The study was conducted between February 2004 and June 2005 at the ED of Stockholm South General Hospital, a public general hospital with a catchment area of about 600,000 inhabitants.
Nine surgeons with at least 2 years experience of surgery after completing internship participated in the study. The surgeons attended a 1-week course given by a specialist in ultrasound examination followed by 3 weeks of training in the radiological department in abdominal ultrasound, under the guidance of an ultrasound specialist. The surgeons were trained in detecting the following disease states: gallbladder stones, cholecystitis, wide bile ducts, hydronephrosis, abdominal aortic aneurysms, ovarial cysts, free abdominal fluid, pleura fluid collections, large abdominal masses, inflamed appendix, diverticulitis, intestinal obstruction, liver disease and large kidney stones.
All patients, 18 years or older, admitted to the emergency ward for abdominal pain were eligible to participate in the study. Exclusion criteria were pregnancy, previously diagnosed abdominal condition, acute conditions needing immediate care, inability to communicate with the investigator, drug or alcohol addiction and dementia.
Eight hundred patients were enrolled for the study. After inclusion, the patients were examined by the study surgeon. Medical history was taken, and clinical examination and routine laboratory testing were performed. The study surgeon set a first preliminary diagnosis and then opened a sealed randomization envelope randomizing the patient to US or not. If randomized to the US group, the examination was performed with one out of two handheld, 2.5–5 MHz or 4.3–6 MHz, curved array transducers (B–K medical, Denmark, Hawk 2102, transducers type 8665 and 8802) screening the entire abdomen. The two groups were subsequently managed according to clinical routine as decided by the study surgeon.
The correct diagnosis was defined as the final diagnosis set by a senior surgeon 6–8 weeks after the patient had entered the study, based on information in the patient records. The senior surgeon was not aware of the preliminary diagnosis set by the surgeon at the ED. The final diagnosis was then compared with the preliminary diagnosis, with or without US examination.
All information on the patients collected in the ED was entered by the study surgeon on a case report form. Additional data about the patients who were admitted to the hospital for in-patient care were collected from the patient records and entered on a complementary case report form, designed for the admission period.
We examined selected outcomes in different subgroups based on body mass index (BMI), age, level of C-reactive protein (CRP), signs of peritonitis, symptoms predictable for appendicitis (pain and tenderness in lower right abdomen), gallbladder disease (pain and tenderness in upper right abdomen) and first preliminary diagnosis of appendicitis, gallbladder disease or non-specific abdominal pain set at the ED before randomization. The outcomes analyzed were diagnostic accuracy, admission rate and amount of further examinations ordered at the ED [US examinations and computer tomography (CT) scans from the radiological department or any other further examinations]. In the BMI groups, we also examined level of difficulty and reliability of the US examination as assessed by the examining surgeon. For patients with signs of peritonitis, we also analyzed the timing of the decision about surgery.
Chi-square test was used to compare groups regarding diagnostic accuracy, amount of requested complimentary examinations and hospital admission. If surgery was needed, we also compared the groups regarding when the decision on whether or not to perform surgery was taken. The results were regarded as significant if P was less than 0.05, two-tailed. All analyses were performed according to intention to treat using SPSS version 16.0.
The sample size was calculated on the basis of the primary outcome of the study, diagnostic accuracy, presented in an earlier article .
The patients received oral and written information from the study surgeon, and were included after informed consent. The study was approved by the Institutional Review Board at Karolinska Institutet, Stockholm, Sweden. The study has been registered in ClinicalTrials.gov ID NCT00550511.