hta_ knee intro.qxp - Ministero della Salute

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We calculated ICERs only for classes for which cost and effect data were available for two or
more prostheses as follows:
where:
Cbs = Cost of base line prosthesis
n = comparative prosthesis
Cn = Cost of comparative prosthesis
Implant survival rate = 100 – revision rate
8.3 Results
We identified the base line prosthesis (BS) as the prosthesis with the lowest revision rate (i.e.
those for which there is the highest evidence of patient benefit). We did this using survival data
from the 2 registers (Register of the Orthopaedic Prosthetic Implants - RIPO and Australian
Orthopaedic Association National Joint Replacement Register - AOAJRR) by class of prosthesis.
The base line prosthesis was chosen on the basis of its 5 year clinical performance. As each
base line prosthesis can be considered as the best performing within its class, all other prosthesis
should be compared with these. However the highest effectiveness may not necessarily mean the
highest cost-effectiveness as the latter is the ratio of mean weighted cost to performance.
Although it is marginal (or incremental) cost-effectiveness which should be used for decision
making purposes the choice of starting the evaluation using the highest effectiveness simplifies
the calculation considerably. If a regional decision maker consults the RIPO, he or she will be able
to identify the most effective prostheses and then gather information on purchase costs and volumes
of activity in his or her region following our methodology. This simple procedure will allow
ICERs to be calculated simply and relatively quickly. However the limits of such an approach are
similar to ours. These can be summed up with the phrase “you can only use what data you have”.
Regional decision-makers may be able to identify purchase and volume data for their regions but
until their own regional registers are running and populated by data for a reasonable follow up
period they can only construct ICERs from the two sets of data (cost and effect) which may not
necessarily be for the same prostheses. For some cost and effectiveness data will be available. For
others only one or the other, and effectiveness data will necessarily be that of devices used in
Emilia-Romagna (or Australia). These considerations should be a further stimulus for all stakeholders
to coordinate the birth and development of prostheses registers and rolling regional surveys
of devices on the market and their costs.
We calculated differences in cost and effectiveness ( C and E) compared to the ICER of
the baseline prosthesis. A positive C means that the baseline prostheses is more costly than its
comparator, while a negative cost difference means the opposite. Instead E are all positive as
the baseline prostheses is always the most effective. Finally we have included the knee prosthesis
revision DRG (DRG 209 - Decree of the Ministry of Health - 12/09/2006) to compare ICERs
using a value expressing the INHS desirability of avoiding revision sustainability. If the ICER is
greater than the DRG reimbursement value the INHS is burdened with a further cost and a revision
may be preferable.