This test is used to diagnose rubeola infection (measles). It is more commonly used, today, to document immunity to infection by prior vaccination or clinical disease.
Rubeola is a RNA paramyxovirus that is known to cause the measles (not German measles—see Rubella). Upper respiratory symptoms, fever, conjunctivitis, a rash, and Koplik spots on the buccal mucosa highlight the disease. Since the 1970s, children have been vaccinated to prevent this disease. Although it is usually a selflimiting disease, the virus can easily be spread (by respiratory droplets) to nonimmune pregnant women and cause preterm delivery or spontaneous abortion.
Testing for rubeola includes indirect immunofluorescence serologic identification of IgG and IgM antibodies. The first represents a previous infection. The latter indicates an acute infection. A fourfold rise in IgM indicates a current infection.
This test is used to diagnose measles in patients with a rash or viral syndrome when the diagnosis cannot be made clinically. Even more importantly, however, this test is used to establish and document immunity (active—by previous measles infection, or passive—by previous vaccination). Populations commonly tested to document immunity include college students, health care workers, and pregnant women.
PROCEDURE AND PATIENT CARE
Explain the purpose of the test to the patient.
• Collect a venous blood sample in red-top tube.
• Apply pressure to the venipuncture site.
✪Inform the patient when to return for a follow-up rubeola titer if indicated.
✪If the results are negative for immunity, recommend immunization. For women of childbearing age, vaccination should precede future pregnancy.
TEST RESULTS AND CLINICAL SIGNIFICANCE
Active rubeola infection: These patients may not have the “classic” clinical signs of measles and diagnosis can be made with certainty through the identification of IgM antibodies in the patient’s serum.
Previous rubeola infection leading to immunity: These patients have IgG antibodies but do not have IgM antibodies. They are protected from the disease because of previous active infection or vaccination.
Rubella Antibody (p. 457). This test is used to diagnose German measles and to document immunity to the same.