Het volume van chirurgische ingrepen en de impact ervan op ... - KCE

214 Volume Outcome KCE reports 113
8 DISCUSSION
Why a report on the volume outcome association in Belgium? This topic has been
studied in the US since the start of the 80s, and in other countries afterwards. Despite
suffering sometimes of some methodological shortcomings, many of these studies have
shown that, for specific procedures, patients admitted to low-volume hospitals or
treated by low-volume surgeons have worse outcomes than patients admitted to highvolume
hospitals or treated by high-volume surgeons. In Belgium, very few studies have
been performed on that subject, probably due to the difficult access to the required
data.
This study is thus a pioneer in our country, and has been designed first of all as a
feasibility study. The main research question was: Is it possible to use administrative
hospital data to examine the volume outcome relationship? To answer that question,
we selected 13 interventions from three medical domains, where literature on the
volume outcome association was abundant: oncology, cardiology and orthopaedic
surgery. This wide variety of domains and interventions allowed us to draw global
conclusions on the use of those volume indicators in the framework of improvement of
quality of care.
The answer to the above mentioned objective is cautiously positive: this study shows
that Belgian administrative hospital data can be used to study the volume outcome
relationship provided all available information is retrieved from the databases, and,
preferably, linked to clinical registries. Linkage with clinical data would be only one way
to improve the risk adjustment.
The main limitation of administrative data is the possibility to define the outcome
of interest for each procedure. Many procedures that were analyzed in the literature
could not be analyzed on our data because of the lack of information on the outcome.
Examples include incontinence and quality of life after transurethral prostatectomy,
adhesions in women who had a caesarean section, loss of mobility and residual pain
after total hip arthroplasty.
For those procedures where it is possible to define the outcome of interest, the
necessary precautions that should be taken in the analysis are listed in the 9 points
below.
1. Great care is needed in identifying the study population in the
administrative databases. Surgical procedures are coded with two different
coding systems: the ICD-9 classification in the minimal clinical data (MCD)
and the NIHDI billing codes (nomenclature) in the minimal financial data
(MFD). There is no 1:1 equivalence between these two coding systems, and,
depending on the intervention, the ICD-9, the nomenclature, or both are
needed to obtain a precise description of the procedure. The reason for
intervention (i.e. principal diagnosis in MCD) is also necessary to include or
exclude specific groups of patients.
2. Serious thoughts must be given to the time horizon, i.e. the time between
the intervention and the evaluation of the outcome. The choice of time
horizon depends on whether the intervention is complex and therefore high
risk, and whether the interest is on the surgeon volume or the centre
volume.
a. For complex and therefore high risk procedures such as oesophageal
cancer surgery or CABG, outcomes can be assessed at short term (inhospital,
3-months or 6–months mortality). For less complex procedures
or conditions with a good prognosis, such as breast cancer, outcome
cannot be assessed at short term simply because there are not enough
events. In these cases, evaluation has to be performed in a longer-term
perspective, keeping in mind that other treatments besides surgery affect
patient’s survival. Ideally, the outcome measure should be adapted for
each procedure.