Kenneth, we are concerned about false negatives...not false positives...
Ebola Test Gives False Negatives
Posted on October 6, 2014 by WashingtonsBlog
Why It’s Important to Do Multiple Tests On Suspected Ebola Victims Before Releasing ThemNewsweek notes:
On July 15, Omeonga’s boss walked into his office at St. Joseph Catholic Hospital in Monrovia, Liberia full of worry. The hospital director told Omeonga he had shaken hands with a man who was later diagnosed with Ebola, and now he was feeling ill—the director had been vomiting, had a headache, and was running a high fever. But two days later, when the diagnostic test came back negative, that worry was banished, and Omeonga and his colleagues began caring for the director as they would a typhoid or malaria patient. “We wore gloves, but we were not very strict at all.”
A week later, the director’s symptoms got worse, and he was tested again. This time, it came back positive for Ebola—the first test was a false negative [i.e. the test erroneously showed that the person did not have Ebola, when he did]. Suddenly, everyone who had cared for him was a possible Ebola case. The hospital became a quarantine zone. The director died on August 2, the same day Omeonga began to feel sick. Of the 20 health workers who had been in contact with him during that week, 15 came down with Ebola a short while later, including Omeonga. Nine of Omeonga’s colleagues died. He and five others survived.
It’s not just tests done in Africa which may be problematic …
According to American authorities, the PCR test is the “gold standard”. As Emory University notes:
The gold standard of testing for the Ebola virus in the United States is the Centers for Disease Control and Prevention (CDC) RT-PCR assay, which was used by Emory physicians in deciding when to discharge two patients from Emory University Hospital.
CDC Director Tom Friedan said last week:
Testing for Ebola is highly accurate. It’s a PCR test of blood.
But the Journal of Clinical Microbiology noted in 2002 that the PCR test can yield false negatives for viral hemorrhagic fevers such as Ebola:
A confirmation by PCR would have been missed if we had not tested a duplicate sample.
And the U.S. Department of Defense noted in August (on page 2):
The possibility of a false negative result should especially be considered if the patient’s recent exposures or clinical presentation indicate that Ebola Zaire virus infection is likely, and diagnostic tests for other causes of hemorrhagic illness are negative.
It is essential that Ebola tests be run more than once before any suspected Ebola victims are released. |
