Does the Tort Immunity Act Give Immunity to a Doctor for Failing to Diagnose a Disease ?

In Michigan Avenue National Bank v. County of Cook, 191 Ill. 2d 493, 503-04, 732 N.E.2d 528, 535, 247 Ill. Dec. 473 (2000), plaintiff's decedent visited the defendant hospital numerous times complaining of a lump and sometimes pain in her left breast. The defendant doctors told her she had fibrocystic breast disease and did not perform any tests to determine whether it was cancer and did not treat her condition. Plaintiff argued, among other things, that defendant doctor should have taken steps that would have led to a diagnosis, and that the "misdiagnosis" of fibrocystic breast disease arrived at through the negligence of defendants constituted the proximate cause of the patient's death. Defendants argued that plaintiff was actually alleging a failure to diagnose and, therefore, defendants were immune under sections 6-105 and 6-106 of the Tort Immunity Act. 745 ILCS 10/6-105, 6-106 (West 1992). the trial court agreed and granted defendants' motion for summary judgment. The appellate court affirmed, and the supreme court allowed plaintiff's petition for leave to appeal. The supreme court held that where a plaintiff essentially alleges that a public entity fails to diagnose an illness, it is immune under section 6-106(a) of the Tort Immunity Act. Michigan Avenue, 191 Ill. 2d at 514. More-over, the supreme court stated that plaintiff's attempts to characterize its lawsuit as a case of I "misdiagnosis" does not remove its action for the ambit of subsection (a) of section 6-106. Michigan Avenue, 191 Ill. 2d at 514. The supreme court explained that the word "diagnosis" is not ambiguous and, thus, must be given its plain an ordinary meaning. Michigan Avenue, 191 Ill. 2d at 510. The court looked at several sources for the definition of a "diagnosis." Webster's dictionary defines "diagnosis" as the "art or act of identifying a disease from its signs and symptoms," and as an "investigation I or analysis of the cause or nature of a condition, situation, or problem." Webster's Third New International Dictionary 622 (1993). The Sloan-Dorland Annotated Medical-Legal Dictionary defines "diagnosis" as "the art of distinguishing one disease from another" and as the "determination of the nature of a case of disease." Sloan Dorland Annotated Medical-Legal Dictionary 199 (1987).