The Long Beach and Palo Alto Veteran Administration (LB-PA VA) Equation for Probability of Coronary Artery Disease

 

Patient population: The subjects were all male (done at a VA center).

 

Parameters:

(1) age in years

(2) chest pain symptoms

(3) diabetes mellitus

(4) hypercholesterolemia

(5) number of pack-years for smoking

(6) resting ST depression in mm

(7) exercise ST depression in mm

(8) ST slope

(9) METs as calculated from the final treadmill speed and grade

(10) exercise angina index (from the Duke Treadmill Exercise Test)

Parameter	Finding	Points
chest pain symptoms	none	4
	typical	1
	atypical	2
	nonanginal pain	3
diabetes mellitus	absent	0
	present	1
hypercholesterolemia	absent	0
	present	1
ST slope	normal ST slope (upsloping or ST depression < 0.5 mm)	0
	abnormal (horizontal or downsloping and ST depression >= 0.5 mm)	1
exercise angina index	no angina during exercise testing	0
	angina during or after treadmill testing but did not limit the exercise	1
	occurred and sufficient to stop testing	2

 

X for pretest probability =

= (0.03 * (age in years)) – (0.4 * (points for chest pain symptoms)) + (0.8 * (points for diabetes)) + (0.4 * (points for hypercholesterolemia)) + (0.01 * (number of pack years of cigarette smoking)) + (0.7 * (resting ST depression in mm)) – 2.1

 

pretest probability of coronary artery disease =

= 1 / (1 + EXP((-1) * X))

 

Y for post-test probability =

= (3.3 * (pretest probability)) + (0.5 * (exercise ST depression in mm)) + (0.6 * (points for ST slope)) - (0.16 * (METs)) - (0.5 * (points for exercise angina index)) – 1.2

 

where:

• Pretest probability is a decimal fraction from 0 to 1.

• Handling the ST segment changes could be a source of variability. I could not find directions for handling an elevated ST segment; since it is not a depression I assume a 0 is entered. In case a person put a negative value in for the depression, I used the absolute value for the implementation.

 

post-test probability of coronary artery disease =

= 1 / (1 + EXP((-1) * Y))

 

Consensus Approach

 

The authors combined these probabilities with those from the Morise and Detano equations to develop a consensus probability for coronary artery risk. From the consensus value the patient was stratified into a risk group for coronary artery disease.

 

Consensus Probability	Risk for Significant Coronary Artery Disease
<= 30%	low
> 30 to < 75%	intermediate
>= 75%	high

 

Patients with intermediate and high risk for coronary artery disease were sent for additional testing, which allowed > 90% of patients with significant disease to be identified.