USING REPEATED-MEASURES OF SYMPTOM SCORE, UROFLOWMETRY AND PROSTATE-SPECIFIC ANTIGEN IN THE CLINICAL MANAGEMENT OF PROSTATE DISEASE

Measurements of American Urological Association symptom score, peak ur ine flow rate and prostate specific antigen (PSA) are often followed o ver time in urological management. However, their interpretation is co nfounded by within-patient variability due to chance. Data from 2 clin ical trials are used to examine the magnitude of this variation. When these measures are repeated at a short interval variation is modest an d might easily be misinterpreted as a true change in patient condition . For example, approximately 20% of patients might be expected to have a chance increase or decrease in symptom score by at least 4.9 points , in peak urine flow rate by at least 4.1 ml. per second or in PSA by at least 1.6 ng./ml. Clinicians can use these data to help interpret r epeated measures of these variables in patients, and can consider obta ining paired measurements to decrease the effect of chance variation w hen they plan on following them over time.