The study of disease is one of the key concepts in medical sciences. Disease, like other health issues is not exclusively scientific concept. Absolutely everyone has a memory or an intuitive comprehension of the disease and it has long been one of the major human concerns [1]. In medical science, disease or illness is defined as any impairment or disability of ordinary physiological condition or function of the human body that is characterized by broadly sign and symptoms [2, 3]. In fact, the disease is a set of observable sign and symptoms that should be interpreted by physicians. This interpretation process has to be done by diagnosis process. Disease diagnosis like many terms in a medical context cannot be indicated with the clear definition; however, in general medicine, it refers to the complicated process of decision making leading to an accurate understanding of patient’s health problem [4]. Since disease diagnosis is the fundamental in clinical decision making, it involves with different subjective and objective factors. Therefore, the accurate and timely diagnosis has the most important role in determining disease or disorder. Hence, until a definitive diagnosis is not determined, the treatment plan cannot be formulated [5]. Diagnosis is recognized as a complex and difficult process for healthcare professionals because the physicians have to simultaneously consider the various factors and circumstances with regard to medical evidence [6]. Due to the complexity of clinical diagnostic process as one of the main task of physicians, all health professionals try to reduce uncertainty in diagnosis by means of collecting empirical data to manage a patient’s problems. In fact, disease diagnosis is a clinical reasoning process in which advantageous information are provided to improve healthcare quality [5, 7]. But with all these considerations, disease diagnosis may be performed with unwanted errors for its vague nature and complexity. In other words, since each patient might show the different degree of suspicion to various diseases, disease diagnosis is always established with uncertainty. This uncertainty can be originated from the vague nature of the disease, patient’s data, and complicated medical diagnosis process. In addition, this ambiguity is related to inherent nature of medicine [8, 9].