Our results confirm that an increase in pain while travelling over speed bumps is associated with an increased likelihood of acute appendicitis. Absence of pain over speed bumps is associated with a significantly decreased likelihood of appendicitis. Although the specificity was relatively low, as a diagnostic variable pain over speed bumps compared favourably with other features commonly used in diagnostic assessment, with a better sensitivity and negative likelihood ratio than all other features assessed.And some comparison data with other clinical signs (Table 2 in the article, click on image to see full-sized version):
Moreover, some patients who were “speed bump positive” but did not have appendicitis had other important abdominal diagnoses, such as a ruptured ovarian cyst, diverticulitis, or pelvic inflammatory disease...
Which indicates how poor a clinical exam is for diagnosing appendicitis. And why the CT scanner has made such an important difference. (BMJ link via Slate.)