INTENDED USE

The Measles IgG/IgM Rapid Test Cassette is a lateral flow chromatographic immunoassay for the qualitative detection of IgG and IgM antibodies to Measles in serum or plasma to aid in the diagnosis of Measles infection.

SUMMARY

Measles (Rubeola) is a highly contagious viral disease resulting from infection with a paramyxovirus (genus Morbillivirus). Eight to twelve days following infection, a prodromal phase of measles begins, which is marked by fever, cough, coryza, and conjunctivitis. In many cases, the onset of the prodromal symptoms is followed (2 – 3 days) by the appearance of a specific enanthem (Koplik’s spots), and a generalized maculopapular eruption (3 – 4 days after onset). In uncomplicated measles, the appearance of the rash is followed by a peak in temperature one to two days later, and a rapid defervescence on the third or fourth day of the rash.

Under normal circumstances, the appearance of the prodromal symptoms, especially the highly specific and pathognomic Koplik’s spots, is sufficient for clinical diagnosis. However, since the introduction of the measles vaccine in 1963, the incidence of measles has dramatically decreased. As a result, medical professionals have had less experience in the clinical diagnosis of the disease and may require laboratory assistance for confirmation.

Diagnosis of measles can be further complicated by the appearance of an atypical form of measles in persons who were immunized with an inactivated measles vaccine between 1963 and 1967, and were subsequently reinfected with wild-type virus. The atypical form of measles may be severe and clinically confused with Rocky Mountain spotted fever. In addition, acute measles may be complicated by secondary bacterial infections of the respiratory tract and middle ear. Additional complications may include a post-infectious encephalitis and a rare, but often time fatal disease, subacute sclerosing panencephalitis (SSPE).

Antibodies to measles virus begin to appear with the development of the rash. A transient IgM antibody response (3 – 6 weeks) may appear first or in conjunction with IgG. IgG antibodies peak in 2 – 6 weeks, decline gradually over 6 months, and remain relatively stable thereafter. Following administration of live, attenuated measles vaccine, antibody can be detected 11 – 14 days after inoculation . Subclinical reinfections can occur in persons with either vaccine-induced or natural immunity resulting in a boost in measles-specific IgG titer.

In spite of the wide spread vaccination program, many individuals remain susceptible to measles as a result of primary vaccine failure or non-immunization. Serology is a useful tool for ascertaining the immune status of previously vaccinated individuals, and detection of seroconversion in recently vaccinated individuals. In addition, measles serology can be a valuable tool in the diagnosis of subacute sclerosing panencephalitis which may occur years after the original measles infection.

PRINCIPLES

The Measles IgG/IgM Rapid Test Cassette (Serum/Plasma) is a qualitative, lateral flow immunoassay for the detection of IgG and IgM antibodies to Measles in serum or plasma specimens. In this test, anti-human IgG and anti-human IgM are coated in the test line regions of the test. During testing, the serum or plasma specimen reacts with Measles antigen coated particles in the test strip. The mixture then migrates forward on the membrane by capillary action and reacts with the anti-human IgG and/or anti-human IgM on the membrane in the test line region. The presence of a colored line in the test line region indicates a positive result for Measles infection, while its absence indicates a negative result for that infection.
To serve as a procedural control, a colored line will always appear in the control line region of the strip indicating that proper volume of specimen has been added and membrane wicking has occurred.