Answers to abstract 2

Last updated: Monday, September 21, 2015

a) What are the absolute risks of infection in the chloramphenicol and placebo groups?
The AR in the chloramphenicol group is 6.6% and in the placebo group is 11.0%.

b) What are the absolute risk reduction and relative risk reduction?
ARR = 11.0 – 6.6% = 4.4%
RRR = (11.0 – 6.6) / 11= 40%

c) Calculate the NNT.
NNT = 100%/ 4.4% = 22.7, rounded up to 23.
So you would need to treat 23 patients undergoing minor surgery with chloramphenicol rather than placebo to prevent one infection.

d) What can you conclude from these results?
Chloramphenicol ointment applied after minor dermatological surgery was more effective than paraffin ointment in preventing infections. The P value was statistically significant.

e) What other information, not in the abstract, would you need to help you decide if the results of the paper could be generalised to patients having minor dermatological surgery in a UK general practice?
We would need to know if the patients included in the trial were similar to those seen for minor dermatological surgery in primary care in the UK. The abstract states that the study was undertaken in Queensland, Australia. Referral to the full paper uncovers that the trial was performed in a tropical area with high temperatures and humidity. This could be a limitation to generalising the results to the UK. We would also need to know the baseline characteristics of the patients included in the trial, such as age and co-existing medical conditions, as well as the exclusion and inclusion criteria, and surgical procedures used.