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

ABSTRACT

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.