Missing glove change at COVID-19 test center

Missing glove change at COVID-19 test center

Lack of glove change at COVID-19 test centers in Belgium led to greater cross-contamination of samples and a high proportion of false positive results, research was presented at this year’s European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Lisbon, Portugal, (23 .-April 26) have found.

The introduction of large-scale PCR testing for COVID-19 presented a number of logistical challenges, including the lack of staff adequately trained to perform nasopharyngeal inoculation.

Research from a government-funded laboratory in Belgium has identified inadequate PPE control in test centers as a source of major cross-contamination.

Researchers at the COVID-19 Federal Platform, Institute of Laboratory Medicine UZ Leuven, Leuven, Belgium were warned of the problem in September 2021, noting that 70% of the samples taken that day at a test center in Flemish Brabant, Flanders, had tested positive for COVID-19. The average positivity at that time was about 5-10%.

90% of the positive samples had a very low amount of virus, indicating that they had been contaminated with SARS-CoV-2 virus, rather than being true positive.

Patients’ results were immediately withheld and a root cause analysis (a study of the cause of the increase in positive samples) performed.

Lead researcher Bram Slechten says: “After excluding laboratory contamination, we arranged the results from that day in chronological order according to the time of sample collection.

“We saw that no one tested negative after a sample was collected from a patient with a very high amount of virus, and immediately contacted the test center.

“This led to a lack of change of gloves, in combination with a new high – speed swab collecting samples and breaking a swab into the tube, which was identified as the probable source of the contamination.

“Protocols at this test center were sharpened overnight and all patients whose results were withheld were recalled for a new test the next day. 100% of them were negative.”

To assess the extent of the problem, Mr. Slechten and colleagues subsequently checked the four-month results (June-Sept 2021) of PCR tests from 11 test centers for false positive results.

A suspected series of contaminated samples was defined as a minimum of three weak positive samples (low viral load, <10)4 copies RNA / ml) after one positive sample with a high viral load (> 106 copy RNA / ml).

They also visited the sites to assess the staff.

The analysis identified potential cross-contamination events in 73% (8/11) of the test centers. The percentage of samples suspected of being incorrectly reported as positive varied widely per day and per. center. The four-month average ranged from 0% to 3.4% per year. test center.

The highest number of false positives at a test center in a single day was 77 (out of 382 tests) – 20% of the people tested that day. (All of these patients were given the opportunity to test again.)

On-site visits identified lack of glove change between patients is the source of cross-contamination.

“If the staff did not change gloves between each patient, it was almost certain that contamination would occur,” says Mr. Slechten. “We identified four reasons why it did not happen to change gloves: it was simply not in the protocol; proper protocol was in place but it was not followed due to lack of training of new staff; not having the right size glove available; working pressure, some swabs had to try a patient every two minutes. “

More stringent PPE policies were introduced at all 11 test centers from the end of October 2021 in response to survey results.

This meant that managers were tasked with telling all staff who dried patients about the importance of changing gloves, and that test centers were contacted if there was an increase in their false positive rate.

Follow-up of a test center revealed the effect. Prior to the intervention, it had a daily positivity of 11% and an average false positivity of 3.4%. But occasionally the false positive rate rose to 20%. After the intervention, the false positive rate dropped to almost zero.

The team at UZ-Leuven continues to monitor the number of false positives to detect any isolated cross-contamination incidents.

In addition, Sciensano (Belgian Institute of Public Health) warned all laboratories in Belgium about the problem in October 2021.

The researchers say that most cases of cross-contamination were detected in time to withhold the results and recall the patients, meaning that the erroneous results were not released. However, some cases were undetected, which means that many patients got the wrong result in a few days.

Sir. Slechten says: “Nasopharyngeal sampling involves close contact between the hand of the healthcare professional, the patient and the test tube. Therefore, it is important to change gloves between each patient.

“In the case of high-throughput sampling, insufficiently trained staff had to sample a large number of patients in a limited amount of time. This situation led to a high level of cross-contamination, which had become largely unrecognized, resulting in false positives and people isolating themselves. himself and took unnecessary time off from work.

“Furthermore, each false positive generates high-risk contacts that may also need to be tested, increasing the burden on laboratories, test centers, and contact tracking.”

He believes that the false positives have artificially inflated the COVID-19 case figures for Belgium. He says: “However, it is difficult to put a number on because we saw many differences between the test centers we examined. In addition, we only looked at test centers in one part of Belgium, which made it difficult to get the whole picture.

“It is very likely that this has happened in other countries as well.

“Although I do not have detailed knowledge of the protocols in test centers in other countries, the focus is generally on potential incidents in the laboratory environment. However, our research provides a perfect example of the importance of looking beyond the laboratory and keeping an eye on the entire test chain. “

Bram Slechten, COVID-19 Federal Platform, Institute of Laboratory Medicine, UZ Leuven, Leuven, Belgium T) +32 0470 619905 E) [email protected]

Alternative contact: Tony Kirby at ECCMID Media Center. T) +44 7834 385827 E) [email protected]

Comments to editors:

The authors declare no conflicts of interest.

This press release is based on oral presentation L0503 at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) Annual Meeting. The material has been peer reviewed by the Congressional Selection Committee. There is no full paper at this stage.


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