Pretest probability of DVT by Wells’ clinical prediction rules8 (%)
			High risk: 75% (CI, 63% to 81%)		Intermediate risk: 17% (CI, 12% to 23%)		Low risk: 3% (CI, 1.7% to 5.9%)
Test	Sensitivity (%)	Specificity (%)	PPV	NPV	PPV	NPV	PPV	NPV
Impedence plethysmography11	77 to 98	83 to 97	93 to 99	55 to 94	48 to 87	95 to 100	12 to 50	99 to 100
Duplex ultrasonography11	88 to 97	80 to 96	93 to 99	69 to 91	47 to 83	97 to 99	12 to 42	99 to 100
Helical computed tomography12	71	93	97	52	68	94	24	99
Magnetic resonance imaging (for calf DVT)13	56 to 100	88 to 100	93	40	49	91	13	99
d-dimer testing14	89	77	39	89	—	—	14	99