Inter/intra investigator variation in orchidometric measurements of testicular volume by ten investigators from five institutions

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To perform quality control studies on testicular volume measurements for a multi-center epidemiological study of male reproductive function.


We constructed a data matrix with a balanced assignment for 2 consecutive days by ten investigators (andrological career: 4-21 years) from five institutions and 12 male volunteers aged 20–26 years. Testicular volume was measured by Prader's orchidometer. A skilled technician also performed an ultrasound estimate of testicular volume.


A statistically significant inter-investigator variation was found for both testes (P <0.05). In addition, there was a statistically significant investigator-by-volunteer interaction in testicular volume measurement (P <0.01). However, there was no statistically significant difference in the two measurements performed on consecutive days for either testis. The testicular volumes for both the right and left testes as estimated by ultrasonography were smaller than results using the orchidometer. However, there was no statistical significance (P >0.05). The difference in experiences of the investigators did not significantly correlate with accuracy of measurements in either testis.


The present study revealed significant differences in the results of estimation of testicular volume among the ten investigators, but intra-investigator variation was not considerable. Improved training and proper standardization of the measurement will be necessary before starting a multi-center study based on an andrological examination.

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