Category	Ultrasonography	CT
Accuracy	71% to 97%	93% to 98%
Sensitivity	85% to 90%	87% to 100%
Specificity	47% to 96%	95% to 99%
Negative predictive value	76%	95%
Patient types	Pregnant women and women of childbearing age, children	All types; avoid in pregnant women
Approximate cost*	$250	$750
Advantages	Easily available, noninvasive, no radiation, rapid, no preparation needed, ability to diagnose other sources of pain (especially gynecologic disorders)	More accurate, better identification of phlegmon and abscess, may complement ultrasonography when results are suboptimal, better ability to detect normal appendix
Disadvantages	Operator dependent, not as accurate as CT, difficult with large body habitus, cannot rule out appendicitis if negative appendix is not apparent	Radiation exposure, patient discomfort/risk if contrast media used, cost