Study of Tomography Of Nephrolithiasis Evaluation (STONE): methodology, approach and rationale.

BACKGROUND: Urolithiasis (kidney stones) is a common reason for Emergency Department (ED) visits, accounting for nearly 1% of all visits in the United States. Computed tomography (CT) has become the most common imaging test for these patients but there are few comparative effectiveness data to support its use in comparison to ultrasound. This paper describes the rationale and methods of STONE (Study of Tomography Of Nephrolithiasis Evaluation), a pragmatic randomized comparative effectiveness trial comparing different imaging strategies for patients with suspected urolithiasis.

METHODS: STONE is a multi-center, non-blinded pragmatic randomized comparative effectiveness trial of patients between ages 18 and 75 with suspected nephrolithiasis seen in an ED setting. Patients were randomized to one of three initial imaging examinations: point-of-care ultrasound, ultrasound performed by a radiologist or CT. Participants then received diagnosis and treatment per usual care. The primary aim is to compare the rate of severe SAEs (Serious Adverse Events) between the three arms. In addition, a broad range of secondary outcomes was assessed at baseline and regularly for six months post-baseline using phone, email and mail questionnaires.

RESULTS: Excluding 17 patients who withdrew after randomization, a total of 2759 patients were randomized and completed a baseline questionnaire (n=908, 893 and 958 in the point-of-care ultrasound, radiology ultrasound and radiology CT arms, respectively). Follow-up is complete, and full or partial outcomes were assessed on over 90% of participants.

CONCLUSIONS: The detailed methodology of STONE will provide a roadmap for comparative effectiveness studies of diagnostic imaging conducted in an ED setting.