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

KCE Reports 113 Volume Outcome 41
4.2.3 Definition of volume
The HOSPITAL volume is the number of stays selected in the definition of the
procedure.
The SURGEON volume is the number of stays selected in the definition of the
procedure, where the Performer identifier variable (from the MFD) is available in the
database. When the same surgeon operates in different hospitals, the surgeon volume is
computed across all hospitals (and not the volume in each particular hospital).
If international cut off for volume of centres or surgeon was identified in the literature,
these cut off were used in order to facilitate comparison of results. If not cut of volume
could be identified, then tertiles (dividing the hospitals in three group of the same size)
were used in cardiology and in orthopaedics. In oncology, cut off volume were chosen
in order to differentiate the providers (low versus versus medium versus high volume),
keeping sufficient number of observations in each group.
The analyses were not intended to determine thresholds but were primarily designed to
validate the existence of volume-outcome correlations. Consequently, this precludes
making recommendations about specific minimal provider volume thresholds to achieve
optimal results.
4.2.4 Definition of outcome
4.2.4.1 Outcome measures
These are the outcome measures which were obtained from the following databases:
1. In-hospital mortality: retrieved from MCD data.
2. Approximate 30-day mortality and 2-year mortality: retrieved from IMA
database.
3. Readmission rate: retrieved from MCD data.
For patients with an index admission in 2004, i.e. who were hospitalized in
2004 to undergo one of the investigated surgical procedures, we disposed of
the readmissions until the end of 2005. This information applied to
readmissions in both the same hospital as in other hospitals as the index
admission.
It has to be acknowledged that whether the patient is readmitted or not
depends on the decision of the physician and is therefore a less reliable
outcome to assess the quality of care.
4. Complication rate during index admission or readmission: retrieved from the
MCD.
Table 2.1 (page 16) illustrates which outcomes are analyzed for the different
procedures.
4.2.4.2 Quality problems of outcome measures
1. As explained in Chapter 2 (see page 15), the approximate 30-day mortality is
only an approximation. This means that this outcome measure covers a postoperative
window of at least 1 day and at most 60 days.
2. When we compared the (in-hospital) mortality encoded in MCD data with
the one registered in IMA data, it was noticed that some patients were
encoded as deceased in the MCD data while the IMA data said the contrary.
On the whole of the databases, which counted more than 280 000 patients,
we counted 1.9% of patients who were deceased in the MCD data 2004 but
alive in the IMA data 2004. In these cases, short term mortality was based on
the worst case (death in MCD or in IMA database) and long term mortality
was based on IMA data only. The rationale behind this decision is that IMA
data, which are provided by the Belgian sickness funds, are probably
substantially more reliable when the mortality date is concerned. If a patient
is encoded as deceased by the sickness funds this means that he no longer
benefits any reimbursement of his healthcare costs. An erroneous mortality