Re: Graduated compression stockings as adjuvant to pharmaco-thromboprophylaxis in elective surgical patients (GAPS study): randomised controlled trial
Dear Editor,
We read with interest the article: “Graduated compression stockings as adjuvant to pharmaco-thromboprophylaxis in elective surgical patients (GAPS study): randomised controlled trial,” and acknowledge both the clinical and economic significance of the research. However, we wish to highlight two areas that we believe warrant further clarification.
Firstly, while it is specified that “the case mix of elective surgical procedures included in this study is similar to the proportions undertaken nationally within the UK,” it would have been extremely useful to have detailed the specific operations included in this study within each specialty to allow clinicians to more accurately assess the generalisability of the results to their own patient population. The exclusion criteria and the low 90-day mortality rate in the study (0.0016%) suggest that many of these elective procedures are likely to have been very low-risk, and may not be comparable to other elective surgical populations; the average 90-day mortality of elective bowel cancer resections was around 2% between April 2013 and March 2018, for example.(1)
Secondly, we would ask the authors to further expand upon the process by which the 3.5% acceptable inferiority margin was determined. A margin of 1.5%, for instance, would result in different conclusions being drawn from the data, and we believe clarification of the reasons that the 3.5% margin was “considered to be clinically important,” is necessary. One of the main weaknesses of a non-inferiority study is the need to determine an inferiority margin; to mitigate this every attempt should be made to clearly describe a priori why this particular margin is selected based on clinical and statistical grounds.(2,3)
Without a clear explanation of the above two points we believe the conclusion of the paper that graduated compression stockings might be unnecessary in most patients undergoing elective surgery is overstated.
Rapid Response:
Re: Graduated compression stockings as adjuvant to pharmaco-thromboprophylaxis in elective surgical patients (GAPS study): randomised controlled trial
Dear Editor,
We read with interest the article: “Graduated compression stockings as adjuvant to pharmaco-thromboprophylaxis in elective surgical patients (GAPS study): randomised controlled trial,” and acknowledge both the clinical and economic significance of the research. However, we wish to highlight two areas that we believe warrant further clarification.
Firstly, while it is specified that “the case mix of elective surgical procedures included in this study is similar to the proportions undertaken nationally within the UK,” it would have been extremely useful to have detailed the specific operations included in this study within each specialty to allow clinicians to more accurately assess the generalisability of the results to their own patient population. The exclusion criteria and the low 90-day mortality rate in the study (0.0016%) suggest that many of these elective procedures are likely to have been very low-risk, and may not be comparable to other elective surgical populations; the average 90-day mortality of elective bowel cancer resections was around 2% between April 2013 and March 2018, for example.(1)
Secondly, we would ask the authors to further expand upon the process by which the 3.5% acceptable inferiority margin was determined. A margin of 1.5%, for instance, would result in different conclusions being drawn from the data, and we believe clarification of the reasons that the 3.5% margin was “considered to be clinically important,” is necessary. One of the main weaknesses of a non-inferiority study is the need to determine an inferiority margin; to mitigate this every attempt should be made to clearly describe a priori why this particular margin is selected based on clinical and statistical grounds.(2,3)
Without a clear explanation of the above two points we believe the conclusion of the paper that graduated compression stockings might be unnecessary in most patients undergoing elective surgery is overstated.
Kind regards,
Dom Proctor, Rob Bethune
References
1. The Association of Coloproctology of Great Britain and Ireland. Bowel cancer surgeon outcomes publication: explanatory notes [Internet]. 2018. Available from: https://www.acpgbi.org.uk/resources/surgeon-outcomes-explanatory-notes/
2. Food and Drug Administration (FDA). Non-Inferiority Clinical Trials to Establish Effectiveness Guidance for Industry [Internet]. 2016 [cited 2020 Jun 4]. Available from: http://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/Guidanc...
3. Committee for Medicinal Products for Human Use (CHMP). Commitee for medicinal products for human use (CHMP) guideline on the choice of the non-inferiority margin [Internet]. Vol. 25, Statistics in Medicine. London; 2006 [cited 2020 Jun 4]. Available from: https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-ch...
Competing interests: No competing interests