Chest radiography and abdominal ultrasound in general practice

Abstract

Chest radiography (CXR) and abdominal ultrasound (US) are two widely used diagnostic imaging techniques in Western societies. General practitioners (GPs) in The Netherlands annually request approximately 500,000 CXRs and 200,000 abdominal US, and therefore clearly place a burden on health care. Besides, diagnostic investigations may lead to incidental findings, or to additional unnecessary diagnostic procedures. Little is known on the diagnostic yield of CXR and abdominal US in patients referred by GPs. The objective of this thesis was to determine the clinical effectiveness of CXR and upper abdominal US in general practice. Large part of this thesis was based on a prospective cohort study conducted from April 2003 to December 2004, with the participation of 78 GPs in the catchment area of three general hospitals located in The Netherlands. All patients of 18 years and older who were referred for CXR or upper abdominal US by their GP were included in the study, resulting in a study population of 1300 patients (870 CXRs and 430 upper abdominal US). All GPs were asked to fill in a standardized form before and after the radiological investigation, including information on the suspected diagnosis, and proposed patient management. Clinically relevant abnormalities were found in 24% of the CXRs. Anticipated patient management changed in 60% of the patients following CXR. The main changes included fewer referrals to a medical specialist (from 26% to 12%), a reduction in initiation or change in therapy (from 24% to 15%), and more frequent reassurance (from 25% to 46%). A change in patient management occurred more frequently in patients with complaints of cough, exhibited abnormalities during physical examination, or a suspected diagnosis of pneumonia. Pneumonia was diagnosed by GPs in 35 of 192 primary care patients suspected of pneumonia (18%), of whom 27 patients (14%) had a positive CXR, and 8 patients (4%) a negative CXR, however with an assumed high probability of pneumonia by the GP. CXR clearly influenced the diagnosis of pneumonia by the GP in 53% of the patients: CXR ruled out pneumonia in 47%, and the probability of pneumonia substantially increased in 6% of the patients. Anticipated patient management changed after CXR in 69% of the patients. Clinically relevant abnormalities were found in 29% of the abdominal US, mainly cholelithiasis. Anticipated patient management changed in 64% of the patients following abdominal US. Abdominal US substantially reduced the number of intended referrals to a medical specialist (from 45% to 30%), and more patients could be reassured by their GP (from 15% to 43%). A change in anticipated patient management occurred more frequently in patients with a prior cholecystectomy. Almost 50% of the patients were referred for abdominal US because of a clinical suspicion of gallstones. Cholelithiasis was detected with US in 29% of the patients with, and 11% without a clinical suspicion of gallstones. Marked differences were found in signs and symptoms of patients suspected of gallstones with and without cholelithiasis detected on abdominal US, and in patients with expected and unexpected gallstones.