Cost-analysis model of colonoscopy preparation using split-dose reduced-volume oral sulfate solution (OSS) and polyethylene glycol with electrolytes solution (PEG-ELS)

Figures & data

Figure 1. Model flow diagram for simulation cohort.

Figure 2. Model flow diagram illustrating cost difference calculation for a single colonoscopy cycle. The cost difference in colonoscopy screening for a single colonoscopy cycle is illustrated in the schematic model. The cumulative cost difference in colonoscopy screenings over the time horizon accounts for varying recommended post-colonoscopy intervals, which are determined by colonoscopy cleansing score and polyp detection for each colonoscopy cycle.

Table 1. Summary of inputs for one-way sensitivity analyses.

Parameters	Input values
	Base case	Lower bound	Upper bound
Cost
Cost of completed colonoscopy	$1731.66	$432.92 (75% decrease in cost)	$3030.41 (75% increase in cost)
Cost of OSS	$41.77	$143.10^a	$41.77
Cost of PEG-ELS	$7.15 (Generic)	$7.15 (Generic)	$10.56 (Brand)
Colonoscopy completion
Annual colonoscopy completion rate	62% (Physician-scheduled)	25%	100%
Assumptions regarding non-completers^b	All have a delayed colonoscopy	All are lost to follow-up	All have an aborted colonoscopy
Other
Average surveillance intervals by cleansing score and polyp finding	Median of the recommended surveillance interval used	Minimum of the recommended surveillance interval used	Median of the recommended surveillance interval used^c
Time horizon observed	Up to age 75	Up to age 65	Up to age 85
Proportion of high risk patients	3%	0%	100%
Bowel preparation quality (excellent and good)	95%	70%	95%

a = when the cost of OSS is $143.10, there is negligible overall cost difference between for the OSS and PEG-ELS cohorts.

b = non-completers include patients who scheduled a colonoscopy, but did not show up and patients who experienced an aborted colonoscopy.

c = when the maximum of the recommended surveillance interval is used, the overall cost difference is in between the overall cost differences calculated using the median and minimum recommended surveillance intervals.

Figure 3. Cumulative colonoscopy cost.

Figure 4. Comparison of cost components associated with OSS use. Compares the cost differences between OSS and PEG-ELS for cleansing agent cost and colonoscopy procedure cost separately. The cost differences between OSS and PEG-ELS are observed as early as 5 years. Over the time horizon, the cost model shows that the cost savings for OSS increase more rapidly than additional costs incurred in the years after colonoscopy referral.

Figure 5. Univariate sensitivity analysis, tornado diagram. Illustrates the robustness of the cost model under different assumptions about costs (procedure and cleansing agent), rate of colonoscopy completion, and other inputs (i.e., average surveillance intervals, time horizon observed, and proportion of high risk patients). Positive cost difference means that cost savings were observed for the OSS cohort and negative cost difference means that cost savings were observed for the PEG-ELS cohort.