordered whenever a health practitioner wants to determine whether a person is immune to one or both of the viruses, either because of a previous infection or due to vaccination.

Measles or mumps IgM and IgG antibody tests, viral culture, or PCR may be ordered when a person has characteristic signs and symptoms of measles or mups or has had exposure to someone with the virus and now has a fever and some symptoms that could be due to measles or mumps. These tests are typically ordered early in the course of the infection.

Signs and symptoms of measles develop 7-18 days after exposure and usually include one or more of the following:

  • A characteristic rash that usually starts on the face and spreads down the body to the trunk and legs
  • High fever
  • Dry cough
  • Red, watery, itchy eyes
  • Sensitivity to light
  • A runny nose
  • Sore throat
  • Tiny white spots inside the mouth

Signs and symptoms of mumps typically develop after a 2 to 3 week incubation period and often resemble symptoms of the flu, such as:

  • Headache
  • Muscle aches
  • Fever
  • These are followed by characteristic swelling of the salivary glands below one or both ears called parotitis.

Testing may also be ordered during a suspected or confirmed outbreak, when several people may have been exposed and have the signs and symptoms listed above.

What does the test result mean?

Antibody testing
When measles or mumps IgM antibodies are present in someone who has not been recently vaccinated, then it is likely that the person has a current measles or mumps infection. When both IgM and IgG antibodies are present or there is a fourfold increase in concentrations between acute and convalescent IgG antibody tests, then it is likely that the person has a current or had a recent measles or mumps infection.

When measles or mumps IgG antibodies are present in a person who has been vaccinated and/or is not currently ill, then that person is protected against infection (immune). If a person does not have measles or mumps IgG antibodies, then that person is not considered immune to the viruses. This may be because the person has not been exposed to the viruses, because the IgG has not had time to be produced, or because the person does not have a normal antibody response.

The following table summarizes results that may be seen with antibody testing:

IgM IgG Possible Interpretation(s)
Positive Negative Early infection
Positive Positive (with increase in levels between acute and convalescent samples; this would only be done if the IgM test is not available) Current or recent infection
Negative Positive Immunity from prior infection or vaccination
Negative Negative No current or prior infection; not immune; no or low immune response due to compromised immune system

Viral isolation (detection)
A positive measles culture or mumps culture or a positive PCR test for the virus's genetic material means that the person has a current viral infection.

If a specific strain of measles or mumps virus is identified, then this genetic strain is the cause of the infection and the genetic information can be used to help determine the source of a measles or mumps infection, such as recent travel to a specific country or recent exposure to another person with an active infection. The result of measles or mumps genetic testing is used by the Centers for Disease Control and Prevention (CDC) to monitor the spread of the virus, to identify outbreaks, and prevent further transmission.

If the measles or mumps culture or PCR is negative, it may mean that the person is not infected and signs and symptoms are due to another cause. However, a negative result does not necessarily rule out an active infection because the virus may have been present in numbers too low to detect or may not have been present in the sample tested. If an infection is strongly suspected after a negative result, repeat or follow-up testing may be done.

Is there anything else I should know?

Most people recover from measles within a couple of weeks, but up to 20% develop complications that may include an ear infection, bronchitis, pneumonia, diarrhea, or more rarely encephalitis or blindness.

Mumps is most often a mild self-limited illness, but some people may develop complications such as deafness, inflammation of the testicles (orchitis) or ovaries (oophoritis), pancreatitis, meningitis, or encephalitis.

The measles, mumps, rubella (MMR) vaccine contains a live, attenuated (weakened) form of the viruses. Those with weakened immune systems and those who are pregnant or planning to become pregnant within the next month should not receive the vaccine. The initial dose of the vaccine is recommended for infants at 12-15 months of age and a second dose is given at 4-6 years of age.