Inward or Outward Costophrenic Angles: A Simple Sign on Chest X-ray for the Screening of Metabolic Syndrome

Abstract

Prevention of cardiovascular diseases is a top-priority issue in Japan. To this end, we have developed a new screening method for metabolic syndrome (MetS) using chest X-ray. We recruited 200 patients who visited our outpatient cardiology clinic from March 2014 to August 2014. Patients with severe lung disease, acute coronary syndrome, and end-stage renal failure were excluded. We collected data on each patient's medical history, laboratory results, waist circumference (WC), body weight, and height. Additionally, we measured two parameters from the chest X-ray: (A) width at the level of right dome of diaphragm and (B) width between the costophrenic (CP) angles. We classified the CP angles as either inward (A≥B) or outward (A<B). Increased WC was defined as ≥85cm in males and ≥90cm in females. Patients with outward CP angles had a significantly larger WC compared to those with inward CP angles (92.3±8.9 vs. 80.5±7.8cm, P<0.001). In particular, the percentage of male patients with increased WC (≥ 85cm) was significantly higher in patients with outward CP angles than in those with inward CP angles (89.2% vs. 41.3%, P<0.001). Body weight and BMI were both significantly higher in patients with outward CP angles than in those with inward CP angles in both gender groups. When laboratory data and risk factors were compared, patients with outward CP angles and those with positive WC criteria consistently tended toward high morbidity from hypertension, dyslipidemia, and diabetes. The inward/outward CP identified candidates for MetS, especially in the male subjects. Chest X-ray could become a useful screening tool for the detection of increased WC and coronary risk factors.