Can Karnofsky performance status be transformed to the Eastern Cooperative Oncology Group scoring scale and vice versa?

There is no consensus regarding the equivalence of performance status between the Karnofsky (KPS) and the Eastern Cooperative Oncology Group (ECOG) scales. In the present study KPS and ECOG scores were compared in 150 consecutive cancer patients. An empirical relation was established through regression analysis in a subsample of 75 patients and the results tested in the second subsample. Transformation tables including 95 and 66% confidence intervals were calculated. Both performance scales are highly correlated, but inferences about individual patients were subject to a high level of error. These results stress the difficulty of translating one score to another, especially in the range of lower performance status where a wide spread is observed.