Pre-test Probability of Coronary Artery Disease (CAD)

The optimal diagnostic imaging strategy depends on the pre-test probability. “For example, patients with a very high probability of CAD may be started on medical therapy, whereas in patients with an intermediate probability additional diagnostic imaging should be performed. In patients with a (very) low probability of CAD, one may consider forgoing additional testing.” CAD Consortium.

Stress testing is best limited to patients with an intermediate pretest probability of CAD to avoid false negatives in patients with high pretest probability and to avoid false positives in pts with low pretest probability (NEJM 1979;301: 230)

KTA: You do a stress test on patients with an intermediate pretest probability of CAD. Patients with a high pre-test probability should be put medical therapy ± sent to catheterization. If the stress test were negative in a patient with a high pre-test probability, you still won’t be reassured that they don’t have CAD because the stress test is not 100% sensitive. So you can skip the stress test in patients with high pretest probability. Patients with low pretest probability may not need a stress test at all.

However, in practice, most PCPs stress test patients with low pre-test probability without referral to cardiology and refer patients with intermediate and high pre-test probability to cardiology. The intermediate pre-test probability patients would definitely get a stress test from cardiology. The high-pretest patients would likely get a cath.

Exercise Stress Testing: Indications and Common Questions.

Pre-test Probability Calculators

Pre-test probability of CAD (CAD consortium), Calculator. This is more accurate. See AAFP 2017.

Diamond-Forester Pretest Probability for CAD, Calculator. Gives you the pre-test probability as low, intermediate, and high.
The Diamond-Forrester score greatly overestimated the likelihood of CAD and leads to more aggressive and invasive testing.

Things that increase the pretest probability:

1. Age: [between 40 and 90 years.]
2. Sex:
3. Type of Chest pain (Typical, atypical, non-specific)
4. Diabetes (Defined as fasting glucose levels of ≥126 mg/dL (≥7 mmol/L) or treatment with either diet intervention, oral glucose-lowering agent or insulin)
5. Hypertension (Blood pressure of =140/90 mm Hg or the use of antihypertensive drugs.)
6. Dyslipidemia (Defined as a total cholesterol of ≥200 mg/dL (≥5.2 mmol/L) or treatment with lipid-lowering drugs)
7. Smoking (Current or past smoking)
8. Also EKG changes (Q-waves, or ST abnormalities)

Diamond-Forester Pretest Probability for CAD

**The Diamond-Forrester score greatly overestimated the likelihood of CAD and leads to more aggressive and invasive testing.

Diamond-Forester Pretest Probability for CAD, Calculator.

Diamond Forester Pretest Probability for CAD

Typical Angina: 3 criteria
Age 30-39: 76% likelihood (intermediate) in men and 26% in women (intermediate)
Age 40-49: 87% likelihood (high) in men and 55% in women (intermediate)
Age 50-59: 93% likelihood (high) in men and 73% in women (intermediate)
Age 60-69: 94% likelihood (high) in men and 86% in women (high)

Atypical Angina: 2 criteria
Age 30-39: 34% likelihood (intermediate) in men and 12% in women (low)
Age 40-49: 51% likelihood (intermediate) in men and 22% in women (low)
Age 50-59: 65% likelihood (intermediate) in men and 31% in women (intermediate)
Age 60-69: 72% likelihood (intermediate) in men and 51% in women (intermediate)

Non-Anginal Chest Pain: 1 criterion or none
Age 30-39: 4% likelihood (low) in men and 2% in women (low)
Age 40-49: 13% likelihood (intermediate) in men and 3% in women (low)
Age 50-59: 20% likelihood (intermediate) in men and 7% in women (low)
Age 60-69: 27% likelihood (intermediate) in men and 14% in women (intermediate)

Asymptomatic Patient: Risk is low to very low for both men and women.

Diamond-Forester in table form

Diamond and Forrester Score for Pretest Probability of Coronary Artery Disease
Age (Years)	Sex	Typical / Definite Angina	Atypical / Probably Angina	Non-Specific / Non-anginal chest pain	Asymptomatic
30-39	M	Intermediate	Intermediate	Low	Very low
	F	Intermediate	Very low	Very low	Very low
40-49	M	High	Intermediate	Intermediate	Low
	F	Intermediate	Low	Very low	Very low
50-59	M	High	Intermediate	Intermediate	Low
	F	Intermediate	Intermediate	Low	Very low
60-69	M	High	Intermediate	Intermediate	Low
	F	High	Intermediate	Intermediate	Low

Definition of probabilities: High > 90%; Intermediate 10-90%, low < 10%, very low < 5%

References

https://www.mdedge.com/familymedicine/article/62640/stress-tests-how-make-calculated-choice Last Accessed 06/2019