Comparison of H1NI and Seasonal Flu Related Hospitalizations in Children with SCD: A Pediatric Health Information System (PHIS) Database Analysis

Influenza has a great health impact on children with sickle cell disease (SCD). One study reported greater rate of seasonal influenza-related hospitalizations in SCD compared to those with Cystic Fibrosis (CF). Another small study described excess morbidity in SCD due to 2009 H1N1 pandemic relative to prior seasons.

1. To examine time trends in influenza hospitalizations comparing 2009 H1N1 period with prior flu seasons, 2. To determine the relative impact of H1N1 pandemic in SCD in comparison to CF, 3. To determine the trend of antiviral use among hospitalized children with influenza.

We used the Pediatric Health Information System (PHIS), a database of clinical and financial data from free-standing children's hospitals in the US. Only patients under the age of 21 who were hospitalized at one of the 25 PHIS hospitals that provided discharge data from 1999–2010 were included in the analysis. Clinical outcomes of mortality, ICU admission, and mechanical ventilation as well as the use of antivirals were compared between patients hospitalized during the 2009–2010 H1N1 season and those hospitalized in prior influenza seasons. Categorical data were analyzed using χ² or Fischer's Exact tests and the Kruskal Wallis nonparametric test was used to analyze continuous data. A p-value of <0.05 was used to determine statistical significance.

Among hospitalized children with SCD, H1N1 accounted for a higher percentage of hospitalizations than did seasonal influenza (4.9% vs. 2.0%, P < 0.0001). Patients with H1N1 were older, had more acute chest syndrome and received more number of blood transfusions compared to patients with seasonal flu (p < 0.0001, Table 1). There were no differences in rates of mortality, ICU admissions, or mechanical ventilation between 2009 H1NI pandemic and seasonal flu in prior seasons. Influenza-related hospitalizations were higher among patients with SCD compared to patients with CF patients during both the H1N1 pandemic and prior seasonal epidemics (4.9% vs. 2.2% and 2.0% vs. 1.5%, respectively, P < 0.0001). However, there were no differences in mortality, ICU admissions or mechanical ventilation rates between these two groups during the H1N1 pandemic. In patients with SCD, rates of influenza testing were not different during H1N1 versus seasonal influenza (69% vs. 71%). Sickle cell patients were more likely to be tested than CF patients during seasonal influenza (71% vs. 56%, P <0.0001) but there was no difference in testing during the H1N1 pandemic (69% vs. 74%) indicating heightened awareness. Rates of antiviral therapy use in sickle cell patients hospitalized with influenza were dramatically higher during the H1NI pandemic compared to seasonal flu in prior seasons (85% vs. 34%, P < 0.0001). The same was demonstrated in CF patients (78% vs. 51%, P < 0.0001). This parallels the rise in the overall pediatric population noted (76% vs. 21%, P < 0.0001).

• Using the largest in-patient database, we report that H1N1 pandemic accounted for a greater percentage of hospitalizations among sickle cell patients compared to seasonal flu.

• We also confirm that sickle cell patients with H1N1 more often developed acute chest syndrome and required blood transfusions than seasonal influenza. However, there was no difference in mortality, ICU admissions, or rates of mechanical ventilation as previously suggested.

• We found that influenza-related hospitalizations in sickle cell patients is higher compared to CF patients, but severity of the hospital courses were comparable between the two groups during the H1N1 pandemic.

• Finally, use of antiviral therapy increased among hospitalized pediatric patients including those with SCD and CF during the H1N1 pandemic indicating a favorable response by physicians to clinical guidelines.

No relevant conflicts of interest to declare.