AHS apologizes after false-positive COVID-19 test at Edmonton hospital

Alberta Health Services is lifting outbreak protocols put in place Saturday at Edmonton's Royal Alexandra Hospital after a false-positive COVID-19 test led to the cancellation of some surgeries and placed the facility on alert.

In a statement to CBC News, AHS said the hospital had been dealing with potential exposure on two units from a patient who initially tested positive for the virus on Saturday.

Outbreak protocols were implemented the same day.

All patients on the affected wards were being tested, contact tracing was being done, some surgeries were cancelled and visitors to the hospital were restricted — until a retest on Monday revealed the patient was not actually infected.

"Two units at the Royal Alexandra Hospital are no longer under outbreak protocol after the one patient who was presumed to be COVID-19 positive, tested negative," AHS spokesperson Kerry Williamson said in an emailed statement to CBC News.

'We apologize'

"We apologize to anyone who was impacted by the postponement of their elective procedures, and we are working to have them rescheduled next week."

False results are uncommon, Williamson said. 

"Unfortunately, on very rare occasions, lab results produce a 'false positive.'"

"When rare errors do occur — and we are made aware of them — results are corrected, the root causes investigated, and corrective actions are taken to further mitigate the risk of such errors recurring." 

Following the false positive test, 13 hip and knee arthroplasty cases and three urogynecology procedures were cancelled.

Those patients will be rescheduled as high priority, as soon as possible, Williamson said.

All emergency and urgent procedures, as well as cancer cases, continued to be scheduled. An additional orthopedic trauma room had been opened to handle any new cases.

Health officials say testing is never 100-per-cent accurate but the tests done at provincial labs exceed regulatory guidelines for accuracy and performance.

"While we do not have a precise measure of the rates of false-negative and false-positive results, we anticipate these results to occur very rarely based on the evaluations that [Alberta Precision Laboratories] has carried out," Williamson said. 

• False negative COVID-19 tests caused by testing too early, faulty swab technique: microbiologist
• Supposed COVID-19 case in Nunavut deemed false positive; top doctor apologizes

There have been several high-profile examples of false-positive tests for COVID-19. A false positive in Nunavut's Pond Inlet came to light in early May and initially had government officials scrambling to get an emergency response team to the remote community.

Dr. Lynora Saxinger, an infectious diseases expert at the University of Alberta, said that with the high number of tests being done, some anomalies are expected. As of Tuesday, 442,253 tests had been completed in Alberta.  

"We've only had this disease and its tests for some months but we've used tests similar to this for respiratory viruses for a long time and false positives are quite rare but not impossible," Saxinger said.

The testing is accurate and sensitive, Saxinger said but like all tests comes with limitations. There is a risk of cross-contamination in the lab or in transport. Another form of coronavirus infecting the patient could also lead to a false positive.

Saxinger said public health officials are more concerned about the possibility of false negatives, which usually result from the improper collection of swab samples. "This just reminds us that it can go the other way too." 

She said Albertans should have faith in the testing protocols, noting that at the Royal Alex, health officials acted quickly to slow possible transmission and were quick to detect the error. 

"It's always better to be safe than sorry with this, because clearly the consequences of the positive when someone who's been in hospital is a big deal and you have to take that very seriously.

"In a way, it means our systems are working the way that they're supposed to."