Objective. To show cluster analysis as a potentially useful tool in definin
g common outcomes empirically and in facilitating the assessment of prefere
nces for health states.
Data Sources. A survey of 224 patients with ventricular arrhythmias treated
at Kaiser Permanente of Northern California.
Study Design/Methods. Physical functioning was measured using the Duke Acti
vity Status Index (DASI), and mental status and vitality using the Medical
Outcomes Study Short Form-36 items (SF-36). A "k-means" clustering algorith
m was used to identify prototypical health states, in which patients in the
same cluster shared similar responses to items in the survey.
Principal Findings. The clustering algorithm yielded four prototypical heal
th states. Cluster 1 (21 percent of patients) was characterized by high sco
res on physical functioning, vitality, and mental health. Cluster 2 (33 per
cent of patients) had low physical function but high scores on vitality and
mental health. Cluster 3 (29 percent of patients) had low physical functio
n and low vitality but preserved mental health. Cluster 4 (17 percent of pa
tients) had low scores on all scales. These clusters served as the basis of
written descriptions of the health states.
Conclusions. Employing a clustering algorithm to analyze health status surv
ey data enables researchers to gain a data-driven, concise summary of the e
xperiences of patients.