The International Prognostic Index (IPI) is a clinical tool developed by oncologists to aid in predicting the prognosis of patients with aggressive non-Hodgkin's lymphoma. Previous to IPI's development, the primary consideration in assessing prognosis was the Ann Arbor stage alone, but this was increasingly found to be an inadequate means of predicting survival outcomes, and so other factors were studied.[citation needed]
In 1984, the first prognostic indicator for advanced non-Hodkin's lymphoma was developed. An information theory guided, computer search and evaluation procedure entropy minimax was employed to discover the largest sub-groupings for which survival is as extreme as possible[1] In the clinical trials analyzed retrospectively and containing a large fraction of patients not matching the 'good' - of 'good' (Karnofsky status >80 and 'A" Symptoms and SGOT <36 U/L), 'poor' (Karnofsky status <70 or Night sweats) and 'intermediate' (All Remaining) prognosis patterns identified, a significant difference was found between the survival of patients with and those without a complete response to therapy. The authors concluded that trials using a patient mix weighted toward good prognosis will not find such a difference.
In 1993, a retrospective analysis was performed on 2031 patients with aggressive non-Hodgkin's lymphoma, of all ages, treated with a doxorubicin-based chemotherapy regimen such as CHOP between 1982 and 1987.[2] Several patient characteristics were analyzed to determine whether they were associated with differences in survival, and the factors that emerged as significant were, in addition to the Ann Arbor stage: age, elevated serum lactate dehydrogenase (LDH), performance status, and number of extranodal sites of disease.