PTP (Wells Score)	CTPAs	+ve for PE	-ve for PE	Positive predictive value
Total	289	69 (24%)	220 (76%)	23.8%
Low Risk	188	35	153	18.6%
Moderate Risk	64	23	41	35.9%
High Risk	37	12	25	32.4%
< 4 PE Unlikely	238	40	198	16.8%
> 4 PE Likely	51	29	22	56.8%