It was overuse of acetaminophen that ultimately led to Nic Petermann’s cancer diagnosis. For months, the then 26-year-old had struggled with exhaustion, night sweats, recurring fevers and abdominal pain so debilitating that she regularly woke up in the middle of the night to take soothing baths. His persistent flu-like symptoms, he had read online, were likely just the lingering effects of a Covid infection he had in January 2021; pain was an odd symptom, but an ultrasound had found nothing.
By June, the pain was too much to bear—Petermann called a hotline and was immediately referred to the hospital after staff learned how much acetaminophen she had been taking. After extensive testing, Petermann finally had an answer: All of his symptoms, including what appeared to be Covid-long symptoms, were due to stage IV Hodgkin’s lymphoma. Chemotherapy started the next day.
Today, Petermann is in remission, although he still faces the long-term consequences of months of aggressive chemotherapy. If he hadn’t assumed most of his symptoms were due to prolonged Covid, he says, he might have received the right treatment and diagnosis much earlier. “When I went to check my pain symptoms, I didn’t mention the flu-like symptoms, because I just thought it was something I would have to deal with,” she says.
Most people with Petermann symptoms will not end up in his position. Long-lasting Covid is common: estimates of its prevalence vary widely, but even the most conservative studies imply that millions of people suffer long-lasting symptoms from their infections. Hodgkin’s lymphoma, on the other hand, is rare. But with dozens of possible symptoms, long-term Covid can easily be confused with many other conditions, including cardiovascular diseases such as hypertension and diabetes, autoimmune diseases such as lupus and multiple sclerosis, and cancer. Add to that the fact that Covid can make pre-existing conditions worse and determining whether or not someone has had Covid for a long time becomes a daunting task.
Analyzing these broad sets of alternatives has become the responsibility of doctors on the front lines of long-term Covid care, from the primary care doctors that patients seek first to the experts working in long term covid clinics. For each patient they must perform an accurate differential diagnosis, a medical term for the process of considering all the possible causes of a patient’s set of symptoms.
Accurate differential diagnosis is essential not only to obtain care for patients, but also to improve medical understanding of a still obscure condition. “We have to be careful not to make long-term Covid-19 a global diagnosis,” says Linda Geng, co-director of Stanford’s Post-Acute Covid-19 Syndrome Clinic.
In the absence of objective evidence, however, Covid remains a “diagnosis of exclusion”, which is only made after other reasonable possibilities have been exhausted. Recent data suggests that many patients will emerge from this process with a diagnosis not of long-term Covid, but of something else. A July newspaper Nature which looked at the medical records of more than 2 million patients in the UK found that while 5.4 per cent of those with a previous Covid infection had at least one prolonged Covid symptom recorded in their charts, 4 .5 percent without Evidence of infection also had at least one symptom.