The accuracy and interobserver agreement in detecting the 'gallop sounds' by cardiac auscultation*

Study objectives: To determine the observer accuracy and interobserver agreement in identifying S-4 and S-3 by cardiac auscultation and whether they improve with increasing observer experience. Design: Prospective, blinded study. Setting: Cardiology and general internal medicine wards in a university-affiliated teaching hospital. Patients: Forty patients with a cardiac diagnosis and 6 patients without were studied. Measurements and results: Two cardiologists, one general internist, three senior and two junior postgraduate internal medicine trainees, blinded to the patients' characteristics, examined the patients and documented their findings on a questionnaire. Computerized phonocardiogram was obtained in all patients as a gold standard and was interpreted by a blinded, independent cardiologist. The mean positive predictive values for S-4 and S-3 were 51% (range, 24 to 100%) and 71% (range, 50 to 88%), respectively. The mean negative predictive values for S-4 and S-3 were 82% (range, 67 to 94%) and 64% (range, 56 to 85%), respectively. The overall interobserver agreements for detecting S-4 was K = 0.05 (95% confidence interval [CI], 0.01 to 0.09) and S-3 was K = 0.18 (95% CI, 0.13 to 0.24). There was no apparent trend in the accuracy or interobserver agreement with regard to the level of observer experience. Conclusion: The agreement between observers and the phonocardiographic gold standard in the correct identification of S-4 and S-3 was poor and the lack of agreement did not appear to be a function of the experience of the observers. The overall interobserver agreement for the detection of either S-4 or S-3 was little better than chance alone.