Test after test has been administered here in America and many have come back negative from New York, to DC, to Hawaii. But the thing is are these negatives really negative or do they have a chance of being a false negative? Is it even possible for an Ebola test to come back wrong?
While I do believe all the tests in America thus far have been correct, we unfortunately are not being told all the details about this raging virus. One minor detail is being purposefully left out and that is the nature of scientific assays for the disease.
This has left many believing the misguided impression that when an Ebola test comes back negative, that it is 100% accurate…..
The sensitivity of an assay measures the likelihood that the assay produces a positive result when the subject is in fact afflicted (true positive). The specificity of an assay measures the likelihood that the assay produces a negative result when the subject is in fact not afflicted (true negative).
Each of these in turn has a complement. The complement of true positives is false positives, while the complement of true negatives is false negatives. False negatives are results where the subject is afflicted but the test says they’re not.
Since false negatives are the complement of specificity, if the specificity of a test is 95%, the false negative rate is 5%.
Clearly, the prospect of false negatives in an Ebola setting is one of grave concern.
One test for Ebola, the indirect fluorescence assay, is known to have a rather low specificity, and therefore a rather high false negative rate. PCR testing has also been known to miss cases of affliction.”
Statistically speaking the more Ebola patients we have, the more likely we are to come across a false negative, if not a few false negatives. Either way, we need to do our best and prepare!
“The situation is worse than it was 12 days ago. It’s entrenched in the capitals. Seventy percent of the people [who become infected] are definitely dying from this disease and it is accelerating in almost all settings,” Bruce Aylward, assistant director general of the World Health Organization
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