Establishment of Novel Non-stretched Penile Length (Flaccid) Cut-off Point and Normative Data in Iranian Prepubertal Children and its Significance: Observational Analytical Study

Background: The penile aged-matched value should be determined to define abnormal penile length. Objectives: The purpose of this study was to establish novel reference values and flaccid penis length cut-off points for prepubertal children aged 6 - 15 years. Methods: In this study, 300 micropenis children were studied. In order to assess the diagnostic test power, 300 healthy boys were also evaluated as a control group. All children were divided into ten age groups (60 boys in each group). In order to obtain a non-stretched penile length (NSPL) cut-off point, stretched penile length (SPL) and NSPL mean values were separately calculated for each age group. We subtracted these two values to get the mean difference, which was subtracted from the standard SPL cut-off point to obtain the NSPL cut-off point for each age group. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were defined to assess diagnostic test power. Results: NSPL cut-off point for the age groups of 6 - 7, 7 - 8, 8 - 9, 9 - 10, 10 - 11, 11 - 12, 12 - 13, 13 - 14, 14 - 15, and 15 - 16 years was 2.8, 2.9, 2.9, 3.8, 3.9, 4.4, 4.2, 4.8, 6.6, and 8.1 cm, respectively. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of NSPL were 100% (95% CI, 98.53 - 100.00), 94.66% (95% CI, 89.77 - 96.28), 7.25% (95% CI, 4.64 - 11.16), 100%, and 97.33% (95% CI, 91.09 - 99.59), respectively. The AUC was 0.82, showing that the diagnostic power of the test was good. Conclusions: This study aimed to attain precise reference values of flaccid penis measurement for children. It seemed that the flaccid method is less observer-dependent, more tolerable, and repeatable. It should be mentioned that this new method does not replace the standard SPL method, while utilizing two reference values together can help to detect the size of the penis more accurately, especially in children. The new cut-off point can be used by all primary care practitioners and pediatric nurses as a reference for prepubertal boys to prevent misdiagnosis or overdiagnosis of micropenis.