Apparently non-specific results found using a norovirus antigen immunoassay for fecal specimens from neonates.

Norovirus is increasingly recognized as a frequent cause of non-bacterial gastroenteritis. Despite a 10-fold increase in the number of cases reported following the availability of enzyme immunoassays, there are no reports yet from preterm neonates. We report on a sudden clustering of antigen-positive enzyme immuno assays results in a level III neonatal intensive care unit, involving 22 of 43 infants screened. Although antigen-positive samples were significantly associated with bloody stools (P<0.001) and gastric residues (P<0.02), norovirus infection could not be confirmed by reverse-transcriptase polymerase chain reaction or electron microscopy. We question the validity of the so called norovirus-specific antigen assays and warn against overreacting to positive enzyme immunoassays results without reverse-transcriptase polymerase chain reaction confirmation especially in the neonatal setting.