Measles seroconfirmation using dried capillary blood specimens in filter paper.

Because the incidence of measles has declined in recent years, the potential for confusion of measles with other morbilliform rashes has increased. Routine serologic testing of suspected cases of measles is recommended but it has been hampered, particularly in young infants and children, by the requirement of performing venipuncture. We have compared measles hemagglutination inhibition antibody testing performed on dried capillary whole blood collected on filter paper strips with testing of serum specimens obtained simultaneously by venipuncture. We assessed overall comparability, diagnostic sensitivity and specificity and acceptability and practicality for field use. Of the 125 capillary-venous sets compared, there was a 4-fold difference in hemagglutination inhibition titer between the two types of specimens in only one set (0.8%). Diagnostic sensitivity using capillary blood was 100% and specificity was 96%. Immunoglobulin M assessments on six capillary-venous sets were in complete agreement (three positive in both, three negative in both). In a pilot program of field use, filter paper blood collection was associated with a 97% (36 of 37) success rate in obtaining specimens from individuals with suspected cases of measles. This method of blood collection and testing is an accurate, feasible and acceptable means for seroconfirmation of measles.