Please see this CRSP white paper (page 6) for more details.
"Pre-delist announcements are extremely rare for issues that were dropped by an exchange due to poor performance. However, the CRSP data contains a total of 412 issues that delisted due to liquidation, and 42.7 % of them have some type of pre-delist announcement of liquidation. The research staff found evidence of pre-delist announcements for 41.7% of the NYSE and AMEX liquidation issues and 44.1 % of the NASDAQ liquidation issues.
The dates of these announcements are located in the Date of Next Available Information (NEXTDT field) of the DELIST structure, but this field holds announcement dates only for issues that delisted due to liquidation. In the past, if liquidation proceedings were announced, then the NEXTDT was set equal to the Delisting Date (DLSTDT field). This policy no longer holds true for issues that delisted due to liquidation (i.e. issues with a 4** delist code.)"