Applying quantitative methods in the assessment of outcomes of pharmacotherapy of psoriasis
Healthcare providers and policy makers are faced with an ever-increasing number
of medical publications. Searching for relevant infonnation and keeping up to date
with new research findings remains a constant challenge. It has been widely
acknowledged that narrative reviews of the literature are susceptible to several
types of bias and a systematic approach may protect against these biases. The aim
of this thesis was to apply quantitative methods in the assessment of outcomes of
topical therapies for psoriasis. In particular, to systematically examine the
comparative efficacy, tolerability and cost-effectiveness of topical calcipotriol in
the treatment of mild-to-moderate psoriasis.
Over the years, a wide range of techniques have been used to evaluate the severity
of psoriasis and the outcomes from treatment. This lack of standardisation
complicates the direct comparison of results and ultimately the pooling of
outcomes from different clinical trials. There is a clear requirement for more
comprehensive tools for measuring drug efficacy and disease severity in psoriasis.
Ideally, the outcome measures need to be simple, relevant, practical, and widely
applicable, and the instruments should be reliable, valid and responsive.
The results of the meta-analysis reported herein show that calcipotriol is an
effective antipsoriatic agent. In the short-tenn, the pooled data found calcipotriol
to be more effective than calcitriol, tacalcitol, coal tar and short-contact dithranol.
Only potent corticosteroids appeared to have comparable efficacy, with less shorttenn
side-effects. Potent corticosteroids also added to the antipsoriatic effect of
calcipotriol, and appeared to suppress the occurrence of calcipotriol-induced
irritation. There was insufficient evidence to support any large effects in favour of
improvements in efficacy when calcipotriol is used in combination with systemic
therapies in patients with severe psoriasis. However, there was a total absence of
long-tenn morbidity data on the effectiveness of any of the interventions studied.
Decision analysis showed that, from the perspective ofthe NHS as payer, the
relatively small differences in efficacy between calcipotriol and short-contact
dithranol lead to large differences in the direct cost of treating patients with mildto-
moderate plaque psoriasis. Further research is needed to examine the clinical
and economic issues affecting patients under treatment for psoriasis in the UK. In
particular, the maintenance value and costlbenefit ratio for the various treatment
strategies, and the assessment of patient's preferences has not yet been adequately
addressed for this chronic recurring disease.