## 1 Introduction  
Based on the consensus of the two medical societies of the field--the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) and North American Society for PediatricGastroenterology, Hepatology and Nutrition (NASPGHAN)--an updated guide for gastroesophageal reflux disease (GERD) in children has been produced with the aim of guiding and supporting general practitioners, pediatricians in general, and pediatric gastroenterologists in particular. According to such guidelines, GER is considered to be pathologic and referred to as GERD when the reflux leads to troublesome symptoms or complications, such as esophagitis or strictures [1; 2]. To date, no biochemical marker can suggest the polymorphism of the disease, which leads to the idea that a set of biomarkers is needed in order to assess different profiles for various complications.  
About 15-40% of the world's population displays gastroesophageal reflux at least once a month, and only a quarter of these people have contacted their doctors regarding these symptoms. Moreover, it is estimated that around 7% of the world's population suffers from daily reflux [3].  
Although this disease is not regarded as life threatening, GERD is characterized by both morbidity and considerable complications, such as esophageal ulcerations, peptic stenosis or the development of Barrett's esophagus and esophageal adenocarcinoma. There is a clear level of difficulty in the assessment of GERD epidemiology in children resulting from the non-specific clinical symptoms and the lack of a \"golden standard\" for diagnosis [4; 5]. Current alternative diagnosis approaches include pH monitoring and gastroesophageal scintigraphy, which are considered to be second-line procedures. Upper digestive endoscopy is used in cases with significant digestive symptoms that do not respond to treatment in order to visualize esophagitis lesions and is also used in cases with severe symptoms [6]. When biochemical markers are quantified, complementary clinical patterns can be identified. Consequently, various biomarkers are used in clinical laboratories to detect, diagnose and monitor a wide series of comorbidity-associated pathologies [7]. Biochemical markers play an important role in the assessment of gastrointestinal conditions, including both functional ones and severe organic diseases requiring hospitalization, increased attention and significant resources [8]. The investigation protocol for GERD may include biochemical tests, besides specific diagnostic interventional procedures. Such determinations by means of laboratory tests are essential in the identification and assessment of the disease and have also proven useful for the monitoring of therapy throughout its duration [9].  
GERD can be associated with hematological modifications, and consequently, one of our objectives was the study of the complete blood count, as well as the inflammatory syndrome. The lesions within GERD can lead to hematological alterations due to occult blood loss, as well as inflammatory changes, affecting platelets and leukocytes, and may also generate deficiency alterations.  
Thus, the aim of our study was to assess a series of biochemical parameters that are associated with GERD and, secondly, to anticipate the progression of the disease, as well as to avoid the overuse of invasive diagnosis methods that are often difficult to perform. The non-compliance of parents regarding the evaluation of their children by such tests is also a recurring issue.