Irvine-based Core Inc., a provider of health care and disability management services, recorded a second-quarter net loss of $4.5 million, or 61 cents a share, which included one-time charges of $4.9 million related to the acquisitions of Cost Review Services and Social Security Disability Consultants. Core posted net income of $683,330, or 9 cents a share, for the 1997 second quarter. Revenue increased 20% to $10.8 million from $9 million. For the first half, the company said it lost $4.3 million, or 59 cents, a share, contrasted with net income of $823,401, or 11 cents a share, a year ago. Revenue was up 22% to $20.9 million from $17.1 million.