DETECTION OF RUBELLA VIRUS RNA IN DRIED BLOOD SPOT AND SERUM SPECIMENS

To study the presence of rubella RNA in specimens derived from blood, real-time RT-PCR was used to test rubella RNA in dried blood spot (DBS) and serum specimens collected during a large outbreak in Peru during 2004-2005. DBS, serum, and oral fluid specimens were collected from patients with clinical diagnosis of rubella. Control specimens were collected from healthy blood donors at the same time period in Peru.

All oral fluid specimens were tested first by conventional RT-PCR. For the samples collected from oral fluid conventional RT-PCR positive patients, 14 of 85 DBS and 13 of 50 serum specimens were positive by real-time RT- PCR; 24% (11/45) DBS and 34% (11/32) serum specimens collected on day 0-1 after rash onset were positive; 9% (3/31) DBS and 13% (2/15) serum specimens collected on day 2-4 were positive; none of the 9 DBS or 3 serum samples collected on day 5 or later were positive. All the 49 DBS, 23 serum specimens from blood donors and 58 DBS, 20 serum specimens from oral fluid conventional RT-PCR negative patients were real-time RT-PCR negative. 

Sequences for 7 of the 14 positive DBS samples and 2 of the 4 positive sera were obtained using the RNA extracted from the DBS or serum samples and found to be genotype 1C, the same genotype as the oral fluid samples from the same outbreak.

Detection of rubella RNA from DBS and serum is probably not ideal for laboratory confirmation. Successful genotyping of rubella virus from RNA extracted from DBS and serum specimens demonstrates that both types of specimens can be used for rubella molecular epidemiology analysis especially when oral fluid specimens are not available.