Cost-utility analysis
The decision tree shows the expected cost for the 6-week period as
£120.07 for the co-amoxiclav arm and £193.96 for the placebo arm.
Moreover, the expected utility of those in the co-amoxiclav arm was
0.986, compared to 0.969 in the placebo cohort.
\begin{equation}
ICER=\ \frac{\text{COST}\left(\text{Antibiotic}\right)-COST(Placebo)}{\text{QoL\ }\left(\text{Antibiotic}\right)-QoL(Placebo)}=\ \frac{\pounds 120.07-\pounds 193.96}{0.986-0.969}=-\pounds 4403.14\ \text{per\ QoL}\nonumber \\
\end{equation}The ICER calculated was -£4404.14 per QOL. An assumption can be made
that patients’ QOL will remain stable over the course of 1 year, this
gives an ICER of -£4404.14/QALY. As shown in Figure 2, the results of
the analysis indicate that the activity (co-amoxiclav prophylaxis)
dominates the current practice of providing no antibiotic prophylaxis
(placebo). It provides greater benefit at a lower cost; thus, making it
a cost-effective intervention, considerably lower than the
cost-effectiveness threshold of £30,000/QALY.
Net Monetary Benefit (NMB) and Net Health Benefit (NHB):
calculation of the NMB and NHB provides a means of expressing the ICER
in terms of a monetary or health unit, catering for simpler
interpretation. Using the NICE threshold of £30,000/QALY, the NMB is
£577.34 and the NHB is 0.019 QALYs. As these values are greater than 0,
the intervention is deemed to be cost-effective, subject to sensitivity
analysis. The NHB of 0.019 QALYs indicates that co-amoxiclav results in
a gain of 0.019 QALYs, where each QALY is valued at £30,000.