Asplenic patients and invasive pneumococcal disease-how bad is it these days?

OBJECTIVES: Most are aware of pneumococcal infection as a complication of splenectomy and the increased risk of severe invasive pneumococcal disease (IPD) in asplenic patients. However little is known of the current status of this entity in a population with an active pneumococcal conjugate vaccine program for children.

METHODS: All IPD cases reported from 2000 to 2014 in Northern Alberta, Canada were collected prospectively. Socio-demographic variables, clinical characteristics, and IPD-related outcomes were compared between patients with and without a spleen using the Student t-test, Chi-square test, or Fisher's exact test, as appropriate.

RESULTS: Thirty-seven of 2435 patients with IPD (1.5%) were asplenic. Asplenic patients were significantly more likely to require mechanical ventilation or admission to the intensive care unit and had more complications (e.g., acute kidney injury). However, in-hospital mortality rates were similar in those with and without a spleen (19% vs. 16%, p=0.58). Pneumococcal serotype 22B was 33-fold higher in asplenic patients compared to those with a spleen.

CONCLUSIONS: In patients with IPD, those who are asplenic have a more severe infection than those with a spleen; however, the mortality rate is not significantly different. The reason for the predominance of serotype 22B requires further investigation and if replicated may warrant attention to current vaccination strategies.