There is good reason to believe that one of the primary reasons
for the initial spread of Ebola in this West African outbreak was
improper laboratory testing procedures (see Chronology
of the Ebola
Outbreak in West Africa).
Laboratory testing is crucial in an Ebola
epidemic. Clinicians rely heavily on it in determining who is isolated
and treated as a confirmed Ebola case and who gets sent back into the
general population. The lab test is also the final arbiter of those who
have officially survived Ebola, are no longer infectious and can be
sent back to their communities. The lab test even determines the fate
of the dead. An Ebola corpse is highly infectious and must be buried
without delay and with elaborate safety precautions. A non-Ebola corpse
can be buried with observance of normal funeral rites. In Sierra Leone
during this epidemic, all deaths that occur outside hospitals are
considered potential Ebola cases; families are required to obtain an
Ebola status certificate after a swab/lab test before burial.
Ebola testing laboratories are under a considerable amount of pressure.
There is great time sensitivity surrounding the outcome of their tests.
If doctors do not receive test results speedily, patients have to be
kept for long periods in holding centers, subject to cross infection
with others in these centers. If the status of the dead is not declared
speedily corpses begin to rot in homes, spreading infection and causing
great unease in the community. As the epidemic has mushroomed so has
the demand for tests, and the laboratories have at times been hard
pressed to meet the demand. At first in Sierra Leone there was just the
one Ebola laboratory, in Kenema, then a second run by the Canadians in
Kailahun, then a third, South African, lab in Freetown, a fourth,
Chinese, lab, also in Freetown and now a fifth, CDC, lab in Bo.
All tests are subject to error. The Ebola test, in particular, is said
to be highly sophisticated and sensitive. From the regular Sierra Leone
Ministry of Health updates we know that some patients have to be
retested, when their clinical symptoms conflict with the lab test
result. Errors in tests could be divided into two broad categories:
false positives and false negatives. Both are problematic. The false
positive test result incorrectly labels a patient who does not in fact
have Ebola. This patient would then under normal circumstances be sent
to an Ebola treatment center, where he/she would be at high probability
of going on to actually become infected with Ebola. So the false
positives end up killing patients who otherwise would probably have
recovered from whatever ailment they had.
The false negative test result, on the other hand, incorrectly labels a
patient who does in fact have Ebola. Under normal circumstances this
patient is then sent back to a general ward or released to his/her
family. In either case all those in close, unguarded contact with the
patient will be liable to Ebola infection. In the case of highly
infectious Ebola corpses, the false negative exposes mourners and those
preparing the body for burial to the disease.
With so many labs in Sierra Leone from different countries and under
such pressure, is there a need for independent testing of the testers?
Is our Ministry of Health checking for consistency of test results
within each lab and across all labs? Already one hears rumors within
the public as to which labs are doing the ‘real’ tests and which are
not. Experience from earlier in this outbreak teaches us that if even
one lab is delivering a significant percentage of false results this
could be disastrous for the course of this outbreak.