On the other hand, when the exercise test is negative in a patient who has a very high likelihood of IHD on the basis of the history, there is a substantial chance that in reality the result is falsely negative. Thus, further testing is most useful in patients in whom the cause of chest pain is truly uncertain (ie, the probability of IHD is between 20% and 70%). It is necessary to note, however, that these probabilities relate solely to the presence of obstructive CAD and do not pertain to ischemia due to microvascular disease or other causes. They also do not reflect the likelihood that a nonobstructing plaque could become unstable and cause ischemia. A landmark study52 showed how information about the type of pain and age and sex of the patient can provide a reasonable estimate of the likelihood of IHD. For instance, a 64-year-old man with typical angina has a 94% likelihood of having significant coronary stenosis. A 32-year-old woman with nonanginal chest pain has a 1% chance of coronary stenosis.70 72 Other clinical characteristics that improved the accuracy of prediction include active or recent smoking, Q-wave or ST-T-wave changes on the ECG, hyperlipidemia (defined at the time of study as a total cholesterol level .250 mg/dL), and diabetes mellitus (defined at that time as a fasting glucose level .140 mg/dL). Of these characteristics, Table 6. 