"There have also been methodological drawbacks in the studies that have examined the volume-effectiveness relationship, and several suggestions for methodological improvements have recently been pointed out [11-13]. First, risk adjustment must be considered in the analyses. "
[Show abstract][Hide abstract] ABSTRACT: A common argument in the recent health policy debate is that treatment is more effective among care providers with large volumes. It is challenging, however, to examine the volume-effectiveness relationship empirically. Several suggestions have recently been made for methodological improvements in the examination of the volume-effectiveness relationship. The aim of this study is to develop an extended methodology for examining the volume-effectiveness relationship and demonstrate it for the case of hip fracture treatment.
Data consisting of 22,857 hip fracture patients from 52 hospitals in Finland in 1998-2001 were extracted from the administrative registers. The relationship between hospital and rehabilitation unit volumes and effectiveness was examined using a statistical model that allowed risk adjustments and hierarchical modeling of volume trends, developed for the purposes of this study. Four-month mortality and the alternative register-based measure of maintainability were used as effectiveness indicators.
No clear relationship was found between hospital volume and the effectiveness of hip fracture treatment, but a novel result showing an association between the rehabilitation unit volume and effectiveness was detected. The face validity of the maintainability indicator seemed to be acceptable.
The methodological ideas presented allow for improved examination of the volume-effectiveness relationship. There are no indications that patients with hip fractures should only be treated in high-volume hospitals, though it may be beneficial to centralize the rehabilitation of hip fracture patients to specialized units.
BMC Health Services Research 08/2010; 10(1):238. DOI:10.1186/1472-6963-10-238 · 1.71 Impact Factor
"The majority of studies have analysed and displayed volume as a categorical variable and, although it is statistically inferior to handling it as a continuous variable, it does overcome difficulties of visual interpretation of potential correlations along a volume gradient that are subsequently not proven to be statistically significant . However, it has the disadvantage of suggesting absolute cut-off values, which may not be appropriate or indeed intended. "
[Show abstract][Hide abstract] ABSTRACT: There has been much interest in the volume–outcome relationship within surgical specialities and the potential impact on service reconfiguration. Recent research has raised questions about the validity of the methodology used in existing volume–outcome studies. This review explores a methodological framework for assessing the volume–outcome relationship and discusses limitations of previous research. In particular reference is made to the existing urological literature in this field. Areas for improvement and the potential for future research are considered.
British Journal of Medical and Surgical Urology 09/2008; 1(2):50-57. DOI:10.1016/j.bjmsu.2008.06.004
"Various approaches to determine such a cutpoint have been used, for example, external standards, the median volume, or choice of an ''optimal'' cutpoint, which minimizes the P-value relating volume to outcome  . The disadvantages of categorizing a continuous covariate , especially by choosing a data-dependent ''optimal'' cutpoint, have been discussed and such a proceeding has been cautioned against   . "
[Show abstract][Hide abstract] ABSTRACT: The aim was to review different approaches for the derivation of threshold values and to discuss their strengths and limitations in the context of minimum provider volumes.
The following methods for the calculation of threshold values are compared and discussed: The value of acceptable risk limit, the value of acceptable risk gradient, the benchmark value proposed by Budtz-Jørgensen and Ulm's breakpoint model. The latter is extended to account for two different breakpoints. The methods are applied to German quality assurance data concerning total knee replacement.
The discussed methods for calculating threshold values differ in the kind of information that has to be specified beforehand. For the value of acceptable risk limit approach an absolute number, the acceptable risk, has to be predetermined. The value of acceptable risk gradient approach and the method of Budtz-Jørgensen require the specification of a relative change expressed in gradient and in odds, respectively. On the other hand, the threshold value according to the method of Ulm is defined as a parameter of a statistical model and no a priori specification is required.
Each of the proposed methods has benefits and drawbacks. The choice of the most appropriate approach depends on the specific problem and the available data.
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