The reference price system and socioeconomic differences in ... - KCE

KCE reports 126C The reference price system. v
ANALYSIS OF BELGIAN PRESCRIPTION DATA
(2008)
METHODS
Source and linkage of databases
A stratified random sample of 10% of all prescribing GPs and 5% of all prescribing
specialists was selected in Pharmanet 2008, a database containing all ambulatory
reimbursed drug data in Belgium. For each of the selected prescribers, all patients who
received a prescription from that physician were identified. All pharmaceutical products
delivered in 2008 to those patients were selected from Pharmanet. Only prescriptions
for adults were analyzed. Data were then linked to socioeconomic characteristics of
patients (database of Intermutualistic Agency); to prescriber characteristics
(NIHDI/RIZIV/INAMI database) and small area characteristics (average level of income,
average level of education) of the patient’s residence neighbourhood (General
Socioeconomic Survey 2001).
Aggregated statistics on the whole Pharmanet 2008 were also received from the NIHDI
to describe time trends of pharmaceuticals consumption.
Selection of pharmaceutical products and statistical analysis
The analyses aimed at answering two main questions.
Cluster containing originator drugs with reference supplement
Are characteristics of patients and physicians associated with the choice between drugs
which have the same active ingredient but for which an original (incurring a reference
supplement for the patient) and a low cost version exists (often a generic without
reference supplement)?
Socioeconomic differences in the use of low cost drugs were analysed among drug
clusters in the RPS where a choice between a low cost drug (generic or original brand
with a reduced price) and a brand drug exists. This sample corresponded to
1 526 084 prescriptions distributed over 66 active ingredients (over 7 ATC-1 groups).
The percentage of low cost use was described for all molecules, and logistic regression
models were performed for 12 specific groups of drugs.
Use of the “least costly” molecule(s) within a class of drugs
Within a group of active ingredients classified within the same
therapeutic/pharmacological/chemical cluster, which patient and physician characteristics
are associated with the choice of the least costly drug(s)? This includes, but is not
limited to, low cost drugs as defined by the NIHDI (drugs without a reference
supplement).
We selected three classes from the 2009-2010 agreement between physicians and
sickness funds: Proton Pump Inhibitors (PPIs) which reduce gastric acid production
(71 315 patients), statins that lower the level of cholesterol in the blood
(84 694 patients) and ACE inhibitors & sartans, two groups of pharmaceuticals that act
on the renin-angiotensin system and that are mainly used in hypertension, heart failure
and nephropathy (83 633 patients). In addition to these groups, dihydropyridines which
are primarily used to treat hypertension (38 329 patients) were also analyzed.
The same logistic regression models were used as in the first sample, with the use of
the “least” costly molecule” (as defined by the NIHDI for 3 of the 4 groups) as the
outcome variable. The “least costly” molecule(s) within a group are omeprazole and
lanzoprazole for the PPIs, simvastatin and pravastatin for the statins, ACE inhibitors for
the group of ACE inhibitors & sartans, amlodipine and felodipine for the group of
dihydropyridines.