As the Ebola outbreak simmers on in WestAfrica, researchers have shown the utility of a rapid test for the virus thatcould help contain another epidemic. The ReEBOV test, which needs only afingerprick of blood and gives results in about IS minutes, was grantedEmergency Use Authorization by WHO in February, based on laboratoryasscssments.
Throughout the reccnt Ebola outbreak, clinicians have relied on PCR -basedtests to diagnose cases of the viral disease. The tests require a full vial ofblood to be drawn from a patient's arm and transported to the nearestlaboratory facility-which can take hours or days. In the lab, over the courseof several hours, a PCR machine amplifies the genetic material in the blooduntil there is a sufficient amount to detect. In all, the process can take afew days- during which tine a patient suspccted of carrying Ebola must bequarantined or housed in holding units where they are at risk of infection.
The newer ReEBOV test, currently manufactured by Colorado-based Corgenix, islike the fingerprick tests used by diabetics to test their blood sugar. Withina few minutes after a drop of blood is placed on a paper strip, a line appears signalinga positive or negative result. Unlike PCR-based tests, which look for thepresence of the virus's genetic matcrial, the RcEBOV test detects antigens:protcins made by the body in response to an Ebola infection.
Over a 2-week span in February, researchers used both the ReEBOV test and aclassic PCR-based test on 106 patients who showed up at two clinics in SierraLeone with suspected Ebola symptoms. In addition, the scientists compared thetest’s performances on 284 previously collected blood samples. The ReEBOVantigen test detected every case of Ebola that was diagnosed using theslower PCR-based test, giving it what the researchers believed was asensitivity of 100%. The test also had a handful of false positives, however,making its specificity 92%.
“We weresurprised by the performance," says Nira Pollock, an infectious diseasedoctor at Boston Children's Hospital and an author of the new study.“It wasmore sensitive than I expected for a rapid antigen diagnostic test."
But Polock admits the numbers may be misleading. Afler the collection of theinitial data, the scientists used a second PCR-based test 10 look at some ofthe samples. The PCR test they'd been using as a“gold standard," it turnedoul, wasn't itself 100% sensitive, not only highlighting the discrepancybetween different PCR-based tests but also casting doubts on their new results.In retrospect,“we think we probably overestimated the sensitivity andunderestimated the specificity," Pollock says. More data are neededto illuminatc these numbers, she adds.
A fast, cheap, transportable Ebola test can't come too soon, rescarchers say,"This test can be
done in very austere environments, even off the back of a truck; it doesn'trequire electricity or a sophisticated lab or an experienced technician,"points out Robert Garry, a virologist at Tulane University in New Orleans,Louisiana, who helped develop the technology the test is based on but was notinvolved in the new trial.
What is the passage mainly concermed with?
A.The RcEBOV test made in West Africa B.The PCR-based test C.The fingerprick test D.How to diagnose the Ebola正确答案C
