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Interexaminer reliability of transrectal ultrasound for estimating prostate volume
S Sech1, J Montoya, C J Girman
1Department of Urology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA.
Purpose:
We investigated the interexaminer reliability of transrectal ultrasound measurement of total prostate and transition zone volume among 3 examiners with various levels of experience.
Materials And Methods:
A total of 121 patients 39 to 82 years old (average plus or minus standard deviation 60.7 +/- 10.3) from a single urology clinic volunteered to participate. Patients with prostate cancer, previous prostate surgery or recent invasive prostatic examination were excluded from study. Each individual was examined independently by each of 3 examiners with various levels of experience, including an attending urologist, a PGY-2 resident in the second year of general surgery before urology training and a PGY-4 resident in the second year of urology training. Transrectal ultrasound was performed in each case by each examiner in pre-specified random order.
Results:
Mean total prostate and transition zone volume was 35.9 +/- 27.2 and 15.6 +/- 18.8 ml., respectively. Interexaminer agreement or reliability of the ultrasound measurements was high for total prostate and transition zone volume (intraclass correlation 0.96, 95% confidence interval [CI] 0.95 to 0.97 and 0.93, 95% CI 0.90 to 0.95, respectively). For individual prostatic dimensions reliability estimates were 0.78 to 0.86, while for transition zone dimensions reliability was 0.85 to 0.90. Total prostate volume reliability was higher for prostate volume greater than 40 ml. versus smaller prostates (intraclass correlation 0.95, 95% CI 0.90 to 0.97 versus 0.77, 95% CI 0.67 to 0.84). Mean differences in transrectal ultrasound measurements by different examiners were highest for the resident with least experience.
Conclusions:
The reliability of transrectal ultrasound measured total prostate and transition zone volume is high for examiners with different levels of experience at this institution. Reliability in patients without prostate cancer appears to be better for larger volume prostates and for examiners with more experience.