Comparison of sensitivity and specificity of cardiac size estimation through plain chest x-ray and two echocardiography

BACKGROUND: Despite more accurate methods of cardiac imaging, plain chest X-ray (CXR) still is the first imaging method in people with suspected heart diseases. The most important application of CXR in cardiac patients is the estimation of cardiac size. There are two main methods for cardiac estimation in CXR; transverse diameter (TD) and calculation of cardiac width ratio to thoracic cage or cardiothoracic ratio (CTR). Echocardiography is a standard and more accurate method for cardiac size measurement; however, it requires more time and is costly, and is not as accessible as CXR. METHODS: This study aimed to determine the sensitivity and specificity of CXR to diagnose enlarged heart (cardiomegaly) in comparison with echocardiography. In this study, 327 adults that referred for echocardiography to Hajar Hospital (Shahrekord, Iran) during summer 2001 were recruited. Their CXR findings were compared to echocardiography. RESULTS: Mean age of the patients was 53.6 years and 46% were male. Considering the CTR ? 50% of thoracic cage width and TD ? 16 cm as normal, CTR resulted in 28.2% falsepositive and 9.2% false-negative classification for cardiomegaly. The corresponding figures for TD were 8.8%and 58.5%, respectively. CONCLUSION: In order to determine cardiomegaly, CTR had a higher sensitivity in comparison with TD; however, the specificity of TD was higher than CXR.