The impact of disease severity on EQ-5D and SF-6D utility discrepancies in chronic heart failure.
OBJECTIVE
To compare EQ-5D and SF-6D utilities across groups of chronic heart failure (CHF) patients with varying levels of disease severity.


METHODS
A consecutive sample (N = 251) of CHF patients undergoing elective cardiac surgery were surveyed. Disease severity was proxied via a self-assessment scale, the EQ-VAS and the Duke Activity Status Index (DASI); however, validity was demonstrated only by the latter. Association and level of agreement between instruments in DASI-based severity groups were estimated with Pearson's r and the intraclass correlation coefficient (ICC), respectively. Paired-samples t test was used to identify significant differences. In a linear regression model, the DASI was used as an anchor of disease severity to identify a potential "crossover" point between EQ-5D and SF-6D utilities.


RESULTS
EQ-5D and SF-6D strongly correlated over the entire sample (r = 0.647, P < 0.001); however, their agreement was moderate (ICC = 0.484, P < 0.001). In the less severe DASI groups (i.e. higher functional capacity) EQ-5D was significantly higher than SF-6D (P < 0.001) and differences constituted minimally important differences (MIDs). Contrarily, in the more severe groups SF-6D was predominantly higher than EQ-5D. The regression model indicated a utility crossover point at 0.722 and predicted that individuals with a utility score less than this would score higher on the SF-6D than on the EQ-5D, and vice versa. The DASI score at crossover was calculated at 31.94.


CONCLUSIONS
In subgroups of patients differing in CHF severity according to the DASI, mean EQ-5D and SF-6D indices differed significantly. Contrarily, in socio-demographic and clinical groups, these utility differences were not directly evident. According to the evidence, comparisons based on severity classification via a valid disease-specific external instrument may provide insight on instrument choice in cost-utility analyses.
Kontodimopoulos
Nick
N
Faculty of Social Sciences, Hellenic Open University, Bouboulinas 57, 26222, Patras, Greece. nkontodi@otenet.gr
Argiriou
Michalis
M
Theakos
Nikolaos
N
Niakas
Dimitris
D
D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D005260:Female; D006115:Greece; D006305:Health Status Indicators; D006333:Heart Failure / Q000191:economics / Q000503:physiopathology* / Q000523:psychology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011594:Psychometrics / Q000295:instrumentation; D011788:Quality of Life; D015203:Reproducibility of Results; D012647:Self-Assessment; D012720:Severity of Illness Index; D018434:Sickness Impact Profile; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires / Q000592:standards*
Eur J Heart Fail. 2002 Jun;4(3):361-71
12034163
Qual Life Res. 2005 Aug;14(6):1523-32
16110932
Qual Life Res. 2005 Oct;14(8):1959-65
16155784
Value Health. 2008 Dec;11(7):1162-9
18489492
Pharmacoeconomics. 2000 Feb;17(2):151-65
10947338
Cost Eff Resour Alloc. 2009 Jul 17;7:12
19615052
Health Econ. 2002 Jul;11(5):447-56
12112493
Health Econ. 2005 Nov;14(11):1169-89
15942981
Lancet. 2005 May 28-Jun 3;365(9474):1877-89
15924986
Qual Life Res. 2009 Feb;18(1):87-97
19051058
J Am Coll Cardiol. 1995 Nov 1;26(5):1115-20
7594019
Eur J Cardiothorac Surg. 1999 Jul;16(1):9-13
10456395
Qual Life Res. 2005 Jun;14(5):1433-8
16047519
Health Policy. 2008 Apr;86(1):85-96
17996975
Health Qual Life Outcomes. 2006 Mar 25;4:20
16563170
Circulation. 2008 Jan 29;117(4):e25-146
18086926
N Engl J Med. 2007 Mar 15;356(11):1140-51
17360992
Am J Cardiol. 1989 Sep 15;64(10):651-4
2782256
Health Econ. 2006 Nov;15(11):1229-36
16625671
Am J Cardiol. 2009 Jan 1;103(1):73-5
19101233
Health Econ. 2004 Sep;13(9):873-84
15362179
Eur J Cardiothorac Surg. 1999 Jun;15(6):816-22; discussion 822-3
10431864
Appl Health Econ Health Policy. 2004;3(2):91-102
15702946
Health Policy. 1996 Jul;37(1):53-72
10158943
Med Care. 2005 Jul;43(7):736-49
15970790
Am Heart J. 2002 Apr;143(4):565-76
11923792
Health Econ. 1996 Mar-Apr;5(2):141-54
8733106
Heart. 2002 Mar;87(3):235-41
11847161
Eur J Health Econ. 2005 Sep;6(3):253-60
15968563
Am J Cardiol. 1991 Oct 1;68(9):973-5
1927964
Eur Heart J. 2002 Dec;23(23):1867-76
12445536
Arch Intern Med. 1999 Aug 9-23;159(15):1690-700
10448770
J Card Fail. 1995 Dec;1(5):371-80
12836712
Value Health. 2006 Jul-Aug;9(4):262-71
16903996
J Am Coll Cardiol. 1995 Oct;26(4):914-9
7560617
Health Econ. 2008 Jul;17(7):815-32
17893863
Eur J Health Econ. 2009 Feb;10(1):15-23
18327677
N Engl J Med. 1994 Oct 27;331(17):1130-5
7935638
J Health Econ. 2002 Mar;21(2):271-92
11939242
Int J Technol Assess Health Care. 2006 Spring;22(2):235-41
16571199
J Health Econ. 1996 Apr;15(2):209-31
10159110
Health Policy. 1990 Dec;16(3):199-208
10109801
Health Econ. 2003 Dec;12(12):1061-7
14673814
Arthritis Rheum. 2007 Aug 15;57(6):1043-9
17665466
Health Qual Life Outcomes. 2003 Apr 11;1:4
12737635
Med Care. 1997 Nov;35(11):1095-108
9366889
Psychol Bull. 1992 Jul;112(1):155-9
19565683