NOTES Dried Blood Spots versus Sera for Detection of Rubella Virus-Specific Immunoglobulin M (IgM) and IgG in Samples Collected during a Rubella Outbreak in Peru of rubella virus-specific IgM and IgG results for serum/DBS sample pairs for persons with sus

Most persons with rubella virus-specific immunoglobulin M (IgM)-or IgG-positive sera tested positive (98% [n ‫؍‬ 178] and 99% [n ‫؍‬ 221], respectively) using paired filter paper dried blood spot (DBS) samples, provided that DBS indeterminate results were called positive. For persons with IgM-or IgG-negative sera, 97% and 98%, respectively, were negative using DBS. Simplification of specimen collection, storage, transport, and processing in the field would be a great advantage to rubella surveillance. Recent studies have suggested that filter paper dried blood spots (DBS) are suitable for laboratory detection of measles-specific immunoglobulin M (IgM) The presence of rubella virus-specific IgM in serum according to enzyme immunoassay is diagnostic for rubella, and thus, results from sera were used as the standard. However, because most specimens were collected in the first week after rash onset, a time period when serum IgM and IgG enzyme immunoassays do not detect many rubella cases, we do not refer to serum samples as a "gold standard" (1, 9). Health care workers at the local health care centers in five Regional Health Directorates in Peru enrolled persons 8 months or more in age seen within 28 days of rash and fever onset (clinically suspected rubella). Persons who were vacci-* Corresponding author. Mailing address: Centers for Disease Control and Prevention