You seem informed. Are there known rates of false negatives?
Early confirmation can be difficult for detection. Positives seem to be for sure. Negatives in the first days need to be watched for development of symptoms until past 21 days. See below:
When Specimens Should Be Collected for Ebola Testing at CDC
Ebola virus is detected in blood only after the onset of symptoms, usually fever. It may take up to 3 days after symptoms appear for the virus to reach detectable levels. Virus is generally detectable by real-time RT-PCR from 3-10 days after symptoms appear.
Specimens ideally should be taken when a symptomatic patient reports to a healthcare facility and is suspected of having an Ebola exposure. However, if the onset of symptoms is <3 days, a later specimen may be needed to completely rule-out Ebola virus, if the first specimen tests negative.