Diagnostic performance of rectal swab versus bulk stool specimens for the detection of rotavirus and norovirus: implications for outbreak investigations.

backgroundIn January of 2008, during the peak of the rotavirus season in Guatemala, a gastroenteritis outbreak with high mortality among infants was reported in Guatemala. Despite extensive efforts, the investigation was limited by the lack of bulk stool specimens collected, particularly from the more severely dehydrated or deceased children.

objectivesWe evaluated the diagnostic performance of rectal swab specimens compared with bulk stool for the detection of rotavirus and norovirus. STUDY

designPatients with diarrhea (≥3 loose stools in 24 h) were enrolled through an ongoing surveillance system in Guatemala. From January through March 2009, we attempted to enroll 100 patients <5 years old captured by the diarrhea surveillance, and collected paired bulk stool and rectal swabs specimens from them. Specimens were tested for norovirus using real-time reverse transcription-polymerase chain reaction and for rotavirus via enzyme immunoassay.

resultsWe enrolled 102 patients with paired specimens; 91% of 100 paired specimens tested for rotavirus yielded concordant results positive for rotavirus with a negativity rate of 83%. Among 100 paired specimens tested for norovirus, 86% were concordant norovirus detection and the negativity rate was 85%. The diagnostic performance for rotavirus and norovirus detection did not differ significantly between the two specimen types.

conclusionsTesting of properly collected fecal specimens using rectal swabs may be a viable alternative to bulk stool for detection of rotavirus and norovirus, particularly during outbreaks where collection of bulk stool may be difficult.