Cost effectiveness of case-finding strategies for primary prevention of cardiovascular disease: a modelling study

Catriona Crossan; Joanne Lord; Ronan Ryan; Leo Nherera; Tom Marshall

doi:10.3399/bjgp16X687973

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Figure 1.
Discrete-event simulation flowchart.
BMI = body mass index. BP = blood pressure. PSA = probabilistic sensitivity analysis. QALY = quality-adjusted life year. TC/HDL = total cholesterol/high-density lipoprotein. THIN = The Health Improvement Network database.
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Figure 2.
Mean cost and QALY gain per 10 000 population compared with no active case finding. CVD = cardiovascular disease. QALY = quality-adjusted life year.
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Figure 3.
Difference in net benefit per sensitivity analysis compared with base case.
RR = relative risk. SA1 = sensitivity analysis 1. SA2 = sensitivity analysis 2. SA3 = sensitivity analysis 3.

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Table 1.

Sample characteristics^{^a,^b}

Characteristic	Missing data, n (%)	Observed value	Imputed value
Age		48 (10.96)^{^c}
Male, n (%)		525 400 (49)
Ethnicity, n (%)	499 346 (46.8)
White		304 533 (28.5)
Indian		17 401 (1.63)
Pakistani		7090 (0.66)
Bangladeshi		1866 (0.17)
Other Indian		8581 (0.80)
Black Caribbean		4706 (0.44)
Black African		12 316 (1.15)
Chinese		3933 (0.37)
Other ethnic group		207 882 (19.5)
Smoking status, n (%)	45 091 (4)
Non-smoker		604 889 (57)
Ex-smoker		212 865 (20)
Current smoker		204 809 (19)
Townsend index	55 370 (5)	−0.92 (3.84)^{^c}	−0.91 (3.85)^{^c}
Body mass index	156 686 (15)	26.37 (5.19)^{^c}	26.37 (5.19)^{^c}
Systolic blood pressure	93 989 (9)	125.46 (14.69)^{^c}	125.42 (14.68)^{^c}
Diastolic blood pressure	94 080 (9)	77.01 (9.44)^{^c}	77.01 (9.43)^{^c}
Total cholesterol	581 011 (54)	5.29 (0.98)^{^c}	5.17 (0.98)^{^c}
HDL cholesterol	632 782 (59)	1.47 (0.44)^{^c}	1.45 (0.43)^{^c}
Family history CVD, n (%)		5214 (0.15%)
Family history diabetes, n (%)		9288 (0.87%)
Atrial fibrillation, n (%)		1626 (0.15%)
Rheumatoid arthritis, n (%)		7330 (0.69%)
Chronic kidney disease, n (%)		5366 (0.50%)
Taking corticosteroids, n (%)		115 186 (11%)

↵a Population aged 30–74 years, without CVD, diabetes, or prescriptions for antihypertensives or statins in THIN database (total dataset for 2013: 1 067 654).
↵b For diagnoses and other categorical variables, the absence of a clinical code is taken to mean the condition is absent.
↵c Mean (standard deviation). CVD = cardiovascular disease. THIN = The Health Improvement Network.

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Table 2.

Estimated cost and QALY gain of a case-finding strategy based on prior estimated CVD risk versus opportunistic assessment^a

Invited, %	Cut-off 10-year QRisk threshold above which patients are invited	Extra cost, £	QALY gain	Incremental cost-effectiveness ratio, £	Net benefit, £^{^b}	Probability highest net benefit, %
0	0	0	0.00	0	0	3.9
2	0.2027	18 553	6.96	2666	120 624	11.2
4	0.1667	59 689	11.26	9567	165 497	12.0
6	0.1445	109 248	14.68	14 491	184 360	10.2
8	0.1277	162 280	17.53	18 608	188 397	8.3
10	0.1142	215 722	19.89	22 645	181 994	6.7
13	0.0983	278 487	22.39	25 106	169 308	4.7
15	0.0896	298 686	23.32	21 719	167 641	4.6
20	0.0721	323 632	24.87	16 094	173 820	7.3
25	0.0590	343 949	26.08	16 791	177 566	7.6
30	0.0488	364 684	26.99	22 786	175 200	6.9
35	0.0406	386 548	27.76	28 395	168 666	6.0
40	0.0339	409 016	28.38	36 239	158 551	4.2
45	0.0283	431 764	28.86	47 392	145 452	3.2
50	0.0236	455 915	29.23	65 273	128 648	1.6
55	0.0197	480 422	29.51	87 525	107 797	1.0
60	0.0163	505 461	29.74	108 865	89 378	0.4
70	0.0110	555 955	30.04	168 313	44 747	0.2
80	0.0071	606 743	30.21	298 753	−2536	0.01
90	0.0041	656 963	30.30	558 000	−51 029	0.00
95	0.0028	681 608	30.31	2 464 500	−75 370	0.00
100	0.0006	705 732	30.32	2 412 400	−99 430	0.00

↵a Selecting 0–100% of the population for assessment compared with usual practice for 10 000 patients. Mean per 10 000 persons.
↵b Based on £20 000 per QALY gained. CVD = cardiovascular disease. QALY = quality-adjusted life year.

