Cost-effective analysis of clopidogrel versus aspirin for high risk patients with established peripheral arterial disease in China

Figures & data

Figure 1. Markov model structure illustrated with the sequence of events. Event-free, free of further myocardial infarction or ischemic stroke on the entry; Abbreviations. MI, myocardial infarction; IS, ischemic stroke; XX, either MI or IS.

Table 1. The transition probabilities sourced from the post-hoc analysis of the peripheral arterial disease sub-group of the CAPRIE trial.

Transitions	Hyperacute	Acute	Mid-to-late
Clopidogrel
From no event to 1st event as stroke	0.0056	0.0054	0.0087
From no event to 1st event as MI	0.0041	0.0060	0.0068
From no event to vascular death	0.0038	0.0067	0.0063
From 1st event as stroke to 2nd event as stroke	0.0820	0.0625	0.0000
From 1st event as stroke to 2nd event as MI	0.0000	0.0000	0.0000
From 1st event as stroke to vascular death	0.2295	0.0000	0.0377
From 1st event as MI to 2nd event as stroke	0.0202	0.0000	0.0000
From 1st event as MI to 2nd event as MI	0.0606	0.0400	0.0000
From 1st event as MI to vascular death	0.4242	0.0400	0.0000
From 2nd event as stroke to 3rd event as stroke	0.0000	0.0000	0.0000
From 2nd event as stroke to 3rd event as MI	0.0000	0.0000	0.0000
From 2nd event as stroke to vascular death	0.2000	0.0000	0.0000
From 2nd event as MI to 3rd event as stroke	0.0000	0.0000	0.0000
From 2nd event as MI to 3rd event as MI	0.0000	0.0000	0.0000
From 2nd event as MI to vascular death	0.0000	0.0000	0.0000
Aspirin
From no event to 1st event as stroke	0.0075	0.0101	0.0053
From no event to 1st event as MI	0.0103	0.0101	0.0085
From no event to vascular death	0.0053	0.0088	0.0083
From 1st event as stroke to 2nd event as stroke	0.0625	0.0256	0.0667
From 1st event as stroke to 2nd event as MI	0.0156	0.0000	0.0000
From 1st event as stroke to vascular death	0.1719	0.0000	0.0000
From 1st event as MI to 2nd event as stroke	0.0613	0.0000	0.0000
From 1st event as MI to 2nd event as MI	0.1104	0.0000	0.0238
From 1st event as MI to vascular death	0.3436	0.0449	0.0476
From 2nd event as stroke to 3rd event as stroke	0.3333	0.2857	0.0000
From 2nd event as stroke to 3rd event as MI	0.1111	0.0000	0.0000
From 2nd event as stroke to vascular death	0.0000	0.0000	0.0000
From 2nd event as MI to 3rd event as stroke	0.0000	0.0000	0.0000
From 2nd event as MI to 3rd event as MI	0.0000	0.0000	0.0000
From 2nd event as MI to vascular death	0.7143	0.0000	0.0000

Hyperacute, 0–6 months from previous event; Acute, 7–12 months from previous event; Mid-to-late, 13+ months from previous event.

Table 2. Relative risks of ischemic events for the PAD sub-group with high-risk factors vs the general PAD sub-group.

RR (95% CI) from no event to:	Clopidogrel	Aspirin
Risk factor: pre-existing symptomatic atherosclerotic disease
Ischemic stroke	1.63 (1.36–1.94)	1.81 (1.53–2.14)
Myocardial infarction	1.46 (1.15–1.84)	1.64 (1.33–2.01)
Vascular death	1.95 (1.55–2.46)	1.84 (1.46–2.34)
Risk factor: with multi-vascular territory involvement
Ischemic stroke	1.38 (1.15–1.66)	1.52 (1.28–1.81)
Myocardial infarction	1.41 (1.12–1.77)	1.59 (1.30–1.94)
Vascular death	1.82 (1.45–2.29)	1.81 (1.43–2.27)

Table 3. Utility values of health states in the model.

Heath states	Utility value	Distribution	95% CI	Source
First stroke	0.66	Beta	0.59–0.72	^11
Second stroke	0.44	Beta	0.40–0.48	^11
MI + stroke	0.60	Beta	0.54–0.66	^11
First MI	0.91	Beta	0.80–0.98	^11
Second MI	0.83	Beta	0.74–0.91	^11
Three events	0.31	Beta	0.28–0.34	^11

Table 4. Cost parameters used in the model.

Cost parameters	Value	Distribution	95% CI	Source
Daily price of clopidogrel (Plavix) ($)	$2.49	Lognormal	$2.34–$2.70	^16
Daily price of aspirin ($)	$0.06	Triangular	$0.01–$0.06	^16
Compliance of clopidogrel (%)	91	Beta	90–92	^9
Compliance of aspirin (%)	91	Beta	90–92	^9
Duration of clopidogrel treatment (years)	2	Constant	—	^9
Cost of no event ($)	$15.72	Gamma	$10.12–$22.37	^16^,^17
Cost of MI 0–6 months ($)	$3,664.73	Gamma	$2,371.63–$5,234.68	^16^,^17
Cost of MI subsequent months ($)	$15.72	Gamma	$10.12–$22.37	^16^,^17
Cost of IS 0–6 months ($)	$1,396.32	Gamma	$903.68–$1,994.59	^16^,^17
Cost of IS subsequent months($)	$15.72	Gamma	$10.12–$22.37	^16^,^17
Cost of vascular death ($)	$2,232.90	Lognormal	$80.39–$15,517.42	^16^,^17
Reimbursement rate for drugs (%)	70	Constant	—	^16
Reimbursement rate for other costs (%)	80	Constant	—	^16

Table 5. Cost-effectiveness analysis results.

Items	Clopidogrel	Aspirin
Risk factor: pre-existing symptomatic atherosclerotic disease
Lifetime cost	¥18,777 ($2,838)	¥12,302 ($1,859)
Medication cost	¥7,722 ($1,167)	¥808 ($122)
Event cost	¥11,054 ($1,670)	¥11,493 ($1,737)
Total LYs	8.887	8.692
Total QALY gained	8.776	8.576
ICER (incremental cost per LY)	¥33,261 ($5,026)	—
ICER (incremental cost per QALY)	¥32,382 ($4,893)	—
Risk factor: with multi-vascular territory involvement
Lifetime cost	¥18,518 ($2,798)	¥12,041 ($1,820)
Medication cost	¥7,728 ($1,168)	¥813 ($123)
Event cost	¥10,789 ($1,630)	¥11,229 ($1,697)
Total LYs	8.936	8.736
Total QALY gained	8.836	8.632
ICER (incremental cost per LY)	¥32,502 ($4,912)	—
ICER (incremental cost per QALY)	¥31,743 ($4,797)	—

Abbreviations. LY, life year; QALY, quality-adjusted life year.

Figure 2. One-way sensitivity analysis tornado diagram for PAD with the pre-existing symptomatic atherosclerotic disease sub-population. Abbreviations. RR, relative risk; CV, cardiovascular; PRE-AS, pre-existing symptomatic atherosclerotic disease; MI, myocardial infarction.

Figure 3. One-way sensitivity analysis tornado diagram for PAD with a multi-vascular territory involvement sub-population. Abbreviations. RR, relative risk; CV, cardiovascular; PVD, polyvascular disease; MI, myocardial infarction.

Figure 4. Probabilistic sensitivity cost-effectiveness acceptability curve for PAD with a pre-existing symptomatic atherosclerotic disease sub-population.

Figure 5. Probabilistic sensitivity cost-effectiveness acceptability curve for PAD with a multi-vascular territory involvement sub-population.

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