Blood type is not linked to COVID-19 severity, but it may affect the likelihood of testing positive for the virus, according to a new study.

Investigators gathered data from more than 1,280 adults who tested positive for COVID-19 in five Boston-area hospitals from March 6 to April 16. They looked for an association between blood type and the need for hospitalization, intubation and risk of death due to the coronavirus.

While blood type did not prove to be tied to these adverse outcomes, the researchers did find that it was linked to diagnostic test results, reported senior author Anahita Dua, MBChB, from Massachusetts General Hospital, Boston.

Patients with types B or AB blood were more likely to test positive for COVID-19, whereas those with type O were less likely to test positive. In addition, patients who were Rh positive — a common characteristic of blood type — also had a relatively high chance of receiving positive COVID-19 results.

Based on these findings and other research to date, blood type should not be used to predict COVID-19 outcomes, recommended Dua. But the diagnostic test association is intriguing, she and her co-authors concluded.

“The Rh+ association with disease positivity appears to be a novel finding and warrants further investigation,” they wrote.

The study was published in Annals of Hematology