Inter-rater reliability of a modified Karnofsky scale of performance status for HIV-infected individuals

The Karnofsky Scale of Performance Status (KPS) is a measure of health stat us that is widely used for HIV-infected persons, although few studies have documented its reliability and validity for HIV. We developed a modified KP S in an attempt to make it more appropriate for use in HIV-infected persons and evaluated its inter-rater reliability in a multicenter study. Patients (N = 657) were recruited from five hospitals in three Italian cities; resp onses were scored using the modified scale by three different raters in eac h hospital: one experienced physician, one young physician, and one nurse. Kendall's correlation test showed a strong inter-rater agreement for the to tal of observations: 0.82 between the two physicians, 0.77 between the expe rienced physician and the nurse, and 0.76 between the young physician and t he nurse. The analysis of variance showed a strong effect of the stage of t he disease on the KPS score. The specific hospital had little effect, where as the effect of the type of rater disappeared when the nurse was excluded from the analysis. This modified scale demonstrated a good reliability, alt hough training of raters could help to eliminate differences among raters a nd among hospitals.