A systematic review of the clinical profile of patients with bubonic plague and the outcome measures used in research settings

Abstract

Background: Plague is a zoonotic disease that, despite affecting humans for more than 5000 years, has historically been the subject of limited drug development activity. Drugs that are currently recommended in treatment guidelines have been approved based on animal studies alone – no pivotal clinical trials in humans have yet been completed. As a result of the sparse clinical research attention received, there are a number of methodological challenges that need to be addressed in order to facilitate the collection of clinical trial data that can meaningfully inform clinicians and policy-makers. One such challenge is the identification of clinically-relevant endpoints, which are informed by understanding the clinical characterisation of the disease – how it presents and evolves over time, and important patient outcomes, and how these can be modified by treatment. Methodology/ Principal findings: This systematic review aims to summarise the clinical profile of 1343 patients with bubonic plague described in 87 publications, identified by searching bibliographic databases for studies that meet pre-defined eligibility criteria. The majority of studies were individual case reports. A diverse group of signs and symptoms were reported at baseline and post-baseline timepoints – the most common of which was presence of a bubo, for which limited descriptive and longitudinal information was available. Death occurred in 15% of patients; although this varied from an average 10% in high-income countries to an average 17% in low- and middle-income countries. The median time to death was 1 day, ranging from 0 to 16 days. Conclusions/ Significance: This systematic review elucidates the restrictions that limited disease characterisation places on clinical trials for infectious diseases such as plague, which not only impacts the definition of trial endpoints but has the knock-on effect of challenging the interpretation of a trial’s results. For this reason and despite interventional trials for plague having taken place, questions around optimal treatment for plague persist.

Bubonic plague: Can the size of buboes be accurately and consistently measured with a digital calliper?

“…( 9) Across 91 clinical studies published in peerreviewed journals between 1902 and 2021, 18 (20%) recorded the size of the bubo on at least one occasion. (10) Of the three clinical trials of bubonic plague have been initiated to date (4,5,9), two measure bubo size on at least one timepoint. (4, 9) However, using this data in a clinical and research settings -particularly if it is used to evaluate an endpoint in a clinical trial -is complicated by the fact that there is no validated method for measuring bubo size.…”