Dried blood spots on filter paper as an alternative specimen for measles diagnostics: detection of measles immunoglobulin M antibody by a commercial enzyme immunoassay.

Background. We compared the results of a serum-based measles immunoglobulin M (IgM) test with results of tests using paired reconstituted dried filter paper blood spot (DBS) samples to assess the feasibility of using DBS samples for measles diagnostic procedures. Methods. We collected 588 paired serum and DBS samples from 349 children aged 8 months through 12 years at Mulago Hospital in Kampala, Uganda; of these samples, 513 (87%) were collected from children with a clinical diagnosis of measles 0-33 days after rash, and 75(13%) were collected from children hospitalized for other reasons. Eluted DBS and serum samples were tested using a commercial measles IgM enzyme immunoassay. Detection of viral RNA was attempted on a subset of 20 DBS by reverse-transcriptase polymerase chain reaction. Results. Among the 513 sample pairs collected from children with measles, the concordances for samples collected during days 0-6 and >1 week after rash were 95.7% and 100%, respectively (P < .01). The relative sensitivity and specificity of the DBS-based assay during the first week were 98.7% and 88.9%, respectively, and the sensitivity and specificity >1 week after rash were 100% and 100%, respectively. Viral RNA was detected in 5 (26%) of 19 DBS samples tested. Among 75 sample pairs collected from children hospitalized for other reasons, concordance was 94.7%. Conclusions. DBS samples are a feasible alternative sample for measles diagnostic procedures in high-incidence settings.