Investigations

Remember

• Ultrasound scans can diagnose recurrent DVT in patients with a recent deep vein thrombosis. ^a  
  Positive if veins non-compressible or > 2mm increase in clot diameter from last measurement.

An ultrasound scan can help diagnose and exclude a recurrent DVT

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected recurrent DVT a (pre-test probability: 38%)	deep vein thrombosis (venogram)	ultrasound scan	infinity (3.5 to infinity)	100%	0.091 (0.014 to 0.59)	5%

Note:

• Around a half of patients with DVT have normal ultrasound scans after one year. ^a