Introduction
In sickle cell disease (SCD), acute chest syndrome (ACS) is a major cause of significant mortality and morbidity. It is responsible for an estimated 25% of sickle cell disease-related deaths, and is associated with prolonged hospitalization, increased risk of respiratory failure, future lung disease and 25% mortality in hospitalized patients1,2. ACS has a 40% incidence in the SCD population and is most commonly caused by infection and pulmonary infarction. Pediatric patients with SCD frequently present to the pediatric emergency department (PED) with complaints of fever, chest pain, and cough, all of which may or may not be associated with ACS.
Other studies have been conducted to evaluate the differences between adult and pediatric sickle cell patients in their presentation of ACS. Findings include a lower prominence of extrapulmonary findings in pediatric patients as compared to adult patients. Factors such as low hemoglobin (Hb) and oxygen tension fraction were predictors of ACS in pediatric patients3. Madhi et. al., also noted that oxygen saturation (SpO2) level was significantly lower at admission for children with ACS when compared to adults.4 Certain co-morbidities, such as asthma, have been shown to increase risk of ACS in pediatric patients.5 Boyd et al. found that children with both asthma and SCD experienced almost twice as many ACS episodes vs. children with SCD without asthma.6 Other risk factors for ACS include young age, severe SCD genotypes, low fetal Hb levels, high steady-state Hb levels, high steady-state leukocyte count, history of asthma, and a previous history of ACS1.
Despite growing research in the field, it remains challenging for PED providers to determine which patients are at highest risk of ACS. In fact, a national hospital ambulatory medical care survey evaluated almost two-hundred thousand yearly emergency department (ED) visits by SCD patients from 1999-2007 and found that 37% of those aged 0-19 years ended up hospitalized7. This high frequency of ED visits and hospitalizations increased pediatric SCD patient exposure to nosocomial infections, radiation, and was associated with higher mortality.
Chest x-rays (CXR) are frequently ordered, increasing radiation exposure and healthcare costs. A Dallas Newborn cohort from 1996-2009 found that SCD patients had greater than 25 radiographic tests before age 18, and 5% of these patients had greater than 100 tests.8This is concerning since one CXR has an average effective radiation dose of 0.01-0.02 millisievert (mSv), comparable to 10 days of natural radiation exposure9,10. While there is currently no set limit on an acceptable radiation dose for pediatric patients, providers should make every effort possible to reduce unnecessary radiation exposure based on the principle of “as low as reasonably achievable” (ALARA).
Therefore, the objectives of this study were: 1) to identify incidence of CXR performance and ACS diagnosis in SCD patients, both with and without fever, presenting to our PED, and 2) to identify significant clinical and demographic predictors of ACS in this population in order to implement a diagnostic algorithm for PED providers with the goal of minimizing unnecessary CXR performance in this population.