Introduction Hyperinflammatory response induced by the SARS-CoV19 (CV) coronavirus is the main cause of morbidity and mortality. Numerous studies have pointed-out the main role of monocyte activation. In addition neutrophils alterations appear to differ pathophysiologically from the changes that occur in Influenza Virus (IV) infection. Due to the overlap of symptoms between these two entities, the search of analytical markers that help in early diagnostic orientation is considered of crucial importance. Changes in cell function, phenotype, and morphology in circulating leukocytes can be translated into numerical data obtained from an automated analyzer. The objective of our study is to generate an Artificial Intelligence Model from conventional hematological blood count parameters which be able to discriminate between CV and IV infection, in a fast and efficient maner. Methods This is a retrospective single-center study, performed between January-April 2020. The patients (n = 816) were divided into two groups: Patients who came for suspected COVID and had a positive RT-PCR (n = 408) and patients with a diagnosis of influenza confirmed by RT-PCR (n = 408). The database was divided into two random subgroups (n = 654) to train the model and another (n = 162) to validate it. The first hemogram on admission to the Emergency Department of these patients was performed on a Beckman-Coulter® DXH-900 equipment. Total white blood cells, absolute neutrophils, absolute lymphocytes, absolute monocytes, monocyte distribution wide (MDW) and Cell Morphological Data (CMDs) based on the impedance, conductivity and light scattering of these leukocyte subpopulations have been used to construct the model. Five algorithms have been evaluated using the R studio Software and the Caret (Classification and Regression Training) package: Linear Discriminant Analysis (LDA), K-Nearest Neighbor (kNN), Neural Networks (NN), Support Vector Machines (SVM) and Recursive partitioning (Rpart). Results The evaluation of the different models was based on the comparison of the efficacy obtained through a cross validation (10x). It was decided to choose the SVM model by presenting a median of the area under the ROC curve of 0,841. No data preprocessing was performed, and the parameters chosen for the model were: sigma = 0,014, C = 1 and Number of Support Vectors = 458. Parameters with greater importance (>80%) in the model, were CMDs based on Neutrophil Light Scattering (SDLNE, SDLAN, SDMNE and MNLNE). The analysis of results was performed using a confusion matrix, where the model predicts the diagnosis of each patient in the validation subgroup (Table 2). A ROC curve with an area of 0,892 was obtained, with a sensitivity and specificity of 80% and 85%, respectively (Fig 1). Conclusions The creation of prediction algorithms from hemogram parameters allow to discriminate between COVID 19 infection and influenza A and B with a high specificity and sensitivity in a fast way. This could be a great advance for the early diagnostic orientation and guide clinical decisions as soon as possible with the consequent clinical benefit. Disclosures No relevant conflicts of interest to declare.

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e13638 Background: Rituximab (anti-CD20 Ab) is the cornerstone of the treatment of non-Hodgkin B lymphomas. Infusion-related reactions (IRR) are the most common adverse effects. To reduce them, intravenous premedication with antihistamine and acetaminophen is administered prior to rituximab. If no IRR after first infusion, subsequent infusions time takes 3-6 hours. Many centers use the rapid 90-minute infusion (off-label). Since 2017 subcutaneous rituximab formulation is available, that takes 5 minutes of administration. Nevertheless, in order to reduce cost, due to approval of biosimilars, some health providers continue using intravenous rituximab. On the other hand, with COVID pandemic, an effort to reduce visits and day-care hospitals stays has been made. In the current situation, it would be convenient to reduce day-care stay and the nursing care burden. We wanted to evaluate the safety of an ultrarapid infusion of biosimilar rituximab in a total time of 30 minutes by analyzing IRR and adverse events (AE). Methods: Since November 2021, 3 cohorts of ultrafast infusion have been studied as follows: One cohort (Cohort 1) with intravenous premedication with dexchlorpheniramine and acetaminophen, followed by rituximab infusion over 1 hour, and 2 cohorts with rituximab infusion over 30 minutes: Cohort 2: with intravenous premedication, and cohort 3 with oral premedication. IRR and adverse events have been independently reviewed and graded using Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0 (November 27, 2017). Results: 34 patients have been included receiving 48 rituximab infusions (16 infusions in each cohort). Median age was 64 years old (range: 51-91). Diagnostic of NHL were as follows: large b cell: 10; follicular: 13; marginal: 7; mantle cell: 1, Waldeström: 1; Ritcher transformation: 2. Rituximab infusion was in monotherapy (21), and in combination (27) with: bendamustine: 9, CHOP: 17, GEMOX: 1. Considering safety, no IRR has been observed in cohort 1 (1 hour infusion), and 1 IRR grade II in cohort 3 (30 minutes, oral premedication). Other AE were: hypertension grade I and hypotension grade I, both in cohort 2. Conclusions: Ultrarapid rituximab infusion is safe. Oral premedication is feasibly allowing a total infusion time of 30 minutes. This infusion rate alleviates day-care burden saving between 75-90% of time in each rituximab infusion, reduce day-care stay and is comfortable for the patients. Clinical trial information: NCT05191225.