Laboratory diagnosis of acute measles infections in hospitalized children in Zambia

In developing countries diagnosis of measles is generally made on the basis of clinical symptoms alone. In immunocompromised malnourished or vaccinated children measles presentation may be atypical which may impede accurate diagnosis. This study evaluated the capability of detection of immunoglobulin M (IgM) antibodies to confirm acute measles infection in 149 children hospitalized with measles in Lusaka Zambia. IgM antibodies were detected in 132 children (88.6%). The IgM-positive rate increased with time after the onset of skin rash and all 149 samples were positive by 4 days after admission. In addition virus isolations from throat swabs using B95a cells were performed but were positive in only 20.9% of cases. Both IgM and virus isolation in combination increased the detection rate to 92.5%. The 4 vaccinated children among IgM-negative children had high neutralizing antibody responses. These findings indicate that the IgM antibody test is a sensitive method for laboratory confirmation of measles infection in developing countries. It is recommended however that negative IgM tests be repeated after a few days.