Table 6.

—[Sections 3.2-3.6] Summary of Findings of Diagnostic Studies Evaluating CT Scan Venography, MR Venography, and MR Direct Thrombus Imaging in Patients with Suspected First Lower Extremity DVT: Accuracy Studies

Technique	Population and Reference Standard	Number of Studies	Quality of Evidence	Illustrative Comparative Numbers: Effect/1,000a
				True Positives (Correctly Classified as Having DVT)	True Negatives (Correctly Classified as Not Having DVT)	False Positives (Incorrectly Classified as Having DVT)	False Negatives (Incorrectly Classified as Not Having DVT)
CT scan venographyb	Population: predominantly suspected PE	Meta-analysis of 13 plus 5 additional primary studies125-129,133	Lowc	Prevalence 5%, 48	Prevalence 5%, 904	Prevalence 5%, 46	Prevalence 5%, 2
	Reference standard: predominantly US			Prevalence 17%, 163	Prevalence 17%, 790	Prevalence 17%, 40	Prevalence 17%, 7
				Prevalence 53%, 508	Prevalence 53%, 447	Prevalence 53%, 23	Prevalence 53%, 22
MR venographyd	Population: predominantly suspected DVT	Meta-analysis of 13 plus 1 additional primary studie144,145	Lowe	Prevalence 5%, 46	Prevalence 5%, 901	Prevalence 5%, 49	Prevalence 5%, 4
	Reference standard: predominantly contrast venography			Prevalence 17%, 158	Prevalence 17%, 787	Prevalence 17%, 43	Prevalence 17%, 14
				Prevalence 53%, 486	Prevalence 53%, 446	Prevalence 53%, 24	Prevalence 53%, 45
MR direct thrombus imagingf	Population: suspected DVT	1 Primary study146	Lowg	Prevalence 5%, 47	Prevalence 5%, 874	Prevalence 5%, 76	Prevalence 5%, 3
	Reference standard: contrast venography			Prevalence 17%, 160	Prevalence 17%, 764	Prevalence 17%, 66	Prevalence 17%, 10
				Prevalence 53%, 498	Prevalence 53%, 432	Prevalence 53%, 38	Prevalence 53%, 32

GRADE Working Group grades of evidence: High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. PE = pulmonary embolism. See Table 1 and 3 legends for expansion of other abbreviation.

^aPrevalences for high (53%), moderate (17%), and low (5%) taken from Wells et al.¹⁰

^bBased on a combined specificity of 95.2% (95% CI, 93.6%-96.5%) and sensitivity of 95.9% (95% CI, 93.0%-97.8%).

^cSerious limitations (in adequate reference standard), moderate inconsistency (significant heterogeneity between studies), serious indirectness (most studies were in suspected PE, few in suspected DVT; no management studies), and moderate imprecision (reported specificities range from 93%-100%; reported sensitivities range from 59%-100%).

^dBased on a combined specificity of 94.8% (95% CI, 92.6%-96.5%) and sensitivity of 91.5% (95% CI, 87.5%-94.5%).

^eNo major limitations, moderate inconsistency (significant heterogeneity between studies), moderate indirectness (no management studies), and serious imprecision (reported specificities range from 43%-100%, reported sensitivities range from 0-100%).

^fBased on a specificity of 92% (95% CI, 80%-98%) and sensitivity of 94.9% (95% CI, 84%-97%).

^gNo significant limitations, only single study, and moderate indirectness (management studies).