Abstract 9412: Establishing a Coronary Calcium Scoring Threshold as a Gateway to Invasive Testing for Firefighters Undergoing Fitness for Duty Exams

Abstract

Introduction: Heart disease is the leading cause of death amongst active firefighters. Firefighters undergo exercise treadmill test as a part of fitness for duty examinations screening for heart disease. It has been previously shown that coronary artery calcium (CAC) scoring and CT angiography (CTA) together can be used cost effectively in further screening for obstructive coronary artery disease amongst firefighters. A coronary artery calcium score threshold to predict obstructive CAD however is yet to be established. Methods: Firefighters in the County of Los Angeles Fire Department underwent fitness for training tests over a twenty-year period using treadmill ECG tests for cardiac screening. Those with positive tests were referred for further evaluation with coronary calcium scoring (CCS). Individuals with a CCS of > 10 went on to have CTA as prior studies have shown that CCS < 10 is highly unlikely to correlate with obstruction. We used receiver-operating characteristic (ROC) analysis to determine the optimal sensitivity and specificity of a CCS threshold needed to predict which individuals were likely to have a CTA showing greater than 50% stenosis. Results: Annually, about 3000 firefighters undergo fitness for duty testing in Los Angeles County. In our sample population from 1999 to 2019, a total of 1425 firefighters had a positive treadmill test. All 1425 of these firefighters underwent CCS with scores varying from 0 to 1400, the distribution vastly skewed toward 0. A ROC curve analysis indicated that a CCS score of 75 was the optimal cutoff for sensitivity (82%) and specificity (62%), in predicting a stenosis greater than 50% in any segment in the CTA firefighter population. However, given the high stress associated with firefighter duty and the high mortality both on-duty and after-duty, we believe prioritization should be geared toward detection and prevention. For this reason, we chose to maximize sensitivity in our statistical analysis and determined that a CAC score of 10 (sensitivity 95%, specificity 13%) to be the most appropriate threshold. Conclusion: For future testing, a CCS threshold score of 10 can confidently be used to guide further testing for obstructive coronary artery disease with CTA.