Is activity restriction appropriate for patients with hereditary spherocytosis? A population-based analysis

Patients with hereditary spherocytosis (HS) are often thought to have an increased risk of blunt splenic injury (BSI) from trauma due to splenomegaly. We aim to quantify this risk. Using a population-based database consisting of all injury-related admissions in Canada from 2001 to 2010, we identified patients with BSI and HS based on the discharge diagnoses. Intercensal population estimates were used to derive rates of BSI. The HS population at risk for BSI was estimated based on population rates of HS obtained from the literature. Rates of BSI in the HS population were estimated and the relative rates of BSI were calculated to compare the populations with and without HS. There were 10,106 patients with BSI over 202,405,788 person-years of observation, yielding an overall rate of BSI in the general population of 5.0 BSI per 100,000 person-years. Of these BSI patients, only two had a history of HS. Population rates of HS in the literature range from 1 in 2,000 to 5,000, corresponding to a low estimate of 2.0 and a high estimate of 4.9 BSI per 100,000 person-years in the HS population. The relative rate of BSI in the population with HS compared to the population without HS ranged from a low of 0.4 (95 % CI 0.1-1.4) to a high of 1.0 (0.1-3.6). The rate of BSI in the HS patient population appears not to differ significantly from those in the general population.