Haemostatic Changes in Five Patients Infected with Ebola Virus

Abstract

Knowledge on haemostatic changes in humans infected with Ebola virus is limited due to safety concerns and access to patient samples. Ethical approval was obtained to collect plasma samples from patients in Sierra Leone infected with Ebola virus over time and samples were analysed for clotting time, fibrinogen, and D-dimer levels. Plasma from healthy volunteers was also collected by two methods to determine effect of centrifugation on test results as blood collected in Sierra Leone was not centrifuged. Collecting plasma without centrifugation only affected D-dimer values. Patients with Ebola virus disease had higher PT and APTT and D-dimer values than healthy humans with plasma collected in the same manner. Fibrinogen levels in patients with Ebola virus disease were normal or lower than values measured in healthy people. Clotting times and D-dimer levels were elevated during infection with Ebola virus but return to normal over time in patients that survived and therefore could be considered prognostic. Informative data can be obtained from plasma collected without centrifugation which could improve patient monitoring in hazardous environments.

Keywords: APTT; D-dimers; Ebola virus; PT; clotting; fibrinogen; haemostasis.

Figure 1

Effect of collection method on four haemostatic parameters. Naïve blood samples were collected from healthy UK volunteers and analysed for Prothrombin Time (PT), Activated Partial Thromboplastin Time (APTT), fibrinogen, and D-dimer amounts. Plasma was obtained by centrifugation (standard method) or by non-centrifugation where blood was left to separate over time. Non-centrifuged plasma was collected for comparison with Ebola virus-infected plasma samples collected without centrifugation. Each test was run in duplicate and both values are shown. For some centrifuged samples, multiple aliquots from the same donor were analysed on different occasions, each individual result is also shown. Mean and SEM (coloured lines and bars) are shown for each data set. Unpaired t-tests were performed to compare the results from the two collection methods.

Figure 2

Changes in haemostasis parameters over time in Ebola virus-infected individuals. Mean values of Prothrombin Time (PT), Activated Partial Thromboplastin Time (APTT) (top row) and fibrinogen, and D-Dimer values (bottom row) from plasma samples collected without centrifugation from five patients are shown. Each time-point was tested in at least duplicate and mean plotted. Each patient is represented by a different colour and symbol and days of sampling post-symptom onset were different for each patient. Grey shaded area indicates the range of values for each test obtained from naïve ‘normal’ human donor samples also collected without centrifugation (Figure 1). Dashed line is the mean value from the un-centrifuged non-infected samples and the dotted line is the value of the un-centrifuged mean + 3 standard deviations (for fibrinogen—3 standard deviations also shown with a second dotted line). If data distribution is approximately normal, then 99.7 % lies within three standard deviations. One PT result and several D-dimer results were out of range and are plotted at the upper limit of the test and indicated as such for each data set.