Economic evaluation of sevelamer for the treatment of hyperphosphatemia in chronic kidney disease patients not on dialysis in the United Kingdom

Figures & data

Figure 1. Simplified schematic of the Markov model.

Table 1. Model inputs, assumptions, and data sources for the base-case and one-way sensitivity analyses.

Parameter	Base-case input	One-way sensitivity analysis	Data sources
Population	CKD-ND	–	Di Iorio et al.33
Time horizon	Lifetime	1.3 years	Assumption
		2.10 years
Perspective	UK NHS	–	NICE34
Discounting	3.5%	1.0%	NICE34
		2.5.0%
Mean age of starting cohort (years)	57.9	–	Di Iorio et al.33
Overall survival
Within clinical trial	Figure 2	–	Di Iorio et al.33
Beyond clinical trial	Figure 2	–	Weibull regression
Initiation of dialysis
Within clinical trial	Figure 2	–	Di Iorio et al.33
Beyond clinical trial	Figure 2	–	Weibull regression
Dose of sevelamer (g/day)	2.184	14.4*	Di Iorio et al.33
Cost of sevelamer (/g)	£0.8192	–	BNF 6236
Dose of calcium carbonate (g/day)	2.950	6.0^†	Di Iorio et al.33; National Kidney Foundation (NKF) KDOQI Guidelines19
Cost of calcium carbonate (/g)	£0.0900	–	BNF 6236
Cost of dialysis	£24,204.19	£31,479.26^§	NHS reference costs 2009–201035; UK Renal Registry 200941; Renal Association Guidelines on Haemodialysis42; Baboolal et al.46
Cost of dialysis	£24,204.20	Excluded	Assumption
AND	AND	Excluded
Initiation of dialysis	Risk of dialysis (Figure 2)
Utility for patients with CKD-ND	0.850	0.70^‡	Gorodetskaya et al.39
Utility associated with dialysis	0.720		Revicki47

Costs are in 2011 GBP.

BNF, British National Formulary; CKD, Chronic Kidney Disease; CKD-ND, Chronic Kidney Disease Not on Dialysis; NHS, National Health Service; NICE, National Institute for Clinical Excellence.

*Dose was based on the allowable maximum dose for patients.

^†Dose was based on the National Kidney Foundation (NKF) KDOQI Guidelines (1–2 g, 3 × daily)19.

^‡Based on the study by Revicki47

^§The annual cost of dialysis was calculated by combining estimates of the percentage of patients in the UK receiving hemodialysis (HD) and peritoneal dialysis (PD) from the UK Renal Registry 200941 with estimates of the frequency of HD and PD from the Renal Association Guidelines on Hemodialysis42 and per session costs for HD and PD from Baboolal et al.46. Results were multiplied by 52 to arrive at an annual cost.

Figure 2. Overall survival and time to inception of dialysis in patients with CKD-ND from the INDEPENDENT-CKD study and extrapolated to lifetime using Weibull regression analysis.

Table 2. Cost of dialysis.

	Daily cost (per patient)	Frequency of dialysis (days/year)	Total cost of dialysis (per patient)	Total annual weighted cost* (per patient)
Hemodialysis	£160.59	156	£25,052.04	£21,294.23
Peritoneal dialysis	£53.15	365	£19,399.75	£2,909.96
Average weighted total cost				£24,204.20

Costs are in 2011 GBP.

*Assumes a weighting of 85% for hemodialysis and 15% for peritoneal dialysis.

Table 3. Summary of parameter estimates and distributions for the probabilistic sensitivity analysis.

Parameter	Base-case assumption	Probabilistic sensitivity assumptions		Data source
		Parameters	Distribution
Mortality	HR = 0.45	µ = −0.79, SE = 0.350858	Lognormal	Di Iorio et al.33
Time to dialysis	HR = 0.55	µ = −0.5978, SE = 0.235201	Lognormal	Di Iorio et al.33
Daily dose of sevelamer (g)	2.184	µ = 2.184, SE = 0.0575	Normal	Di Iorio et al.33
Daily dose of calcium carbonate (g)	2.95	µ = 2.95, SE = 0.068935	Normal	Di Iorio et al.33
Cost of hemodialysis (per session)	£160.59	µ = 160.59, SE = 4.7	Normal*	NHS reference costs 2009–201035
Cost of peritoneal dialysis (per session)	£53.15	µ = 53.15, SE = 4.42	Normal*	NHS reference costs 2009–201035
Utility for patients with CKD-ND	0.85	α = 130.26, β = 22.988, SE = 0.03088	Beta	Gorodetskaya et al.39
Utility for patients receiving dialysis	0.72	α = 15.39, β = 39.57, SE = 0.06002	Beta	Gorodetskaya et al.39

Costs are in 2011 GBP.

*Because the standard error for the cost of hemodialysis and peritoneal dialysis were small relative to the mean, the gamma distribution, more commonly used to characterize a distribution of costs, was not feasible. Therefore, a normal distribution was used as the distribution type for these parameters.

CKD, Chronic Kidney Disease; CKD-ND, Chronic Kidney Disease Not on Dialysis; HR, hazard ratio; NHS, National Health Service; SE, Standard Error.

Table 4. Base-case model results for CKD patients over a lifetime (sevelamer vs calcium carbonate).

	Total cost per patient	Incremental cost per patient	Incremental LYG per patient	Incremental QALYs gained per patient	ICERs
					per LYG	per QALY gained
Calcium carbonate	£46,117	£37,282	2.0493	1.5613	£18,193	£23,878
Sevelamer	£83,399

Costs are in GBP (2011).

Discounting: 3.5%.

ICER, Incremental Cost-Effectiveness Ratios; LYG, Life-Years Gained; QALY, Quality-Adjusted Life Year.

Figure 3. Tornado diagram showing the results of the one-way sensitivity analyses.

Figure 4. Scatterplot of incremental costs and incremental QALYs based on 10,000 simulations.

Figure 5. Cost-effectiveness acceptability curve for sevelamer vs calcium carbonate.

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