The scientific and technical staff at WSCL have been very busy! There were times of intense testing activity, both from testing in our region, and from helping at times with Auckland tests. In this newsletter we provide some information about what is going on.
Volumes
To date Wellington SCL has performed 300,000 COVID tests.
These two graphs show the huge number of being processed as a result of the recent Auckland outbreak. These numbers were achieved by pooling community specimens and redeploying staff to cope with registering, unbagging, pooling, testing and reporting specimens and results. In addition to the Wellington Hospital Lab, we also run tests at Hutt Hospital and at Gribbles in Palmerston North at peak times.
Tests and specimens
Nasopharyngeal swabs are by far the most common sample, but we are processing increasing number of saliva samples, for border workers and permitted workers crossing COVID alert level boundaries. It appears that when given the choice, only 10-20% of frequently tested people prefer saliva.
We have a number of different testing platforms which are used according to urgency and priority of testing
Point of Care Tests in all Hospital Emergency Departments for urgent rule-out tests in low risk persons. These use similar technology to PCR but are not quite as sensitive as a lab PCR test. They need a nasopharyngeal swab.
GeneXpert PCR. These rapid PCR tests are in short supply internationally and are reserved for high priority tests that need a result within 2 hours. They are used mainly in hospital and for critical Public Health tests
Other PCR tests. These have a range of cool names including Kingfisher, Panther, Roche 6800, and are suited for high through put testing with a 4-6 hour run time. Either saliva or NPS are suitable.
In mid October Wellington SCL will implement our new throughput Roche 6800 analyser which will double our regional COVID testing capacity.
Serology. We have tests that can test antibodies that are associated with vaccine (or infection) related immunity, and those associated with infection. They have been of most use for pretravel clearance and for timing of infection.
Turnaround times
Often the slowest part of the process is transport to laboratory, and we are proud of our median test turnaround time of 5.7 hours from arrival into the laboratory. Unless there is a large peak, almost all results are back within 24 hours. This is evidence of the great team work by all the staff from transport, reception, pretesting, testing and reporting.
What’s next?
We are preparing for the next phase when the borders (internal and external) open because sufficient vaccine coverage has been achieved. We will see an even greater reliance on testing and expectation that people with COVID will self isolate.
It is likely that self-tested antigen tests will become used when the sensitivity (70% compared to PCR) is not so critical, as a way of performing perhaps 100,000 tests per day across NZ. We are not at that stage yet, and we would not consider antigen tests reliable enough for excluding COVID infection. However, we are likely to see them soon as a “sieving” technique to rapidly identify some positive people, preferably before they get near a hospital.
Dr Tim Blackmore
Clinical Microbiologist
Wellington SCL
