Appendiceal diameter as a predictor of appendicitis in children: improved diagnosis with three diagnostic categories derived from a logistic predictive model.
OBJECTIVE
To develop and assess the performance of a diameter-based logistic predictive model and a derived 3-category interpretive scheme for the sonographic diagnosis of paediatric appendicitis.


METHODS
Appendiceal diameters were extracted from reports of ultrasound examinations in children and young adults. Data were used to generate a logistic predictive model which was used to define negative, equivocal and positive interpretive categories. Diagnostic performance of the derived 3-category interpretive scheme was compared with simulated binary interpretive schemes.


RESULTS
Six hundred forty-one appendix ultrasound reports were reviewed with appendicitis present in 181 (28.2 %). Cut-off diameters based on the logistic predictive model were ≤6 mm = normal, >6 mm-8 mm = equivocal and >8 mm = positive with appendicitis present in 2.6 % (11/428), 64.9 % (72/111) and 96.1 % (98/102) of cases in each group. These cut-offs conferred 97.2 % accuracy with 17.3 % (111/641) of cases considered equivocal. Of the binary cut-offs, a 6 mm cut-off performed best with 91.6 % accuracy. AIC analysis favoured the logistic model over the binary model for prediction of appendicitis.


CONCLUSIONS
A 3-category interpretive scheme based on a logistic predictive model provides higher accuracy in the diagnosis of appendicitis than traditional binary diameter cut-offs. Inclusion of an equivocal interpretive category more accurately reflects the probability distribution of prediction of appendicitis by ultrasound.


CONCLUSIONS
• Three diameter categories outperform a 6-mm cut-off to diagnose appendicitis • Three categories allow more confident exclusion of appendicitis • Three categories allow more confident diagnosis of appendicitis • Three categories more accurately reflect the probability of appendicitis by ultrasound.
Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA, andrew.trout@cchmc.org.
Andrew T
AT
Trout
Alexander J
AJ
Towbin
Shelby R
SR
Fierke
Bin
B
Zhang
David B
DB
Larson
D000208:Acute Disease; D000293:Adolescent; D001062:Appendectomy / Q000379:methods; D001064:Appendicitis / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D001065:Appendix / Q000000981:diagnostic imaging / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009929:Organ Size; D014463:Ultrasonography; D055815:Young Adult