The percentage of samples suspected of being incorrectly reported as favorable commonly varied per day and per. Sometimes, the incorrect positive rate rose to 20%. After the intervention, the false positive rate fell to practically no.
He believes the incorrect positives artificially pumped up the COVID-19 case numbers for Belgium. In addition, we just looked at test centers in one part of Belgium, making it hard to get the entire picture.
Scientists at the COVID-19 Federal Platform, Department of Laboratory Medicine UZ Leuven, Leuven, Belgium looked out to the issue in September 2021 after they discovered that 70% of samples that were taken that day at a testing center in Flemish Brabant, Flanders, had evaluated positive for COVID-19. The average positivity rate at the time was around 5-10%.
90% of the positive samples had a very low viral load. This hinted that they had actually been contaminated with the SARS-CoV-2 virus, rather than being real positives.
The clients results were instantly withheld and a root-cause analysis (an investigation into the reason for the spike in favorable samples) was carried out.
Lead researcher Bram Slechten says: “After excluding laboratory contamination we set up the arise from that day in chronological order by time of sample collection.
” We saw that no one had checked negative after a sample was gathered from a patient with a really high viral load and right away called the test center.
” This caused lack of glove-changing, in combination with high-paced sample collection by a new swabber and the breaking of a swab in television, being recognized as the most likely source of the contamination.
” Protocols at this test center were sharpened over night and all the clients whose outcomes were withheld were remembered for a new sample the next day. 100% of them were negative.”
To assess the scale of the problem, Mr. Slechten and coworkers then retrospectively examined four months of outcomes (June-Sept 2021) of PCR tests from 11 testing centers for incorrect positives.
A thought series of infected samples was specified as a minimum of 3 weak positive samples (low viral load, << 104 copies RNA/mL) after one positive sample with a high viral load (>> 106 copies RNA/mL).
They likewise checked out the sites to assess the personnel.
The analysis identified possible cross-contamination occasions in 73% (8 out of 11) of the test centers. The percentage of samples presumed of being wrongly reported as positive extensively different each day and per center. The four-month average varied from 0% to 3.4% per screening.
The highest variety of incorrect positives at one screening center on a single day was 77 (out of 382 tests)– 20% of people evaluated that day. (All of these patients were provided the opportunity to retest.).
Site gos to recognized the absence of glove modifications between patients as being the source of cross-contamination.
” If the staff didnt alter gloves in between each client, it was practically specific that contamination would happen,” states Mr. Slechten. “We recognized four reasons that altering of gloves didnt occur: it was merely not in the procedure; appropriate procedure remained in location but it was not followed due to lack of training of new members of staff; not having the best size of glove offered; work pressure, some swabbers needed to sample one patient every 2 minutes.”.
In response to the studys results, more extensive PPE policies were put in location at all 11 screening centers at the end of October 2021.
This consisted of managers being entrusted with telling every employee who swabbed patients about the value of glove changing and test centers being contacted if there was a spike in their false positive rate.
Occasionally, the incorrect favorable rate rose to 20%. After the intervention, the false favorable rate fell to almost zero.
The team at UZ-Leuven is continuing to keep track of rates of incorrect positives, to identify any separated cross-contamination events.
In addition, Sciensano (the Belgian clinical institute for public health) notified all labs in Belgium to the issue in October 2021.
The scientists say that many of the cases of cross-contamination were found in time to withhold the outcomes and recall the clients, meaning the incorrect results werent offered. Some cases, however, went unnoticed, meaning that on some days, a lot of patients received an incorrect outcome.
Mr. Slechten says: “Nasopharyngeal tasting involves close contact in between the hand of the health expert, the client and sample tube. For that reason, it is important to alter gloves in between each client.
” In the context of high-throughput tasting, insufficiently qualified staff needed to sample high varieties of clients in a minimal time. This situation caused a high level of cross-contamination which had gone mostly unacknowledged, resulting in false positives and individuals taking and self-isolating time off work unnecessarily.
” Furthermore, each false favorable generates high-risk contacts who might also require to be evaluated, increasing the burden for laboratories, screening centers, and contact tracing.”.
He thinks the false positives synthetically pumped up the COVID-19 case numbers for Belgium. He states: “It is tough to put a number on, nevertheless, since we saw a great deal of distinctions between the test centers we studied. In addition, we just took a look at test centers in one part of Belgium, making it difficult to get the entire picture.
” It is very probable that this also taken place in other countries.
” While I dont have detailed understanding of the protocols in testing centers in other nations, the focus is typically on potential occasions within the lab environment. However, our research study supplies a perfect example of the value of looking beyond the lab and watching on the entire testing chain.”.
Absence of glove modifications at COVID-19 testing centers in Belgium led to major cross-contamination of samples and a high rate of false positive outcomes.
A lack of glove modifications at COVID-19 testing centers in Belgium caused significant cross-contamination of samples and a high rate of incorrect favorable results. This was the finding of research that existed at this years European Congress of Clinical Microbiology & & Infectious Diseases (ECCMID) in Lisbon, Portugal.
The introduction of large-scale PCR screening for COVID-19 provided a number of logistical difficulties. A significant one was a scarcity of personnel sufficiently trained to do nasopharyngeal swabbing.
Research study from a government-funded laboratory in Belgium determined insufficient personal protective devices (PPE) management in screening centers as a source of major cross-contamination.
By European Society of Clinical Microbiology and Transmittable Diseases
August 16, 2022
