The study, conducted by King’s College London, analyzed data from about 1,600 UK and US coronavirus patients who regularly logged their symptoms into a tracking app in March and April.
The findings revealed that six distinct groupings of symptoms emerge by the fifth day of the virus’ progression, which the researchers say could help doctors better treat individual patients by allowing them to predict what level of hospital care they need.
“Our study illustrates the importance of monitoring symptoms over time to make our predictions about individual risk and outcomes more sophisticated and accurate,” said lead researcher Dr. Carole Sudre from King’s College London.
“This approach is helping us to understand the unfolding story of this disease in each patient so they can get the best care.”
All of the people who logged their symptoms experienced loss of smell and headaches, but then had a varying combination of lesser-known side-effects as the illness set in — including confusion, abdominal pain and shortness of breath.
The six clusters were broken down by order of severity as follows:
- Flu-like with no fever: Headache, loss of smell, muscle pains, cough, sore throat, chest pain, no fever.
- Flu-like with fever: Headache, loss of smell, cough, sore throat, hoarseness, fever, loss of appetite.
- Gastrointestinal: Headache, loss of smell, loss of appetite, diarrhea, sore throat, chest pain, no cough.
- Severe level one, fatigue: Headache, loss of smell, cough, fever, hoarseness, chest pain, fatigue.
- Severe level two, confusion: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain.
- Severe level three, abdominal and respiratory: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain, shortness of breath, diarrhea, abdominal pain.
The first three clusters were more common in younger and healthier patients, while the last three more “severe” symptoms were more likely in older patients or those with preexisting conditions, such as diabetes, lung disease and obesity.
Only 1.5% of people with cluster 1, 4.4% of people with cluster 2, and 3.3% of people with cluster 3 required breathing support, such as extra oxygen or ventilators, the researchers found.
But the likelihood of needing breathing support rose in the latter three clusters, with 8.6%, 9.9% and 19.8% respectively.
Nearly half of the patients in cluster 6 ended up in the hospital, compared with just 16% of those in cluster 1. Most COVID-19 patients who need breathing come to the hospital around the 13th day after their first symptoms, the scientists said.
But being able to identify which cluster a patient falls in by the fifth day of symptoms would give doctors an early warning about whether the person will need intensive care.
“These findings have important implications for care and monitoring of people who are most vulnerable to severe COVID-19,” said Dr. Claire Steves from King’s College London.
“If you can predict who these people are at day five, you have time to give them support and early interventions such as monitoring blood oxygen and sugar levels, and ensuring they are properly hydrated — simple care that could be given at home, preventing hospitalizations and saving lives.”
The first group made up the largest share of participants, with 462 patients, while there were 315 patients in the second group, 216 in the third, 280 in the fourth, 213 in the fifth and 167 in the sixth.
The study has not been peer-reviewed.