Amid concerns among teams over the potential for false positives impacting players returning from COVID-19, the NBA on Wednesday updated its protocols to add an antibody test for players and staff who have recovered from the virus, according to a memo obtained by ESPN.

Because people who have recovered from COVID-19 can still have dead virus cells in their system be detected by tests, the league has now included the antibody test as part of its protocol for players and staff returning from the virus, according to the memo.

As the NBA prepares to resume play inside the league's bubble at the Walt Disney World Resort, teams have worried about the potential for prominent players to have false positive tests -- particularly during the postseason, sources told ESPN. On a recent call with the league's general managers, the question of what would happen if a false positive test takes place on a game day was raised to the league, sources said.

At least one player who contracted COVID-19, recovered and was subsequently cleared to travel to Orlando had registered several negative tests at Disney World and cleared quarantine upon arrival but later tested positive, sources said.

Several players who contracted the virus, including Denver Nuggets star Nikola Jokic and Sacramento Kings guard Buddy Hield, have returned to practice with their teams in Orlando. Others, like Houston Rockets star Russell Westbrook and Kings forward Harrison Barnes, are still at home recovering, with their return dates to be determined.

The memo laid out four steps each person has to clear to no longer be restricted from participating with their teams.

• At least 14 days must have passed from the latter of their first positive test or the resolution of their symptoms.

• They must pass two negative PCR tests at least 24 hours apart.

• They must return a positive antibody test within the past 30 days.

• They must pass a negative rapid coronavirus test before taking part in any close, physical contact with other people.

These steps were created after review by infectious disease experts and epidemiologists after consultation with both the NBA and the National Basketball Players Association.