Serum Biomarkers for Identifying Acute Chest Syndrome Among Patients Who Have Sickle Cell Disease and Present to the Emergency Department

Abstract

Objective. To compare the accuracy of biomarkers for identifying acute chest syndrome (ACS) in patients with sickle cell disease presenting to a pediatric emergency department (ED). Methods. We conducted a 13-month-long (2002–2003) cohort study with nested case-control in patients with sickle cell disease presenting to the pediatric ED with vaso-occlusive crises or fever in which we compared levels of secretory phospholipase A2 (sPLA2), endothelin-1, interleukin-6 (IL-6), and peripheral white blood cell count (WBC) in cases that were complicated by ACS and in control subjects with uncomplicated illnesses. For diagnosis, a test was considered to be accurate when the area under its receiver operator characteristic curve (AUC) was >0.70. Laboratory tests with AUC values ≥0.70 were entered into a binary recursive partitioning model for diagnosis. Results. For the period of study, samples from 72 visits were obtained from 51 patients who presented with vaso-occlusive crises (range: 1–4 visits per patient; 15 were enrolled more than once). ACS complicated 19 of 72 visits (26%, 95% confidence interval: 17%–38%). At an AUC value of 0.79, only the sPLA2 test was accurate for diagnosing ACS. AUC values for peripheral WBC, endothelin-1, and IL-6 were 0.68, 0.51, and 0.52, respectively. Binary recursive partitioning retained only sPLA2 at a cutoff of 13.7 ng/mL to be accurate for diagnosis. This cutoff had a sensitivity of 74% (14 of 19), a specificity of 87% (46 of 53), a positive likelihood ratio of 5.6, and a negative likelihood ratio of 0.18. Conclusions. Secretory phospholipase A2 but not endothelin-1, IL-6, or WBC is an accurate test for identifying present or incipient ACS in young patients who present to the ED with sickle cell pain crises.