Bubo measurement project

Conducting clinical research on treatments for bubonic plague has been complicated by the lack of existing methodological frameworks to assess patient outcomes.

In the few trials that have taken place to date, bubo size has been evaluated in some as an indicator of treatment response or followed-up as an important measure of disease evolution. There is however no validated method for measuring bubo size. Anecdotally bubo size is monitored in a clinical setting in Madagascar by using a common terminology to describe size (e.g., using a comparison to the size of “petit pois” or “litchi”), research studies (such as IMASOY) have used a digital calliper to measure bubo size and in some clinical settings in the US the use of ultrasound and CT scans have been documented in a small number of case studies.

If measuring the size of the bubo is a useful clinical measure of disease evolution, an accurate low-cost and easy-to-use tool must be identified to ensure buboes can be measured in a systematic and consistent manner. We therefore conducted a study using artificial buboes made from silicone to understand the potential issues measuring buboes in a clinical setting. The study evaluates measurement accuracy and repeatability.

An important finding of the study is that those measuring the artificial buboes (the “raters”) measured the buboes less accurately and with less consistency as the size of the artificial buboes decreased. This poses a substantial risk for clinical research studies where reduction in bubo size is used as an indicator of disease evolution. As buboes are expected to decrease in size with treatment over time, our results show that there is a risk of underestimating the size of the treatment effect and not detecting changes in size of smaller buboes.

This work was supported by the UK Foreign, Commonwealth and Development Office and Wellcome.

(Reference: 216273/Z/19/Z)