Dr. Alvan Feinstein, widely regarded as the founder of clinical epidemiology and patient-oriented medicine, died Oct. 25 while attending an awards ceremony in Toronto. He was 75.

The cause was a heart attack, said Dr. Ralph I. Horwitz, a colleague of Dr. Feinstein and chairman of the department of medicine at Yale.

Feinstein had worked at the Yale School of Medicine since 1974, and was the Sterling Professor of Medicine and Epidemiology, the medical school’s most prestigious professorship.

He is widely known among epidemiologists as a pioneer, and has contributed significantly to virtually all facets of clinical research. One of his greatest innovations was his application of mathematics to the field of medicine, creating what he called “clinimetrics.” This allows doctors to remain consistent in evaluating a patient’s qualitative conditions, such as pain, distress, and disability, through the use of clinical indexes and rating scales.

“He was one of the most original characters of American medicine. He created and developed patient-based data, and influenced the lives of countless people,” said Horwitz.

Feinstein was not afraid to challenge widely held beliefs, and used novel methods of clinical investigation to improve techniques of diagnosis and prognosis, his colleagues said. In particular, his studies on rheumatic fever have led to a significant decline in instances of the disease.

In the late ’50s, by studying a large population of patients with rheumatic fever, he discovered that early diagnosis of the disease did not always keep patients from developing heart ailments later on in life, because the only form of the disease that can be diagnosed early seldom leads to heart disease.

Feinstein later applied similar techniques to cancer research. Last year, he headed a team that showed that breast cancers do not always grow at the same rate, and that not all cancers detected early by mammograms necessitate aggressive treatment.

“He was a seminal thinker. He possessed an intellect, a sense of inquiry that was unparalleled. He was an extraordinary clinical scientist,” said Mary Charlson, Professor of Medicine at Cornell University.

Feinstein was born in Philadelphia and received both his undergraduate degree in mathematics and his medical degree at the University of Chicago. Before arriving at Yale, he was Medical Director of Irvington House, an affiliate of New York University just outside New York City.

Feinstein published over 400 clinical studies and six books. Two of his books, “Clinical Judgment” (1967) and “Clinical Epidemiology” (1985) are among the most widely referenced books in clinical epidemiology, according to the New York Times.

He is survived by his wife, Lilli Sentz of New Haven; and two children, Daniel, of Camden, Maine., and Miriam F. Gottlieb of Ellenville, N.Y.