CINCINNATI-Jewish Health System agreed to join the Health Alliance of Greater Cincinnati by Jan. 1, 1996. Christ Hospital, with 550 beds, and 707-bed University of Cincinnati Hospital joined at the beginning of this year, and St. Luke Hospitals in northern Kentucky has agreed to join the alliance by July 1. Just one local hospital, Deaconess Hospital of Cincinnati, remains unattached to any of the area's four networks, a Health Alliance spokeswoman said. The alliance is studying areas for cooperation and cost savings, including closing hospitals. Jewish, with 540 beds, had 13,930 inpatient admissions, 161,498 outpatient registrations and 1994 revenues of $229 million. It has 2,300 employees and 1,392 physicians. The four alliance members had combined in-patient admissions of 74,000, outpatient registrations of 823,000 and revenues of $1 billion in its last fiscal year.