Answers to abstract 1
a) What is the implication of allocation being 'centralised'?
b) What are the absolute risks of VTE in the enoxaparin and placebo groups?
The absolute risk (AR) of a VTE in the enoxaparin group is 2.5% and in the placebo group is 4%.
c) What are the absolute risk reduction and relative risk reduction? What do these numbers tell us?
ARR = 4% – 2.5% = 1.5%
e) What other information, not included in the abstract, would you need to know to be able to appraise this paper?
Amongst other things, you need to look at the baseline characteristics of the groups, the exclusion and inclusion criteria, how many people they needed in each group (i.e. was the trial adequately powered), what were included in the outcomes of ‘VTE’ and ‘major bleeding events’, how the outcomes were measured, whether the difference between the results was statistically significant (i.e. what was the p-value) and side effect profiles.
ARR = 4% – 2.5% = 1.5%
RRR = (4% - 2.5%) / 4% = 37.5%
ARR: extended-duration enoxaparin reduced the absolute risk of VTE by 1.5% compared to placebo. This means that 1.5 patients per 100 treated with enoxaparin will avoid a VTE compared to placebo.
RRR: extended-duration enoxaparin reduced the relative risk of VTE by 37.5% compared to placebo. This means that for the patients treated with enoxaparin, their risk of having a VTE is reduced by 37.5% compared to placebo.
d) What are your initial conclusions about the results of this trial?
Based on just the abstract, which is not best practice, we could say that extended-duration prophylaxis with enoxaparin was more effective than placebo at reducing the risk of venous thromboembolism (VTE) in this group of patients. Major bleeding events look to be more common with enoxaparin than placebo.
e) What other information, not included in the abstract, would you need to know to be able to appraise this paper?