Table 3.

Negative predictive value and number needed to test for one additional discharge, according to pretest probability group and electrocardiogram/troponin results

	Sample	CAD Prevalence	Negative Predictive Value	Number Needed to Test
Pretest Probability < 50%	92	27%	95%	2.1
Pretest Probability ≥ 50%	54	65%	63%	6.6
Normal EKG and troponin	42	21%	100%	2.0
Positive EKG or troponin	104	49%	83%	2.4

Number needed to test: to avoid one further complex test. EKG: electrocardiogram; CAD: coronary artery disease.