Researchers at Northwestern University have developed a laboratory test for measuring neutralizing antibodies against the coronavirus that requires only a single drop of blood, collected and dried on filter paper. “Blood samples can be self-collected at home, and sent to the lab in the mail‚” said Thomas McDade, whose team described the technique in a report posted on Tuesday on medRxiv ahead of peer review. Currently, to determine if someone has the neutralizing antibodies that protect against the virus that causes COVID-19, blood must be drawn at a clinic or doctor’s office and sent for analysis.