Is LTC screening worth it?
An Ontario expert panel concludes it is not but their reasoning is odd.
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According to a new Science Table report in Ontario, long term care (LTC) testing isn’t worth the bother any more. From The Globe and Mail:
There’s no evidence that routine asymptomatic COVID-19 testing prevents outbreaks in long-term care homes, a new brief from the Ontario COVID-19 Science Advisory Table says, noting the potential harms of using these tests to screen staff likely outweigh the benefits.
In its brief, released Tuesday, the science table found asymptomatic screen testing of Ontario’s long-term care staff identified relatively few positive cases. Yet these tests are costly, place a burden on the province’s labs, risk exacerbating staffing shortages, and can cause pain and discomfort to staff who undergo repeated testing, it said.
“We know that overall, the yield of this testing has been quite low, and we know that there are several direct and indirect harms and opportunity costs of this testing,” said Toronto geriatrician Nathan Stall, a member of the science table who co-wrote the brief.
That seems … odd. The argument is that testing is not picking up many cases and so the benefits are much lower. We normally are trying to get positivity rates down (that is the whole goal of asymptomatic testing — to drop the number of positive cases amongst those being tested to a level where we are confident we are getting good information). But here an expert panel is saying that it is dropped so far that testing isn’t worthwhile any more.
Here is the relevant graph:
There is a big difference but the reason why is that staff at LTCs are being screened every one or two weeks whereas that is not true for the population.
In Ontario, a total of 705,370 SARS-CoV-2 tests were performed on asymptomatic LTC staff between June 28, 2020 and March 13, 2021 which yielded 1,147 positive results (0.16% test positivity). Overall test positivity rates ranged from <0.1% during times of low SARS-CoV-2 incidence (weekly incidence rate <10 per 100,000, in accordance with Ontario’s colour-coded COVID-19 response framework) across the Province of Ontario, increasing to a peak of 0.36% during times of very high incidence (weekly incidence rate ≥40 per 100,000, in accordance with Ontario’s colour-coded COVID-19 response framework)12 (Figure 1). These Ontario findings align with multiple Canadian and international studies demonstrating a <0.5% positivity rate in asymptomatic individuals tested for SARS-CoV-2 in low incidence settings (COVID-19 Provincial Diagnostic Network Laboratories, personal communication).
That sounds like they prevented over 1,000 potential outbreaks which ain’t nothing. These are PCR tests which the report notes were often coming in with results a day or so later which, as we all know, is why you want rapid screens instead. But is there any reason to suppose that the benefits of testing have changed so dramatically?
The report points to vaccinations. With staff being vaccinated, there is less reason for testing. But the report doesn’t say what to do with staff who haven’t been vaccinated let alone others who might come into a facility. This doesn’t seem like a reason to drop to nothing.
The report then details the costs of testing. First, they argue that there are false positives which are more of a problem when prevalence is low. But then they don’t tell us how many false positives there actually have been despite saying the PCR tests have a high specificity (which they do). The report just says that false positives lead to costs. Moreover, with a third wave upon us in Ontario, our concern about false positives goes down, not up.
Second, there is the discomfort associated with PCR testing. No one likes those long nasal swabs but that is what they were doing. OK so how about not doing that? The report considers rapid antigen screens as an alternative but makes the following claim:
Rapid antigen testing has the benefits of being much less expensive than RT-PCR and more comfortable as it is more commonly collected with a combined swab of throat and both nares or a deep nasal swab rather than with a nasopharyngeal swab. Additionally, by providing nearly immediate results, rapid antigen testing can address the issue of test turn-around times. This comes, however, at the cost of lower test sensitivity, requiring an increased testing frequency of 2-3 times per week in high SARS-CoV-2 incidence regions and once per week in low SARS-CoV-2 incidence regions. The LTC staff resources needed to operationalize the rapid antigen testing strategy is much higher than with RT-PCR, with estimates of each home requiring an additional two full-time employees required for implementation. Thus the reduced costs of rapid antigen testing associated with eliminating laboratory needs is offset by much higher health human resource costs in LTC homes. Ontario’s proposed transition to rapid antigen testing comes at a time when staff shortages within the LTC sector are already extremely high, with serious concerns about whether homes will be able to hire new employees, or whether this strategy will draw from existing strained resources, and thus potentially negatively affect resident care.
The argument is that it is actually harder to conduct rapid antigen screens than PCR tests for the homes themselves. This seems odd. They then go on:
The practicality of thrice-weekly rapid antigen testing is also challenging, as it takes roughly 20-30 minutes for the entire testing process, and sufficient time and space are needed to allow staff to maintain physical distance from each other while tests are being processed to avoid SARS-CoV-2 transmission. Time spent undergoing testing may reduce time spent with residents, which may further compromise LTC staffing and care.
I won’t deny that there are costs associated with regular screening. But what we have found at the CDL Rapid Screening Consortium is that those costs are much, much lower than what this panel seems to believe they are. The time taken to get a swab from someone is a minute. There is time to process the result. However, unless you are operating a tight bubble — which Ontario LTCs were decidedly not — then that doesn’t matter. You notify the person when the result comes in. No need for staff time to be sucked up at all.
Thus, the report dismisses rapid antigen screens as a cost-effective alternative based on presumption rather than study. Everything “medical” is well documented but apparently, when it comes to the “managerial” the panel is satisfying claiming assertions as fact.
Those assertions matter. That claim was reported in the press. It is simply false. If you just follow Ontario’s rapid antigen screening guidelines, that it is false is already understood.
Here’s the thing: LTC facilities are the riskiest places around. Vaccinations will help that but will they do so perfectly enough? Will residents and staff all be vaccinated? I doubt that will be possible for medical reasons alone. That means the panel is arguing to go from regular testing to nothing without considering intermediate protective steps.
What’s more, of all the evidence presented, they do not actually look at the record on outbreaks in LTC in Ontario since a testing regime was put in place in July 2020. But their own earlier report provides that. Here it is:
That report does not suggest one bit that testing is not a factor — in fact, in my read it suggests the opposite. That said, there was much going on.
This suggests to me that this conclusion:
There is no available real-world evidence to either support or refute the benefit of routine asymptomatic screen testing in preventing COVID-19 outbreaks. Screen testing among Ontario LTC staff between June 28, 2020 and March 13, 2021 yielded an overall test positivity of 0.16%, which decreased to <0.1% during periods of low SARS-CoV-2 community incidence. Given the high rates of protection of COVID-19 vaccines against SARS-CoV-2 infection and emerging evidence for prevention of transmission, asymptomatic routine screen testing is likely of low yield in vaccinated staff outside of an exposure, or outbreak setting. The potential harms and opportunity costs likely outweigh the benefits of ongoing screen testing among vaccinated LTC home staff, even when B.1.1.7 is the dominant SARS-CoV-2 variant.
… is not warranted or supported by their own arguments. Instead, at best, there is reason to pursue a changed policy with more cost-effective targeting. It seems to me that it is just too risky to go from doing something to nothing on the testing front.