Lancet delivers key details on a rapid new Ebola test; quantifies sensitivity/specificity and explores study limitations
Rating
New rapid diagnostic test for Ebola could be game changer in the fight against the disease
Our Review Summary
This release from the The Lancet plays up a first-of-its-kind rapid diagnostic test for Ebola virus disease (EVD). We’re told the ReEBOV Antigen Rapid Test (made by Corgenix) could be a powerful future tool in detecting, monitoring, and controlling outbreaks of EVD. The excitement stems from a recent field study conducted during an Ebola outbreak. After that trial, the release explains, clinicians found the test to be faster than and as reliable as the current standard method for detecting EVD, called real-time reverse transcription polymerase chain reaction (RT-PCR). The release helpfully quantifies both the sensitivity and specificity of the test, giving readers a thorough overview of the test’s performance both in identifying cases of Ebola and ruling it out in people who don’t have it. What’s more, the release tells us, the new rapid-diagnostic test requires just a drop of blood instead a vial of blood, and takes minutes to get a result instead of days.
The new test sounds like a potentially critical new tool in rapidly diagnosing EVD, but it has strings attached. The release does disclose these caveats — e.g. the test missed some early cases, it requires refrigeration, and it’s ability to detect EVD early on is limited. Our wish list for this otherwise very complete release includes context about how deadly EVD is and how it’s transmitted; what the symptoms are; what regions its endemic to; etc. We’d also like to know a bit about the regulatory side of things — which of these tests have been approved, and what are the roadblocks to approval/bringing the test to the field?
Why This Matters
On average, the Ebola virus kills about half of the people it infects. Recent outbreaks in Africa have claimed tens of thousands of lives. Although standard diagnostic tests take hours to process, it might take days for samples to reach a lab from remote places where an outbreak is happening. In addition, there have been reports in Guinea of potentially infected individuals not wanting to travel for testing due to a cultural mistrust of authority figures. So any fast and reliable diagnostic test — especially one requiring only a finger prick — could help workers on the ground detect and control the spread of an outbreak, as well as reduce the risk of infection to themselves (since Ebola virus spreads through bodily fluids).
Criteria
Not Satisfactory
We don’t see any dollar signs in this release, either for the new test or RT-PCR. According to a New York Times blog post, they cost $60-$200 each.
Satisfactory
The release dedicates two paragraphs to describing the results, including comparing them to standard tests made by two different companies. We were particularly pleased to see reporting on the sensitivity and specificity of the test, as well as descriptions of what those numbers mean. We think those figures are important to include in any discussion of screening or diagnostic testing, but they’re often not provided or reported incompletely.
Not Satisfactory
The release explains how not having a rapid-diagnostic test could expose people who are otherwise healthy to Ebola. But there are some less obvious harms this release probably should have addressed. For example, there’s only brief mention of how the new test missed some early cases of EVD. Waiting a few minutes for a result is better than hours or days, of course, but letting infected patients with a false-negative test out of quarantine is a serious concern. It would also be useful to talk about the impact of a false-positive result (since specificity was 92%). What are the consequences of telling someone they have Ebola when they don’t, in fact, have the infection?
Satisfactory
The release runs through key statistics with the efficacy of the new test. It also discusses its shortcomings, attaches numbers to those, and discloses that further testing is required to better understand the limitations.
Satisfactory
No excessively scary descriptions of Ebola virus infections are anywhere to be found. But because the release didn’t include any general information about EVD, it has an opposite problem — a journalist might not grasp the scope and urgency of controlling outbreaks, and how intimately a new test might play a role. For example, few understand that there continues to be widespread transmission that is poorly controlled in Guinea in particular. We’ll rate this Satisfactory with reservations.
Satisfactory
We’re told the Abundance Foundation funded the test and the maker of the rapid-diagnostic test, Corgenix, provided the kits.
Satisfactory
This is definitely a strong part of the release — the new test is compared to two manufacturers’ versions of the standard RT-PCR test. But the release doesn’t mention other diagnostic tests, including virus isolation and ELISA.
Satisfactory
We’re told the following, via a quote from a researcher: “Although the RDT requires refrigeration, this is already available in many health centres in endemic areas, particularly those that store vaccines and other medical products.” Although we’d like to know more about the regulatory approval status of the test, we’ll award a Satisfactory here.
Satisfactory
The release does a fine job of establishing novelty: this new test takes minutes instead of what might take days; results can happen on-site; it only takes a few drops of blood from a finger instead of a vial’s worth by vein.
Satisfactory
There are a couple of points of contention here. The term “game-changer” used in the headline is rarely justified, but we think the release provides the evidence to show that this test could, in fact, be a game changer. In addition, we’re not sure that the test is “as sensitive as a conventional laboratory-based molecular method used for clinical testings.” In reality, it did as well as one manufacturer’s test in the field, but worse than another’s. But we’re inclined to give this a Satisfactory rating, since the rest of the release is well-hedged and caveated.
Total Score: 8 of 10 Satisfactory
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