Measurement of pediatric testicular volume with Prader orchidometer: comparison of different hands

Measurement of testicular volume is a more readily available method of estimating spermatogenesis in adolescence. Traditionally, testicular volumes have been measured with different type of orchidometers or calipers. The most widely used orchidometer is the Prader orchidometer introduced in 1966. This type of orchidometer, a graded series of ellipsoid beads on a string, is used for testicular volume measurement, which is a useful index of puberty in male in order to evaluate male growth and development. Although it is more practical and inexpensive compared with ultrasonography, this instrument has been questioned in regard to its objectiveness in different hands. We designed a prospective clinical study to investigate the correlation between testicular size measurements of three different clinical investigators by using Prader orchidometer. A total of 100 testes in 50 boys with a mean age of 6.4 years (range 1–15 years) who presented to Urology and Pediatrics outpatient clinics of our hospital without urogenital complaints were enrolled to this study. The volumes of each testis were measured independently using Prader orchidometer by three different clinical investigators (A, B and C). Each investigator repeated testicular volume measurements blinded to measurements obtained by others. The measured volumes were recorded separately. Statistical analysis of the results was performed using Pearson’s correlation (r) to determine the correlation of orchidometer measurements between the examiners. All statistical analyses and power calculations were performed using computer software. Mean testicular volumes measured by three examiners A, B and C were 4.01±3.79 ml (SD) (2–18 ml), 3.66±3.46 ml (SD) (1–18 ml) and 3.86±3.54 ml (SD) (1–18 ml), respectively. The statistical correlation between the measurements of investigator A and B, A and C, and B and C showed a high correlation {r=0.954 (P<0.01), r=0.964 (P<0.01), and r=0.979 (P<0.01)}, respectively. In the present study, it was shown that testicular size measurement by using Prader orchidometer gives good correlation in different examiners’ hands and it is an objective and reliable method in pediatric urological practice.