Table 4

General study characteristics and the estimated added predictive value of carotid plaque on top of traditional risk factor assessment

First author	Year	Region	N	Mean age (years)	% Men	FU (years)	Definition marker	Endpoint	Event rate, (%)	C-statistic without plaque	C-statistic with plaque	NRI (CI), %^*
Cao23	2007	USA	5020	73	40	8	No, intermediate risk, or high risk plaque	CVD^‡	37.9	0.72	0.73	–
Mathiesen28	2011	Norway	6584	60	49	10	Sum of all plaque areas	Stroke^‡	6.0	0.74	0.75	–
Nambi9	2010	USA	13 145	54	43	15	Carotid plaque	CHD^‡	13.7	0.74	0.75	7.7 (2.3 to 11.4)
Prati33	2011	Italy	1348	18–99	47	12	Total plaque risk score	TIA, stroke, and vascular death^‡	8.5	0.88	0.90	–
Stork34	2006	The Netherlands	403	78	100	4	Sum of all plaque areas	CVD^†	7.7	0.67	0.72	–
Xie35	2011	China	3258	59	41	5	Sum of segments with plaque43	CHD and stroke^‡	4.2	0.74	0.75	10.5 (9.4 to 11.6)

The baseline prediction model used in each of the studies is described in supplementary table 1 (available online only).
↵* Intermediate risk was defined as an absolute predicted 10 year risk between 5% and 10% and 10% and 20%,9 or a 5 year predicted risk between 3% and 10%.35
↵† Fatal events.
↵‡ Non-fatal and fatal events.
CHD, coronary heart disease; CVD, cardiovascular disease; FU, follow-up; NRI, net reclassification improvement; TIA, transient ischaemic accident.