The effect of prior colonic imaging on endoscopic productivity: potential impact of computed tomographic colonography

If computed tomographic colonography (CTC) is used for primary colorectal cancer (CRC) screening with a small polyp size threshold to define a CTC study as positive, a substantial portion of all colonoscopies performed annually will be to follow up positive CTC examinations. Moreover, the majority of positive CTC examinations would be false positives (FP). This case-control study was undertaken to test the hypothesis that colonoscopy examinations resulting from FP CTC studies would take longer to complete than negative screening colonoscopies.

Endoscopic records of a large, urban hospital were reviewed to identify all patients who had either a positive barium enema (BE) study or flexible sigmoidoscopy (FS) and a negative follow-up colonoscopy examination (these patients were used as surrogates for CTC FP cases). For each of the 28 FP patients or cases identified, 2 screening colonoscopies performed by the same endoscopist within the same time period were identified and used as matched controls. A two-way analysis of variance test was performed to assess for differences in time to complete colonoscopies between these 2 groups, controlling for the individual endoscopist.

FP colonoscopies took an average of 24.0 minutes to complete, whereas negative screening colonoscopies took 14.9 minutes; FP colonoscopies required 61% more active time to complete. This highly statistically significant difference (P < .0001) persisted with subset analyses that only included BE or FS cases and when fellow or surgeon cases were excluded.

FP colonoscopies take longer to perform than negative screening colonoscopies. If CTC is implemented as the primary modality for CRC screening, these FP examinations could comprise a substantial percentage of the colonoscopies performed, potentially leading to a significant decrease in endoscopic productivity.