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A MULTI-CENTRE RANDOMISED DOUBLE-BLIND PLACEBO-CONTROLLED TRIAL
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Follow-up
All patient symptoms reported to their general practitioner up to one month after the
procedure were assessed for their likelihood of being related to alfentanil by two blinded
anaesthesiologists (S.E. and M.W.H.).
Image evaluation
Two independent observers (T.N.B. and G.K., both evaluated > 250 CT-colonographies)
evaluated all CT images for distension, collapse, diagnostic adequacy, and diverticulosis.
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Evaluation was done for six segments separately and distension and collapse was also
evaluated for prone and supine separately. Bowel distension was scored on a 4-point scale
based on the worst part of the segment (0-25%, 25-50%, 50-75% and 75-100% distension).
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The presence of collapse was scored (yes or no). To assess diagnostic adequacy, observers
scored whether detection of ≥ 6 mm lesions was possible based on the distension of prone
and supine position combined (yes or no). Diverticulosis was scored on a 4-point scale.
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Statistics
All calculations were performed using SPSS version 18.0 (SPSS inc., Chicago, Illinois, USA)
and a p value of <0.05 indicated a statistically significant difference. All data entry was
completed before deblinding. For the difference in maximumpain score during insufflation,
we used a one-sided independent samples t-test. Univariate analyses were performed with
linear regression to identify possible confounders. The four most influential variables with a
p<0.1 would be included in a multivariate analysis.
For time calculations and pain scores per position we used a two-sided independent
t-test. Differences between categorical values were determined using a Chi-square test
and binary values with the Fishers exact test. A (weighted) kappa was calculated to assess
inter-observer agreement with regards to distension, collapse, diagnostic adequacy, and
diverticulosis scores. We used the first observer scores to perform ordered regression for
distension scores. Variables with p<0.1 in univariate analysis were added to the regression
analysis as confounder (diverticulosis, BMI, and spasmolytic were tested). Logistic regression
was used for collapse and diagnostic adequacy scores.