New research from the United States suggests Long COVID may have affected fewer people for less time than previously thought.
Using refined data collection methods, a team from Stanford University has found that people suffering from chronic COVID-like symptoms may have been misdiagnosed or the illness overreported.
According to the Australian government, Long COVID is defined as contracting COVID-19 and experiencing symptoms for a period of at least 12 weeks afterwards.
But researchers said no clinical test exists for Long COVID, making it difficult to track its prevalence accurately.
They stress that people who were wrongly assumed to have Long COVID may still have experienced debilitating symptoms that could have been caused by other illnesses.
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"These findings indicate that Long COVID may be more similar to other extended post-viral syndromes than many have thought," said co-author Steven Goodman, professor of epidemiology and population health in the Stanford School of Medicine.
The Australian government predicted there would be more than 1.3 million cumulative historical Long COVID cases nationwide by the end of 2023 and suggested between 5-10 per cent of people who contract COVID-19 still have symptoms after three months.
The Stanford researchers reviewed 4.4 billion health insurance records from more than 244 million Americans and say they found a flaw in previous studies.
Older research compared people who tested positive for COVID-19 with people who were never diagnosed or tested.
The issue is that people who are more likely to test also have more records of various health issues, which can create a biased association between those health issues and COVID-19.
Professor Jure Leskovec, another author of the study, explained these discrepancies may substantially overestimate the range and duration of health effects attributable to COVID-19.
"Our new study design found 98 per cent fewer Long COVID-attributable outcomes between four to 12 months after infection compared with conventional approaches applied in the same dataset," he said.
"This doesn’t mean Long COVID is 98 per cent less common. It means that how we design these studies fundamentally changes which health effects we can reliably attribute to COVID."
By focusing only on patients who tested positive or negative, the researchers believe they have produced a more accurate picture of COVID-19's long-term health effects.
Professor Paul Griffin from the University of Queensland School of Medicine told SBS News refining our understanding of Long COVID is vital for supporting people with the illness.
"We need to make sure that we continue to look into Long COVID, manage those people, try and find tests and obviously also therapies to try and improve their situation," he said.
No diagnostic test exists for Long COVID, and Griffin explained that the criteria some experts use have shifted over time.
It's suspected there could even be different forms of Long COVID, further complicating both diagnosis and treatment.
"It's a complex constellation of symptoms that can involve pretty much every organ system in the body," Griffin said.
The disease can also manifest differently in people or be confused with other illnesses with similar symptoms.
In the worst case, some patients may have their symptoms dismissed or discounted because there is no reliable test.
"They may see some clinicians who say that they don't have anything wrong with them or that it might be due to something else or perhaps it's psychological and not an actual condition relating to their COVID infection."
Without a reliable test, some Long COVID cases could be underreported, which could mean inadequate resources are directed toward the condition.
"For a short period of time there were some resources deployed to help address that. But then I think in more recent times, a lot of those have been wound up," Griffin said.
Australia has only a handful of Long COVID clinics run by hospitals or GPs.
Dozens more of these clinics and targeted support programs have been discontinued since the height of the pandemic.
Experts said scientists worldwide will keep improving their understanding of the COVID-19 pandemic, both to better understand its impact and to prepare for future public health emergencies.
"COVID-19 had been one of the worst pandemics we face, but it certainly won't be the last. We can take the opportunity to reflect, see how we can be better prepared, and I guess also continue to manage COVID well," Griffin said.
Scrutinising and refining statistics is therefore part of building population wellbeing and resilience.
Leskovec said: "These results should complement physicians’ clinical assessments, not replace them."
"On the other hand, for data scientists, earlier Long COVID studies might need to be revisited with better controls. Our approach could improve those and future population-health studies."
