A method is provided for diagnosing appendicitis in a patient that includes identifying at least one symptom of appendicitis in the patient and identifying the presence of at least one molecule differentially associated with appendicitis in a fluid or tissue sample of said patient. MRP-8/14 and haptoglobin are examples of molecules differentially associated with appendicitis. Devices and kits for performing the appendicitis assays of this invention are also provided. In one embodiment, the device is in a flow-through immunoassay format for testing blood samples. Further, methods for screening for molecules differentially associated with appendicitis are provided that include the use of samples from patients being operated on for suspected appendicitis.