As Dr. Shoaib and his colleagues correctly point out, our economic analysis
suggested that extended antithrombotic prophylaxis with low-molecular-weight
heparin could meet a threshold of $50,000 per quality-adjusted life year
gained with home care rates of <10%. At the figure quoted by Shoaib et al.
(6.5%), our model estimates the cost-effectiveness of low-molecular-weight
heparin would be roughly $35,000 per quality-adjusted life year gained
relative to no further prophylaxis. However, while we accept that
low-molecular-weight heparin has the potential to be cost-effective at such
rates, we still believe that this is an optimistic result. First, in their own
words, the cohort Shoaib et al. refer to was prescreened to exclude patients
in whom, among other factors, "self-administration is not
possible." Our analysis considered low-molecular-weight heparin used as
routine antithrombotic prophylaxis in all patients following total hip
arthroplasty. Second, as warfarin appears to be an effective alternative, it
is important to consider the incremental cost-effectiveness of
low-molecular-weight heparin relative to warfarin. On the basis of home care
rates of 6.5% for both low-molecular-weight heparin administration and
warfarin monitoring, the incremental cost-effectiveness of
low-molecular-weight heparin relative to warfarin would be approximately
$107,000 per quality-adjusted life year gained.
The discrepancy between our baseline estimates of home care rates and those
of Shoaib et al. highlights the uncertainty around the ability to
self-administer in such a cohort. Further research is required to clarify this
important parameter.