From the Guidelines
The most likely laboratory test to indicate immunity to measles is the enzyme immunoassay (EIA) or enzyme-linked immunosorbent assay (ELISA), as these are more sensitive assays used in most laboratories, according to the CDC 1. When assessing immunity to measles, the goal is to detect the presence of measles-specific antibodies, which can be achieved through various serologic tests.
- The enzyme immunoassay (EIA) or enzyme-linked immunosorbent assay (ELISA) are considered more sensitive than the traditional hemagglutination-inhibition (HI) test, making them the preferred choice for determining immunity 1.
- A positive result from any serologic test, including EIA or ELISA, indicates that the person has measles-specific antibody and is considered immune.
- It is essential to note that individuals with an "equivocal" test result should be considered susceptible unless they have other evidence of measles immunity or subsequent testing indicates they are immune 1.
- In clinical practice, healthcare providers may order these tests for individuals with uncertain vaccination status, those who work in healthcare settings, or before international travel to areas with measles outbreaks.
- The CDC recommends confirming all new cases of suspected measles by laboratory testing, which may involve the use of EIA or ELISA to detect measles-specific antibodies 1.
From the Research
Laboratory Tests for Measles Immunity
According to the CDC, the following laboratory tests can indicate immunity to measles:
- Measles virus neutralizing antibody test, which measures the level of antibodies that can neutralize the measles virus 2
- Enzyme-linked immunosorbent assay (ELISA) for measles IgG antibodies, which detects the presence of IgG antibodies against the measles virus 3, 4, 5
- Plaque reduction neutralization test (PRNT), which is considered the gold standard for measuring measles antibody concentrations 5
Characteristics of Laboratory Tests
The characteristics of these laboratory tests are:
- Measles IgG ELISA: sensitive and specific, but may not be as accurate as PRNT 5
- PRNT: considered the gold standard, but may not be feasible for large-scale serosurveillance due to its complexity and cost 5
- Measles virus neutralizing antibody test: can measure the level of antibodies that can neutralize the measles virus, but may not be as widely available as ELISA 2
Diagnostic Accuracy of Laboratory Tests
The diagnostic accuracy of these laboratory tests varies:
- Measles IgG ELISA: pooled sensitivity and specificity of 91.6% and 96.0%, respectively 5
- PRNT: considered the gold standard, but its diagnostic accuracy may vary depending on the specific test and population being studied 5
- Measles virus neutralizing antibody test: can provide valuable information on the level of immunity to measles, but its diagnostic accuracy may vary depending on the specific test and population being studied 2