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BMC Health Services Research
Published in: BMC Health Services Research 1/2005

Open Access 01-12-2005 | Research article

The role of 'confounding by indication' in assessing the effect of quality of care on disease outcomes in general practice: results of a case-control study

Authors: Johan S de Koning, Niek S Klazinga, Peter J Koudstaal, Ad Prins, Gerard JJM Borsboom, Johan P Mackenbach

Published in: BMC Health Services Research | Issue 1/2005

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Abstract

Background

In quality of care research, limited information is found on the relationship between quality of care and disease outcomes. This case-control study was conducted with the aim to assess the effect of guideline adherence for stroke prevention on the occurrence of stroke in general practice. We report on the problems related to a variant of confounding by indication, that may be common in quality of care studies.

Methods

Stroke patients (cases) and controls were recruited from the general practitioner's (GP) patient register, and an expert panel assessed the quality of care of cases and controls using guideline-based review criteria.

Results

A total of 86 patients was assessed. Compared to patients without shortcomings in preventive care, patients who received sub-optimal care appeared to have a lower risk of experiencing a stroke (OR 0.60; 95% CI 0.24 to 1.53). This result was partly explained by the presence of risk factors (6.1 per cases, 4.4 per control), as reflected by the finding that the OR came much closer to 1.00 after adjustment for the number of risk factors (OR 0.82; 95% CI 0.29 to 2.30). Patients with more risk factors for stroke had a lower risk of sub-optimal care (OR for the number of risk factors present 0.76; 95% CI 0.61 to 0.94). This finding represents a variant of 'confounding by indication', which could not be fully adjusted for due to incomplete information on risk factors for stroke.

Conclusions

At present, inaccurate recording of patient and risk factor information by GPs seriously limits the potential use of a case-control method to assess the effect of guideline adherence on disease outcome in general practice. We conclude that studies on the effect of quality of care on disease outcomes, like other observational studies of intended treatment effect, should be designed and performed such that confounding by indication is minimized.
Appendix
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Literature
1.
Calman KC: Report on confidential inquiries into maternal deaths in the United Kingdom 1988-1990. 1994, London, Department of Health
2.
Northern Regional Health Authority Coordinating Group: Perinatal mortality: a continuing collaborative regional survey. BMJ. 1984, 288: 1717-20.CrossRef
3.
4.
5.
Lohr KN, Sundwall DN, Bergman D: A strategy for quality assurance. Volume 1 and 2. 1990, Washington DC, National Academy
6.
Baker F, Curbow B: The case-control study in health program evaluation. Eval Progr Plan. 1991, 14: 263-272. 10.1016/0149-7189(91)90008-5.CrossRef
7.
MacMahon S, Collins R: Reliable assessment of the effects of treatment on mortality and major morbidity, II: observational studies. Lancet. 2001, 357: 455-62-10.1016/S0140-6736(00)04017-4.CrossRefPubMed
8.
Selby JV: Case-control evaluations of treatment and program efficacy. Epidemiol Rev. 1994, 16: 90-101.PubMed
9.
Joffe MM: Confounding by indication: the case of calcium channel blockers. Pharmacoepidemiol Drug Safe. 2000, 9: 113-117. 10.1002/(SICI)1099-1557(200001/02)9:1<37::AID-PDS471>3.0.CO;2-U.CrossRef
10.
Grobbee DE, Hoes AW: Confounding and indication for treatment in evaluation of drug treatment for hypertension. British Medical Journal. 1997, 315: 1151-1154.CrossRefPubMedPubMedCentral
11.
Weiss NS: Application of the case-control method in the evaluation of screening. Epidemiol Rev. 1994, 16: 102-8.PubMed
12.
Hak E, Verheij TJM, Grobbee DE, Nichol KL, Hoes AW: Confounding by indication in non-experimental evaluation of vaccine effectiveness: the example of prevention of influenza complications. Journal of Epidemiology and Community Health. 2002, 56: 951-955. 10.1136/jech.56.12.951.CrossRefPubMedPubMedCentral
13.
WHO Special Report: Stroke-1989. Recommendations on stroke prevention, diagnosis, and therapy. Report of the WHO Task Force on sroke and other cerebrovascular disorders. Stroke. 1989, 20: 1407-31.CrossRef
14.
Geijer RMM, Burgers JS, van der Laan JR, Wiersma TJ, Rosmalen CFH, Thomas S: NHG-Standaarden voor de huisarts (Dutch College of General Practitioners' guidelines). 1999, Utrecht, NHG
15.
Grol R, Thomas S, Roberts R: Development and implementation of guidelines for family practice: lessons from the Netherlands. J Fam Pract. 1995, 40: 435-9.PubMed
16.
Agency for Healthcare Research and Quality: Using clinical practice guidelines to evaluate quality of care. 1995, Rockville, MD, I and II: (AHCPR Publication no. 95-0045)
17.
de Koning JS, Klazinga NS, Koudstaal PJ, Prins A, Dippel DW, Heeringa J, Kleyweg RP, Neven AK, Van Ree JW, Rinkel GJ, Mackenbach JP: Quality of care in stroke prevention: results of an audit study among general practitioners. Prev Med. 2004, 38: 129-136. 10.1016/j.ypmed.2003.09.018.CrossRefPubMed
18.
Bergman L, van der Meulen JHP, Limburg M, Habbema JDF: Costs of medical care after first-ever stroke in The Netherlands. Stroke. 1995, 26: 1830-6.CrossRefPubMed
19.
Mant J, Murphy M, Rose P, Vessey M: The accuracy of general practitioner records of smoking and alcohol use: comparison with patient questionnaires. J Public Health Med. 2000, 22: 198-200. 10.1093/pubmed/22.2.198.CrossRefPubMed
20.
van Drenth BB, Hulscher ME, van der Wouden JC, Mokkink H, van Weel C, Grol R: Relationship between practice organization and cardiovasculair risk factor recording in general practise. Br J Gen Pract. 1998, 48: 1054-8.PubMedPubMedCentral
Metadata
Title
The role of 'confounding by indication' in assessing the effect of quality of care on disease outcomes in general practice: results of a case-control study
Authors
Johan S de Koning
Niek S Klazinga
Peter J Koudstaal
Ad Prins
Gerard JJM Borsboom
Johan P Mackenbach
Publication date
01-12-2005
Publisher
BioMed Central
Published in
BMC Health Services Research / Issue 1/2005
Electronic ISSN: 1472-6963
DOI
https://doi.org/10.1186/1472-6963-5-10

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