Secretory phospholipase A2 (sPLA2) during vaso-occlusive pain episodes (VOE) and acute chest syndrome (ACS) in sickle cell disease (SCD): Results from a prospective multi-center randomized controlled trial (RCT)

Abstract

Abstract Background: Acute chest syndrome (ACS) is the leading cause of morbidity and mortality in children with SCD, often developing during vaso-occlusive episodes (VOE) with minimal or no early clinical signs. Most children present with a normal lung exam, making prompt detection challenging. Secretory phospholipase A2 (sPLA2), a potent inflammatory mediator, has been shown to rise prior to ACS onset and may aid in predicting its development and severity in the acute setting. Objective: Assess sPLA2 as a marker for ACS risk and severity in patients with SCD hospitalized for VOE Methods: Cross-sectional analysis of data from a multicenter, double-blind, placebo-controlled, phase-3 RCT (NCT04839354) evaluating intravenous arginine therapy in patients aged 3–21 years with SCD-VOE conducted at 10 pediatric emergency departments (ED) in the US, endorsed by the Pediatric Emergency Care Applied Research Network (PECARN). Plasma sPLA2 levels at ED presentation, hospital day 2, and on the day of hospital discharge (DC) were analyzed via enzyme-linked immunosorbent assay (ELISA). sPLA2 level ≥48 ng/mL is considered elevated based on an established SCD-specific cutoff. ACS severity was classified as mild (no oxygen/transfusion), moderate (required oxygen/transfusion), or severe (required BIPAP, intubation, or PICU admission). Vital signs and clinical labs were analyzed. Results: Overall 271 patients were randomized, and 251 had sufficient blood samples for sPLA2 assessment at presentation and were included in the analysis (mean age 14±4 years; 53% male, 73% HbSS/Sβ°, and 75% on hydroxyurea). Mean plasma sPLA₂ level at ED presentation was 116±131 ng/mL, with elevated levels ≥48 ng/mL in 60% of patients with VOE. ACS was diagnosed in 21% of patients enrolled (n=52), with 18 diagnosed in the ED and 34 were later diagnosed with ACS during admission. Although the majority of ACS patients (85%) had a normal respiratory exam at ED presentation, 71% had elevated sPLA2 levels ≥48 ng/mL. Patients diagnosed with ACS at any point during enrollment (n=52) had significantly higher mean plasma sPLA2levels (n=52) at ED presentation compared to patients with no ACS (n=199) (152±147 vs 107±126 ng/mL, p=0.01). Moreover, patients with ACS exhibited significantly higher mean peak plasma sPLA2compared to subjects who never developed ACS (263±169 vs164±164 ng/mL respectively, p<0.001). The SCD-specific cutoff of sPLA2≥48 ng/mL yielded a sensitivity=85%, specificity=33%, NPV=89% and PPV=25% in predicting ACS. When comparing serial plasma sPLA2levels, mean sPLA2 at ED presentation was highest among patients presenting with ACS (198±182 ng/mL, n=18) with a positive chest x-ray (CXR) in the ED, followed by those with a negative CXR in ED who developed ACS during hospitalization (128±120 ng/mL, n=34). Notably, both groups demonstrated significantly higher sPLA2 levels at presentation compared to patients with No-ACS (106±125 ng/mL; p=0.02). This trend persisted throughout the hospital course, with mean sPLA2 levels continuing to rise by Day 2 and remaining significantly elevated at DC in both ACS groups compared to No-ACS (p<0.001). In the ACS cohort, 19 (36%) cases were classified as mild, 24 (46%) as moderate, and 9 (17%) were severe. Plasma sPLA2 levels at ED presentation increased with ACS severity, showing a stepwise rise from mild to moderate to severe cases. Subjects with severe ACS had a mean sPLA2 level that is 1.5-fold higher than those with mild disease (192±200 vs 122±140 ng/mL respectively) though not significant with the small sample size. A total of 16 patients presented to the ED with fever and 60 patients developed fever during their hospital stay (total n=76). Peak plasma sPLA2levels were significantly higher in febrile (n=76) versus afebrile (n=175) patients (254±19 vs 120±10 ng/mL, p<0.0001). ED plasma sPLA2levels correlated positively with several vital signs and clinical laboratory parameters including heart rate (r=0.42, p<0.001), respiratory rate (r=0.14, p=0.02), white blood cells (r= 0.48, p<0.001) and neutrophils (r=0.40, p<0.001). Moreover, sPLA2correlated negatively with lymphocytes (r=-0.42, p<0.001) and hemoglobin/hematocrit (r=-0.26, p<0.001). Conclusions: sPLA2 remains promising as a biomarker for ACS risk. We show it is also associated with ACS severity in children with SCD, supporting its potential role in acute clinical decision-making. Combined with other predictors, it may enhance early diagnosis and guide management.