Respiratory Tract Infections Due to Human Metapneumovirus in Immunocompromised Children

Chu, Helen Y.; Renaud, Christian; Ficken, Elle; Thomson, Blythe; Kuypers, Jane; Englund, Janet A.

In this retrospective study, we identified hMPV-infected immunocompromised children through screening of laboratory results from our virology laboratory. We did not screen asymptomatic children and may not have captured complete data on children who were evaluated solely as outpatients at other private clinics or hospitalized in other institutions. As the regional pediatric referral center, most immunocompromised patients are seen and followed at our institution but because of our large geographic referral area, it is possible that some children were seen elsewhere. Therefore, our study could be biased towards detection of more severe hMPV disease. Also, it is possible that a subset of earlier hMPV-positive cases were missed through use of DFA as compared to PCR, a more sensitive detection technique [12] . Furthermore, we were unable to capture all data at the time of clinical presentation, or to obtain full information regarding the clinical decisionmaking for the administration of ribavirin and/or IVIG. Therefore, the comparison of outcomes in patients who did and did not receive treatment is problematic, and the potential benefits of therapy are not readily evaluable. Unlike a previous hMPV study conducted in adult HSCT recipient patients in Italy [23] , we did not assess hMPV shedding in asymptomatic patients and unfortunately cannot comment on rates of symptomatic versus asymptomatic shedding of hMPV in our patients. Finally, we were limited in our ability to classify disease severity based on hypoxemia, as some patients did not have oxygen saturations charted. We suspect that a higher proportion of our patients would be classified as having severe disease using criteria such as that used by Papenburg et al [5] . Although only 8 (15%) of our patients were identified as having acquired their hMPV infection nosocomially, the vast majority of the patients were seen frequently on an outpatient basis in clinic for blood draws, interventions, and chemotherapy, making it difficult to differentiate true community-acquired disease from that acquired in the hospital setting.