Use of FTA® cards to transport throat swabs and oral fluid samples for molecular detection and genotyping of measles and rubella viruses.

The genetic characterization of measles viruses is an important tool for measles surveillance. Reverse cold chain requirements for the transportation of samples to reference laboratories are challenging in resource-limited settings. FTA® cards facilitate transport of virologic samples at ambient temperature as non-infectious material; however, the utility of FTA® cards for detection and genotyping of measles virus from clinical samples had not been evaluated. Throat swabs (TS) and oral fluid (OF) samples were collected from suspected measles cases in the Democratic Republic of the Congo. Virus detection (RT-qPCR) and genotyping (end-point RT-PCR) were compared for samples from 238 suspected cases; these samples were either transported using the reverse cold chain or at ambient temperature on FTA® cards. Virus detection showed excellent positive agreement for OF compared to TS (95.3%, CI [91.6, 97.4]), in contrast to 79.4% (CI 73.5, 84.3) for TS on FTA, and 85.5% (CI 80.2, 89.6) for OF on FTA compared to OF. Genotyping results obtained for a subset of samples indicated that 77.3% of all TS and 71.0% of OF would produce genotype information compared to 41.6% of TS and 41.3% of OF on FTA® cards. Similar results were found for 16 measles-negative samples that were confirmed as rubella cases. Measles genotype B3 and rubella genotype 2B were detected. FTA® cards have limited utility for virologic surveillance of sporadic cases of measles; however, they can be a useful tool for the expansion of virologic surveillance in countries where the reverse cold chain is not available.