1185 Introduction: Patients with thalassemia major require RBC components that retain sufficient viability to correct anemia and suppress endogenous erythropoiesis. For novel RBC products prepared with pathogen and leukocyte inactivation (PI) it is also important to meet these goals while having minimal effect on transfused iron burden. Unfortunately, ideal endpoints for the efficacy of RBC transfusion in this patient population have not been extensively defined, and published data characterizing relevant statistical parameters are limited. We studied the statistical properties of three transfusion efficacy endpoints in a sample of thalassemia major patients receiving conventional RBC components. The variability of these parameters is a key consideration in the design of clinical trials assessing RBC transfusion efficacy. Methods: Data from 6 transfusion cycles for adult subjects with thalassemia major were randomly extracted from Webthal, a computerized clinical record for thalassemia patients in use at Italian Thalassemia Centers. Only subjects who received all RBC components during a single transfusion episode for each cycle were included in the analysis. Three potential transfusion endpoints were investigated: (1) cumulative hemoglobin (Hb) use (g/kg/day), (2) 1-h post-transfusion Hb increment (g/dL), and (3) proportional Hb decline per day following transfusion (%/day). Data for Hb increment and Hb consumption were based on volume of RBC components adjusted to a hematocrit of 100%. Cumulative Hb consumption provides a summary assessment of transfusion efficacy and iron burden over the 6 transfusion cycles. For the longitudinal endpoints (2) and (3), mixed effects longitudinal models were used to assess whether these endpoints significantly differed across the 6 transfusion cycles. Results: When subjects were selected for consistency of transfusion cycles, and all RBC components for a cycle were administered in a single transfusion episode, a relatively homogeneous population may be defined. In this instance, all of the longitudinal outcome measures were consistent and variability in the measures over 6 transfusion cycles was limited. For 18 subjects over 6 transfusion cycles, the mean cumulative Hb consumption was 0.11 g/kg/day (SD=0.033). Values for each endpoint are presented for each cycle (Table). Conclusions: Based on this analysis, a combination of endpoints related to RBC transfusion for support of thalassemia major can be defined to describe comprehensively the efficacy of novel RBC components. The endpoints presented are clinically relevant to routine care, and thus unlikely to result in missing data. None of the longitudinal endpoints demonstrated substantial differences across the 6 transfusion cycles for patients on a stable transfusion regimen. Thus, these endpoints provide relevant comparative parameters for novel RBC components such as PI RBC. Their limited variability is beneficial for non-inferiority clinical trials. Furthermore, inter-subject variability is much greater than intra-subject variability. A crossover design would further enhance the clinical trial such that a feasible number of subjects may be enrolled to achieve 80–90% power to reject inferiority. Disclosures: Reed: Cerus Corporation: Employment, Stock and stock options Other. Sherman:Cerus Corporation: Employment, stock and stock options Other. Corash:Cerus Corporation: Employment, stock and stock options Other.

An 11-month-old boy presented to the pediatric emergency department (PED) of a spoke hospital after a 1-day history of fussiness, inconsolable crying, and two vomits. Upon admission, he appeared alert, yet pale and fussy. Physical examination revealed mild abdominal tenderness and a palpable mass in the left lower quadrant. A few hours later, drowsiness and oral intake refusal appeared. The laboratory test results were normal. A chest X-ray (CXR) revealed a left lower consolidation with possible effusion (Fig. 1,a). Moreover, abdominal ultrasound showed a large gastric shadow and dilated small intestinal loops with hydro-air levels.Upon admission, the patient, who had been promptly referred to our tertiary care PED, was in a good clinical condition and had no pathological findings on pulmonary auscultation. A lung point-of-care ultrasound (LUS) conducted by an emergency pediatrician, using a high frequency (7e15 MHz) linear transducer, with the patient placed in both the supine and sitting positions to scan all the chest walls, revealed a bowel with active peristalsis in the left emithorax as well as partial absence of the part of the affected hemidiaphragm and partial absence of the pleural line; therefore, the most likely diagnosis was congenital diaphragmatic hernia (CDH) (Fig. 1,b).Computed tomography (CT) scan (Fig. 1,c) and explorative laparotomy were performed. The left CDH was confirmed and mainly repaired during surgery. The postoperative period was uneventful and the patient was discharged from the hospital 8 days later.