Category	US	CT	DPL
Rapid	++		+
Portable	++		+
Non-invasive	++	++
Ease of integration in resuscitation	++		+
Sensitivity			+
Specificity	+	++
Quantitative	+	++
Injury localisation	+	++
Evaluation of retroperitoneum		++
Evaluation of pericardium	++	+
Ease of interpretation	+		++
Ease of repetition	++	+
Radiation exposure	++		++
Patient acceptance	++	+
Cost	++		+
++: Significant advantage +  : Some advantage

How good is the FAST examination?

As a decision making tool for identifying the need for laparotomy in hypotensive patients (Systolic BP < 90), FAST has a sensitivity of 100%, specificity of 96% and negative predictive value of 100% (NPV). This is based on only 133 patients taken from 3 separate studies.

Need for Laparotomy in Hypotensive patients:

Study	n	sensitivity(%)	specificity(%)	npv(%)
Wherret LJ, Boulanger BR, McLellan BA et al.	69	100	96	100
Rozycki GS, Ballard RB, Feliciano DV et al.	30	100	100	100
McKenny MG, Martin L, Lentz K et al.
Total	133	100	96	100

Presence of free fluid in all blunt abdominal trauma patients:

These trials compare ultrasonography with a reference standard such as DPL, CT scan, observation or laparotomy.

Study	n	sensitivity(%)	specificity(%)	npv(%)
Ballard et al, 1999	102	28	99	85
Boulanger et al, 1996	400	81	97	96
Chiu et al, 1997	772	71	100	98
Coley et al, 2000	107	38	97	78
Hoffmann et al, 1992	291	89	97	93
Ingeman et al, 1996	97	75	96	92
Kern et al, 1997	518	73	98	98
Liu et al, 1993	55	92	95	84
McElveen et al, 1997	82	88	98	96
McKenney et al, 1996	996	88	99	98
Rozycki et al, 1993	470	79	96	95
Rozycki et al, 1995	365	90	100	98
Rozycki et al, 1998	1227	78	100	99
Shackford et al, 1999	234	69	98	92
Thomas et al, 1997	300	81	99	98
Tso et al, 1992	163	69	99	96
Wherret et al, 1996	69	85	90	93
Yeo et al, 1999	38	67	97	93
Total	6324	75	98	94

Ultrasound is less good at detecting solid organ injury with sensitivities ranging from 44 to 91% and negative predictive value of 0.72 to 0.99.

Who should perform trauma ultrasonography?

As ultrasound becomes more widespread, conflicts have developed over who should be performing the ultrasonography. Radiologists, surgeons, and emergency physicians all want to be credentialled in emergency ultrasound. The primary requisites of the sonographer are that they are competent, present during the acute phase of trauma resuscitation, and are able to repeat the FAST scan as required.

Competency in sonography requires a tutored credentialling process. The learning curve for FAST examination is fairly steep, and most are satisfactorily competent after 25 scans (20 negative, 5 positive). Some verification programmes require many more scans than this howvever, and upwards of 300 is necessary in some countries. Credentialling should include formal instruction on the principles and physics of ultrasound, skills stations, practice examinations for both negative and positive FASTs (peritoneal dialysis, ascites), and proctored instruction on the use of ultrasound in actual trauma resuscitations.