NY -- Standard&Poor's CreditWire 10/20/98 –- Standard&Poor's today assigned its double-'A' rating to North Carolina Medical Care Commission's $115 million revenue bonds series 1998, issued for Mission St. Joseph's Health System, N.C. The bonds are expected to sell Nov. 11, 1998. The rating on the health system's revenue bonds reflects its: -- Role as the dominant health system in Western North Carolina, a region encompassing the 14 westernmost counties of the state; -- Historically strong financial performance and liquidity; and -- Good management and strategic planning. Currently, the parent corporation -- Mission St. Joseph's Health System -- is the obligated group's only member, but it controls the hospitals and other designated members and holds substantially all