Background The Alvarado score is a clinical scoring system used in the diagnosis of acute appendicitis. This study aimed to compare the reliability of the Alvarado score and clinical judgment and to refine the score to make it easier to use. Methods In this prospective, randomized study, patients presenting at the authors' outpatient department with suspected appendicitis during a 1-year period were assigned in weekly alternation to either group A or group B. The group A patients were treated on the basis of their Alvarado score, and the group B patients underwent treatment based on clinical judgment. The correctness of the methods was assessed by evaluation of the final histology. Statistical comparison of the data was performed using SPSS 20. Results The study investigated 269 patients (131 in group A and 138 in group B). The groups were homogeneous in terms of mean age, gender, body mass index, and American Society of Anesthesiologists score. The number of negative appendectomies was 12 (9.16 %) in group A versus 5 (3.6 %) in group B (p = 0.063). The clinical judgment had better specificity and sensitivity than the Alvarado score. For that reason, the specificity of the Alvarado score was refined using statistical methods, with weighting of certain clinical data and inclusion of new ones (e.g., ultrasound investigation). Consequently, the area under the curve by receiver operating characteristic analysis gradually increased, and the Alvarado score became more accurate. Conclusion The study findings showed clinical judgment to be more reliable in the diagnosis of acute appendicitis than the Alvarado score, but the score is a useful diagnostic aid, especially for young colleagues. The use of the new scoring system has become easier. It includes fewer criteria as well as an important and sensitive predictor: the ultrasound investigation.Acute appendicitis is the most common urgent surgical condition, with 9 % of the population affected [1]. Its differential diagnosis is extremely difficult, especially for the elderly, children, and fertile-age women, in whom it can mimic numerous gynecologic and urogenital conditions [2]. The lethality of the condition is about 0.7 %, which means that it causes the death of almost 100 patients in Hungary each year [3]. Furthermore, the number of negative appendectomies remains in the approximate range of 5-10 %, although the negative appendectomy rate (NAR) has decreased in recent decades due to better diagnostic techniques (i.e., ultrasound and preoperative computed tomography [CT]) [4].The diagnosis of acute appendicitis is based on the medical history, the physical examination, and the laboratory analysis, but imaging techniques (ultrasound and CT scan) also may be helpful. The ultrasound scan is easy to perform and inexpensive, but its result is examiner-and patientdependent. With its help, however, the number of negative appendectomies can be decreased by 10 % [5]. The CT scan