Comparison of population screening tools for coronary artery disease with myocaridail perfusion imaging in adult population in Karachi
Date of Award
Master of Science in Epidemiology & Biostatistics (MSc Epidemiology & Biostats)
Community Health Sciences
Coronary artery disease (CAD) is an important public health challenge and has become one of the leading causes of mortality in both developed and developing world. It is no more a disease of affluent and estimates suggests that nearly 85% of the global mortality and disease burden from cardiovascular diseases is borne by low- and middle income countries. There is considerable interest in the diagnosis of CAD in an asymptomatic phase because advanced obstructive CAD can exist with minimal or no symptoms and can progress rapidly. The first clinical manifestation is often catastrophic: acute myocardial infarction (MI); unstable angina; or sudden cardiac death. There is evidence that detection of CAD during sub clinical stages of disease permits the identification of subjects at increased risk of an adverse cardiac event and that primary and secondary prevention strategies might improve the prognosis of those at high risk. We conducted a cross sectional study to 1) compare and validate Rose questionnaire and Minnesota coded ECG with stress myocardial perfusion imaging (MPI) as screening tools for coronary artery disease in adult population in Karachi. 2) To determine the prevalence of CAD based on MPI. 269 participants randomly selected form the 12 low income communities in Karachi completed the study. The Rose questionnaire was administered and a standard 12 lead resting ECG was performed, followed by a MPI scan at the Aga Khan University Hospital. The prevalence of CAD according to MPI was 8.6% (95%CI: 5.2-11.9%). The prevalence's according to RQ and ECG were 10.8% (95%CI: 8.9-12.7%) and 19.7% (95%CI: 14.9-24.41%). Overall RQ and ECG were found to be less sensitive in detection of coronary artery disease [Sensitivities: RQ=26% (95%CI: 11.1-48.7%); ECG=26% (95%CI: 11.1-48.7%] and positive predictive value 20.7% (95% CI: 8.7- 40.3%) for RQ and 11.3% (95% CI: 4.7-23.7%) for ECG. Specificities for both the tests were high. RQ 91% (95% CI: 86.1-94.0%) specific with NPV of 93% (95%CI: 88.7-95.7%). The corresponding values for ECG were 80.9% (95%CI: 75.3-85.5%) and 92.1% (95%CI: 80.5-97.4%). Even the combined analysis that is positive on either RQ or ECG showed only 43.5% (95% CI: 23.9 — 65.1%) sensitivity for detection of CAD compared to MPI. Positive predictive value also remained low on combined analysis 13.3% (95% CI: 6.9-23.6%) Our finding suggests that RQ and ECG are inconsistent in detecting obstructive CAD compared to stress myocardial perfusion imaging (MPI) and cannot be used as screening too]. Since MPI detects only > 50% stenosis in the coronary arteries, further studies comparing RQ and ECG with coronary angiography may be required to explore their validity for non- obstructive CAD in our population.
Abbas, S. S. (2007). Comparison of population screening tools for coronary artery disease with myocaridail perfusion imaging in adult population in Karachi (Unpublished doctoral thesis). Aga Khan University, Karachi, Pakistan.