MRI of fistula in ano: inter- and intraobserver agreement and effects of directed education.
OBJECTIVE
Preoperative MRI of fistula in ano is becoming more common. This prospective study aimed to determine if a significant difference occurred in interpretation between one expert and one novice observer and to assess inter- and intraobserver agreement after both observers underwent a period of directed education. SUBJECTS AND METHODS. An outcome-derived reference standard was defined in 100 patients with suspected fistula in ano via a combination of preoperative MRI, surgical findings, and clinical outcome. The performances of a single expert and a single novice interpreter were compared with this reference standard both before and after a period of directed education, and inter- and intraobserver agreement was determined.


RESULTS
Initially the expert correctly classified significantly more fistulas than the novice (85% vs 63%, p = 0.024), but after directed education there was no significant difference, with good agreement for both the classification of the primary track (kappa = 0.71) and identification of extensions (k = 0.61). Intraobserver agreement was very good for the expert (kappa = 0.92) and novice (kappa = 0.88) for classification of the primary track and good (kappa = 0.64 and 0.74, respectively) for identification of extensions.


CONCLUSIONS
The diagnostic accuracy for fistula in ano classification using MRI was significantly higher for one expert than for one novice, though this was rectified by a short period of directed education.
Buchanan
Gordon N
GN
Department of Surgery, St. Marks Hospital, Intestinal Imaging, Middlesex, England.
Halligan
Steve
S
Taylor
Stuart
S
Williams
Andrew
A
Cohen
Richard
R
Bartram
Clive
C
D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D015588:Observer Variation; D011446:Prospective Studies; D012003:Rectal Fistula / Q000175:diagnosis* / Q000453:epidemiology