Preoperative monocytosis is predictable at diagnosis for RT-PCR negative COVID-19 paediatric cardiac surgery patients.

Other markers investigated in this population have gained importance in the diagnosis of the disease since the course of COVID-19 disease is atypical in the paediatric population and PCR may be misleading. The leukocyte profile is one of these biochemical tests. Children did not have lymphopenia in hemogram count, whereas relatively neutropenia and monocytosis were detected, unlike the adult population. The reason why children do not have lymphopenia is thought to be due to the fact that the thymus is more active in the first years of life.Two-hundred and four patients operated in our paediatric cardiac surgery clinic from 11March, 2020 to 1 April, 2021 were retrospectively examined and 11 patients with preoperative asymptomatic and PCR (-), but with PCR (+) in the post-operative period (patients with incubation period or false PCR negativity) were included in our study. Patients requiring emergency operation and operated from PCR (+) patients in the preoperative period were excluded from the study.The neutrophil ratio in the lymphocytic series of 7 patients out of 11 patients was slightly below the normal range in the preoperative period, the lymphocyte ratio of 3 patients was slightly above the normal range, and the relative monocyte ratio of 10 patients was slightly above the normal range.We think that evaluating the leukocyte profile combined with RT-PCR will give more accurate results in the diagnosis of incubation period and false RT-PCR negative patients. In addition, we believe that the algorithms for non-complex paediatric cardiac surgery procedures and timing in the paediatric population with a better course of COVID-19 disease with a positive post-operative course.

THE REACTION OF AIRLINE STOCKS IN EUROPE TO THE COVID-19 PANDEMIC: AN EVENT STUDY METHODOLOGY1

COVID-19 salgını tüm yaşamı, küresel ekonomiyi ve finans piyasalarını olumsuz etkiledi. Avrupa'da ve dünyanın birçok bölgesindeki çoğu işletmeyi olumsuz etkilediği gibi havayolu taşımacılığını da belirli bir süre durdurdu. Bu süreçte doğal olarak borsalarda aşırı kayıplar yaşandı. Bu durumdan en çok etkilenenler arasında havayolu pay senetleri de bulunuyordu. Bu açıdan bakıldığında, çalışma 14 Avrupa ülkesinin borsalarında işlem gören 38 havayolu hissesini "olay çalışması metodolojisi" ile analiz etmektedir. Temel amaç, bu ülkelerin borsalarında işlem gören havayolu hisse senetlerinin pandemiye tepkisini karşılaştırmak ve bunların istatistiksel olarak anlamlı kümülatif ortalama anormal getiri sağlayıp sağlamadığını belirlemektir. Buna göre olay pencereleri, olay çalışması kapsamında kısa ve uzun pencereler olarak belirlenmiştir. Bulgular, -50 +50 olay penceresinde tüm ülkelerdeki havayolu hisse senetleri için istatistiksel olarak anlamlı kümülatif ortalama anormal getirilerin gerçekleştiğini göstermektedir. Ayrıca, bu çalışmada olay tarihi olarak kabul edilen 11 Mart salgın duyurusunun etrafındaki kısa olay pencerelerinde, bazı ülkelerdeki havayolu pay senetleri pandemiye önemli ölçüde tepki verirken bazıları vermemektedir.Alternate abstract:The COVID-19 pandemic has struck all life, global economy, and financial markets. It stopped airline transportation in Europe and many regions of the world for a certain period as well as affecting many businesses negatively. In this process, naturally, excessive losses occurred in stock markets. Airline stocks were among the most affected by this situation. From this point of view, this study analyzes 38 airline stocks traded in the stock markets of 14 European countries with "the event study methodology". The main purpose is to compare the reaction of the airline stocks traded in the stock markets of these countries to the pandemic and to determine whether a statistically significant cumulative average abnormal return is provided from them. Accordingly, event windows are determined as short and long windows within the scope of the event study. The findings show that a statistically significant cumulative average abnormal returns for airline stocks in all countries occurred in the -50 +50 event window. Besides, in short event windows around the pandemic announcement on March 11, which is accepted as the event date in this study, airline stocks in some countries respond to the pandemic significantly, while others do not.