Background: Human adenovirus (HAdV), especially species C (HAdV-C), can be detected incidentally by polymerase chain reaction in nasopharyngeal (NP) samples, making it difficult to interpret clinical significance of a positive result. We classified patients into groups based on HAdV culture positivity from respiratory specimens and the presence of an identified co-pathogen. We hypothesized that HAdV-C would be over-represented and viral burden would be lower in patients most likely to have incidental detection (ie, with a negative viral culture and documented co-pathogen).
Methods: Immunocompetent children with HAdV + nasopharyngeal specimens were classified into 4 groups: group I (HAdV culture (+) and no co-infection), group II (culture (+) and co-infection), group III (culture (-) and no co-infection) and group IV (culture (-) and co-infection). Viral burden (cycle threshold) and species were compared among groups.
Results: Of 483 nasopharyngeal specimens, HAdV was isolated in culture in 252 (52%); co-infection was found in 265 (55%) patients. Group I (most consistent with acute disease) had significantly lower cycle thresholds (median 23.9; interquarile range 22.2-28.1) compared with group IV (most consistent with incidental detection; median 37.3; interquarile range 35.3-38.9; P < 0.0001). HAdV-C accounted for 41% samples of group I and 83% of group IV (P < 0.0001). We identified a subset of 22 patients with bacterial or fungal co-pathogens, 18 of whom had no growth on viral culture (group IV) with a median cycle threshold of 37.4 (interquarile range 33.9-39.2).
Conclusions: Species identification and viral burden may assist in interpretation of a positive HAdV result. Low viral burden with HAdV-C may be consistent with incidental detection.