Methodology Score: 3/5
Usefulness Score: 3.5/5
Herbst MK, Rosenberg G, Daniels B, Gross CP, Singh D, Molinaro AM, Luty S, Moore CL.
Ann Emerg Med. 2014 Sep;64(3):269-76.
This prospective study of ED patients undergoing CT scan for renal colic found that bedside ultrasound performed by the emergency provider had excellent test characteristics for diagnosing hydronephrosis if the provider had fellowship training in ultrasound, but was only moderately helpful if the provider did not have an ultrasound fellowship. While JC attendees had concerns about the possibility of selection bias due to the number of excluded patients, this paper showed that with proper training, bedside ultrasound can be useful for the diagnosis of renal colic.
By: Dr. Brandon Ritcey
(Presented February 2015)
Prospective cohort studies are, by their nature, subject to selection bias. One way to mitigate this bias is to endeavour to enrol consecutive patients as they present to the health care setting. If an investigator chooses to do this, it is important that they fully describe in their flow chart, the number of eligible patients, and the number of excluded patients stratified by reason for exclusion. If a high proportion of eligible patients are enrolled and the number and reasons for exclusions are reasonable, then the risk of selection bias can be considered mitigated by consecutive enrolment.
By: Dr. Lisa Calder