During routine examination of children heart murmurs are frequently encountered in primary care. It may be difficult to judge whether the murmur is innocent or due to a less serious heart disease in healthy children. Thus these children are frequently referred for further examinations. On average only ten percent of referred children are identified to have a heart defect. This low precision in discerning innocent and pathological murmurs in primary care goes against a high precision among experienced pediatricians.
Aim: To examine the precision in assessing heart sounds among medical students and doctors with varying levels of experience using sound samples reflecting the prevalence of heart murmurs in primary care.
Method and material:
From a sample of heart sounds recorded from healthy children six weeks to two years of age, two test sets with 25 sounds were constructed with different prevalence of innocent murmurs and 12 percent pathological murmurs. These sounds, with low to moderate strength, were presented to medical students and doctors to decide upon whether they were normal, innocent or pathological.
24 doctors and 35 medical students participated in the study. The positive predictive values for identifying pathological murmurs were 0.3 for both groups. The positive predictive values were lower in the test set with a high compared to a low prevalence of innocent murmurs. The doctors were somewhat better than the medical students to identify pathological murmurs, missing 22 percent compared to 38 percent. Fleiss kappa was 0.32 for doctors and 0.18 for medical students. Average intra-observatory agreements were 68 and 69 percent respectively.
Experience did not improve the precision in assessing heart sounds significantly in this study. Auscultation as a sole method for discerning innocent and low intensity pathological murmurs seems to be unreliable. In primary care a better tool is needed to do appropriate screening. Doctors in secondary care must proceed with more precise examinations like echocardiography to make a safe diagnosis.