Rako Science is reporting a 99% sub 24-hour total turnaround time for 10,000 randomly selected October COVID-19 PCR saliva tests. The mean total turnaround time was 10 hours and 6 minutes. Total turnaround time starts from moment of sample provision and ends with release of results. Rako Science also randomly selected 250 urgent tests and the mean turnaround time was 4 hours and 15 minutes.
In medical diagnostic testing the time between the sample being received in the laboratory and the issue of the authorised result is called the Turnaround Time (TAT). TATs are used as quality performance indicators to ensure that laboratory results are released in a timely fashion. However, during a pandemic the TAT becomes much more than a performance indicator. It becomes a critical component in the health response and to knowing and understanding exactly how far and fast the virus is spreading. A recent news article highlighted some issues in the public health laboratory network with TAT.
Within the public health laboratory network, 80% of the COVID-positive test results are required to be available within 24 hours and the expectation from the Director General, as indicated in a recent interview, was that all positive results would be received within 48 hours. This enables positive cases to be identified, notified and isolated and to allow contact tracing to occur in as short a time frame as possible. There have been recent examples in the media of TATs for positive cases exceeding 5 days, which is well beyond what is required and desired.
It is important too that we appreciate the sheer number of tests that this equates to. Of the 152,763 tests taken last week, 41,246 were resulted beyond the 24 hour “gold standard”. When you are dealing with Delta, this is simply not good enough. Laboratory staff across the country are tirelessly working to try and maintain this standard, but the systems and resources are quaking under the strain. As testing numbers increase, as they are and will, keeping within this timeframe becomes an almost impossible task. The greater the number of samples that fall foul of this yardstick, the greater the chance that positive samples lie amongst them. This is not a criticism of the laboratory workers but an indication of the sheer volume of testing that is being undertaken.
This is also very concerning given that those suspected of COVID and close contacts with a “high degree of suspicion” are ear-marked as “urgent” at the time of collection in an attempt to maintain the 24 hour TAT. If only a proportion of these urgent samples are within the designated turnaround time, one must be concerned about those that are not selected for more speedy processing. Given the volumes of samples being tested at present, it is quite possible that a positive case could be amongst the “likely negative” samples that do not on the face of it require expedited processing. This being the case there is an increased chance that an unknown, unlinked positive is there amongst them.
There is no definition provided for turnaround time in ISO15189 (the international standard that laboratories are measured against for accreditation). It could be interpreted as from the time the samples are received by the laboratory to the issue of results or from the time of sample collection to the receipt of results. In Table 1, the Laboratory Turnaround Time (LTAT) and the Total Turnaround Time (TTAT) are defined in terms of the processing of a medical test from the time the test is collected through to the time that the results are received.
Stages of a medical Test | LTAT | TTAT |
Sample Collection | Yes | |
Transportation | | Yes |
Receipt in Lab | Yes | Yes |
Analysis | Yes | Yes |
Interpretation | Yes | Yes |
Reporting | Yes | Yes |
Authorisation | Yes | Yes |
Release of result | Yes | Yes |
Receipt of result | Yes |
Table 1: Components included in calculations of Laboratory Turnaround Time (LTAT) and the Total Turnaround Time (TTAT)
LTAT has been previously discussed and does not need to be laboured. Briefly, Figure 1 shows that for 10,000,randomly selected, saliva samples processed through Rako Science during the month of October the mean LTAT was 4 hours and 48 minutes.
Figure 1: LTAT Mean LTAT 4 hrs 48 mins (CI 95% 4 hrs 46 min – 4 hrs 50 min)
In this blog we focus on the TTAT because that is the metric of critical importance during a pandemic when you are trying to achieve suppression and containment.
Rako Science has been operating scale testing in the private market in parallel to the laboratories in the public health laboratory network since January 2021. For 10,000,randomly selected, saliva samples processed through Rako Science during the month of October the TTAT has been calculated (Figure 2).
Figure 2 - Total Turnaround Time (TTAT) for the Rako Science Saliva Test for 10,000 randomly selected tests in October. The mean total turnaround time is 10 hrs 6 minutes (CI 95% 10 hrs 2 min – 10 hrs 10 min). Only 1% of the samples, shown in red, exceeded 24 hours set by Dr Ayesha Verrall as the gold standard for the public health laboratory network
The data shows that the mean TTAT for the Rako Science saliva test was 10 hours and 6 minutes. 99% of Rako Science saliva test results are received within 24 hours of sample collection. The 1% of cases that are resulted outside of 24 hours are due to circumstances beyond the laboratory as demonstrated by the LTAT (Figure 1) which showed that 100% of samples are resulted within 24 hours of arrival in the laboratory.
Dr Ayesha Verrall states that:
“Some of the recommendations of my report around the timeliness of certain measures wouldn't be suitable for Delta”.
That is indeed correct, they need to be shorter! The sooner that a positive case is identified, the sooner that they can be isolated and contact tracing can begin.
We also examined those samples that were specifically processed as urgent during the same time frame (Figure 3).
Figure 3 Urgent Total Turnaround Time (UTTAT) for Rako Science Saliva Test for a sample of 250 urgent randomly selected tests in October. The mean UTTAT was 4 hrs 15 mins (CI 95% 4 hrs – 4 hrs 30 mins).
A sample of 250 urgent randomly selected tests (UTTAT) in October show the Rako Science saliva test has a mean of 4 hours and 15 minutes. The standard deviation of urgent tests is 1 hr 54 mins.
Our data demonstrates that it is possible for the TTAT to be much less than 24 hours for almost all samples. It is also possible for urgent results UTTAT, using the same processing methods, to be available in just over 4 hours from time of collection.
At a time when the number of positive cases is soaring in Aotearoa New Zealand and compliance with restrictions is waning, we need to have the most sensitive test possible with a consistent turnaround time of less than 24 hours. The only way for this to be achieved is to have a testing regimen that is designed for high capacity with short TATs. The Rako Science saliva COVID-19 test is just that – highly sensitive, accurate and fast. At this stage in the battle against COVID, we cannot afford for even one positive result to take longer than 24 hours to be notified to the public health authority. With Delta every second counts!
 | Dr Amanda Dixon-McIver Amanda Dixon-McIver is the Laboratory Director of IGENZ, the IANZ-accredited medical diagnostic laboratory contracted by Rako Science to perform the COVID-19 saliva testing at scale. She has 30 years of laboratory experience both here in Aotearoa New Zealand and overseas and has been involved in the NZ laboratory response to COVID since the start of the pandemic in 2020. |