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Table 3.

Sensitivity analysis, individuals prioritised for invitation based on prior CVD risk estimates compared with usual care^a

Sensitivity analysis	Change	Optimum invite, %^{^b}	Risk threshold	Cost, £	Incremental QALYs	Net benefit, £^{^c}
Base case	Not applicable	8	0.1276	162 280	17.53	188 397
Uptake assessment	Reduce from 63% to 46% uptake	8	0.1276	120 310	12.99	139 516
Start medication	Reduce by 50%^{^d}	6	0.1445	69 060	7.36	78 155
Stop medication	Increase by 50%^{^e}	20	0.0721	191 759	18.47	177 579
Assessment cost	Reduce by 50% (£37.20)	40	0.0339	326 023	28.50	243 943
Annual monitoring cost	Reduce by 50% (£60.06)	30	0.0488	116 314	27.20	427 743
RR of diabetes SA1	Change from 1.31 to 0.99	30	0.0488	264 881	43.41	603 313
RR of diabetes SA2	Change from 1.31 to 1.12	30	0.0488	303 986	36.86	433 247
RR of diabetes SA3	Change from 1.31 to 1.73	2	0.2029	31 591	4.57	59 793
Utility decrement diabetes	Change from 0.131 to 0.015	30	0.0488	362 956	40.16	440 154
Disutility of treatment	Change from 0 to 0.001	6	0.1445	108 849	13.01	151 389

↵a Results per 10 000 persons.
↵b Strategy with the largest incremental net benefit is the ‘optimum’ at this threshold, yielding the greatest QALY gain while accounting for the opportunity cost of scarce healthcare resources.
↵c Based on £20 000 per QALY gained.
↵d Initiate treatment with statins, reduce from 0.683 to 0.3415, and with antihypertensives, reduce from 0.565 to 0.2825 (invitation-based strategies).
↵e Stay on statin medication, 1 year: 0.8614 to 0.4307, 5 years: 0.6877 to 0.343875; stay on antihypertensive medication, 1 year: 0.7055 to 0.35275, 5 years: 0.4905 to 0.24525. CVD = cardiovascular disease. QALY = quality-adjusted life year. RR = relative risk. SA1 = sensitivity analysis 1, SA2 = sensitivity analysis 2. SA3 = sensitivity analysis 3.

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Table 4.

Sensitivity analyses: net benefit per 10 000 persons for inviting for assessment population with 10-year CVD risk thresholds by effect on diabetes risk and varying statin treatment thresholds^a

Invited, %	Cut-off^{^b}	10-year CVD risk treatment threshold for statins (statins assumed to increase diabetes risk)
Invited, %	Cut-off^{^b}	Net benefit for 10% threshold, £	Net benefit for 15% threshold, £	Net benefit for 20% threshold, £	Net benefit for 25% threshold, £	Net benefit for 7.5% threshold, £
8	0.1276	195 319	188 397	112 700	184 396	167 790
10	0.1142	188 736	183 987	128 576	196 675	179 743
13	0.0983	159 806	172 395	144 537	208 960	193 451
15	0.0896	128 521	171 427	151 326	218 406	199 252
20	0.0721	66 060	178 734	169 385	232 759	212 812
25	0.0590	48 489	181 858	176 995	238 400	215 999
30	0.0488	42 467	181 101	180 853	237 444	215 407
35	0.0406	36 219	174 050	178 669	231 126	210 097
40	0.0339	26 217	162 976	172 179	221 274	200 799
45	0.0283	12 992	150 559	165 075	207 209	187 863
50	0.0236	−3225	132 937	156 436	191 749	172 612
8	Cut-off^{^b} 0.1276	10-year CVD risk treatment threshold for statins (statins assumed not to affect diabetes risk)
8	Cut-off^{^b} 0.1276	420 494	414 083	347 839	245 586	193 065
10	0.1142	478 593	468 227	365 636	259 219	205 668
13	0.0983	550 404	527 239	382 343	273 194	220 312
15	0.0896	585 960	547 727	392 544	283 562	226 582
20	0.0721	647 281	574 502	408 967	299 397	240 952
25	0.0590	668 209	586 376	414 148	306 451	245 221
30	0.0488	675 641	590 219	412 947	306 481	245 441
35	0.0406	675 835	586 021	406 288	300 916	241 082
40	0.0339	670 013	577 154	397 083	291 742	232 443
45	0.0283	659 702	566 787	384 913	278 268	219 889
50	0.0236	645 655	550 856	368 788	263 606	205 184

↵a Invitation based on estimated prior CVD risk versus usual care.
↵b 10-year QRisk threshold above which patients are invited. Benefit based on £20 000 per QALY gained. CVD = cardiovascular disease. QALY = quality-adjusted life year.