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Utility of computed tomography and derivation and validation of a score to identify an emergent outcome in 2,315 patients with suspected urinary tract stone

Published online by Cambridge University Press:  04 March 2015

F. Kris Aubrey-Bassler ,
Scott D. Lee ,
Richard B. Barter ,
Shabnam Asghari ,
Richard Cullen  and
Marshall Godwin
F. Kris Aubrey-Bassler*
Affiliation:
Centre for Rural Health Studies, Faculty of Medicine, Memorial University, St. John's, NL Primary Healthcare Research Unit, Faculty of Medicine, Memorial University, St. John's, NL
Scott D. Lee
Affiliation:
Faculty of Medicine, Dalhousie University, Halifax, NS
Richard B. Barter
Affiliation:
Faculty of Medicine, Memorial University, St. John's, NL
Shabnam Asghari
Affiliation:
Faculty of Medicine, Memorial University, St. John's, NL Primary Healthcare Research Unit, Faculty of Medicine, Memorial University, St. John's, NL
Richard Cullen
Affiliation:
Centre for Rural Health Studies, Faculty of Medicine, Memorial University, St. John's, NL Primary Healthcare Research Unit, Faculty of Medicine, Memorial University, St. John's, NL
Marshall Godwin
Affiliation:
Primary Healthcare Research Unit, Faculty of Medicine, Memorial University, St. John's, NL
*
Primary Healthcare Research Unit, Memorial University of Newfoundland, Agnes Cowan Hostel, Room 427, 300 Prince Philip Drive, St. John's, NL A1B 3V6; kaubrey@mun.ca

Abstract

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Objective:

Because a majority of urinary tract stones (UTSs) pass spontaneously and clinically significant alternative pathology is rare, we hypothesize that many computed tomographic (CT) scans to diagnose them are likely unnecessary. We sought to measure the impact of renal CT scans on resource use and to justify a prospective study to derive a score that predicts an emergent diagnosis in patients with suspected UTS by doing so in our retrospective series.

Methods:

We conducted a retrospective study of ED patients who had noncontrast CT of the abdomen for suspected UTS. A split-sample was used to derive and validate a score to predict the presence of an emergent diagnosis on CT.

Results:

Of the 2,315 patients (50.8% female, mean age 45 years), 49 (2.1%) had an emergent outcome observed on CT. An additional 12 (0.5%) patients had an urgent outcome and 239 (10.6%) had a urologic procedure within 8 weeks of the CT. Serum white blood cell count, highest temperature, urine red blood cell count, and the presence of abdominal pain were significant predictors of the primary outcome. A score derived using these predictors had a potential range of 22 (0.26% predicted risk, 0.5% actual risk of the outcome) to 6 (52% predicted risk). The score was moderately discriminatory with c-statistics of 0.752 (derivation) and 0.668 (validation) and accurate with Hosmer-Lemeshow statistics of 10.553 (p = 0.228, derivation) and 9.70 (p = 0.286, validation).

Conclusions:

A sensible, relevant score derived and validated on all patients presenting with symptoms suggestive of renal colic could be useful in reducing abdominal CT scan ordering.

Keywords

diagnostic errorsdecision support techniquesemergency medicinenephrolithiasisx-ray computed tomography
Type
Original Research • Recherche originale
Information
Canadian Journal of Emergency Medicine , Volume 15 , Issue 5 , September 2013 , pp. 261 - 269
Copyright
Copyright © Canadian Association of Emergency Physicians 2013

References

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