DÄ internationalArchive40/2014Methodological Shortcomings
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This investigation is not a field study as the data were not collected to answer a research question.

In studies aimed at comparing the efficacy of different treatments, the intervention and control groups must be comparable (1). If in the intervention group a ventricular dysfunction and cardiologist contact are required, while this is not the case in the control group, it casts doubt on the comparability of the two groups. In this study, propensity score matching was used in an attempt to establish comparability. When using this method, all variables should be included which have an impact on the event or the allocation to a certain group, if possible, not only age, sex and NYHA stage. For this, stepwise regression is not suitable (1). Important parameters related to the severity of the disease, such as the number of hospital admissions prior to study commencement, were neither considered nor reported at all.

By excluding patients who participated in the program for less than 6 months, an immeasurable time bias is introduced (2). Patients who die during this period are not considered in the intervention group, while they are in the control group. CorBene was developed in 2005; thus it can be assumed that many patients were only registered in the program in the following years. By starting the follow-up on July 1, 2005, regardless of whether or not the patient was already enrolled in the program at that time, further adds to this bias.

The method used to identify heart failure-related physician contacts remains unclear, especially since in an outpatient environment diagnoses are billed on a case basis. Two primary care physician and cardiologist contacts annually appear far too few, considering that each person insured has an average of 18 physician contacts per year (10 of these visits to primary care physicians/internists) and these numbers can increase in the 70+ age group to more than 30 contacts annually (3).

Thus we have arrived at the conclusion that the study does not constitute an appropriate basis for political decisions due to its methodological shortcomings.

DOI: 10.3238/arztebl.2014.0680b

PD Dr. PH Falk Hoffmann

Universität Bremen, ZeS, Abteilung Gesundheitsökonomie,
Gesundheitspolitik und Versorgungsforschung, Bremen

hoffmann@zes.uni-bremen.de

Dr. rer. medic. Tania Schink

Leibniz-Institut für Präventionsforschung und Epidemiologie – BIPS GmbH,
Abteilung Klinische Epidemiologie, Bremen

Conflict of interest statement

The authors declare that no conflict of interest exists.

1.
Johnson ML, Crown W, Martin BC, Dormuth CR, Siebert U: Good research practices for comparative effectiveness research: analytic methods to improve causal
inference from nonrandomized studies of treatment effects using secondary data sources: the ISPOR Good Research Practices for Retrospective Database Analysis Task Force Report-Part III. Value Health 2009; 12: 1062–73. CrossRef MEDLINE
2.
Suissa S: Immeasurable time bias in observational studies of drug effects on mortality. Am J Epidemiol 2008, 168: 329–35. CrossRef MEDLINE
3.
Grobe TG, Döring H, Schwartz FW: Barmer GEK Arztreport. Sankt Augustin:
Asgard-Verlag 2010.
4.
Hendricks V, Schmidt S, Vogt A, et al.: Case management program for patients with chronic heart failure—effectiveness in terms of mortality, hospital admissions and costs. Dtsch Arztebl Int 2014; 111: 264–70.
VOLLTEXT
1.Johnson ML, Crown W, Martin BC, Dormuth CR, Siebert U: Good research practices for comparative effectiveness research: analytic methods to improve causal
inference from nonrandomized studies of treatment effects using secondary data sources: the ISPOR Good Research Practices for Retrospective Database Analysis Task Force Report-Part III. Value Health 2009; 12: 1062–73. CrossRef MEDLINE
2.Suissa S: Immeasurable time bias in observational studies of drug effects on mortality. Am J Epidemiol 2008, 168: 329–35. CrossRef MEDLINE
3.Grobe TG, Döring H, Schwartz FW: Barmer GEK Arztreport. Sankt Augustin:
Asgard-Verlag 2010.
4.Hendricks V, Schmidt S, Vogt A, et al.: Case management program for patients with chronic heart failure—effectiveness in terms of mortality, hospital admissions and costs. Dtsch Arztebl Int 2014; 111: 264–70.
VOLLTEXT

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