Sensitivity analysis allows one to consider the effect of possible error in the assignment of values to uncertain parameters, and shows how varying these assigned values might change the eventual decision. The model assumes that renal pathology is the single significant untoward outcome of primary urinary tract infections. Wiswell and Geschke 8 found in a group of 35,929 uncircumcised male infants that non-circumcision was associated with death from invasive bacterial disease in two male infants with UTI in the first month of life. However, their data do not address the issue of causality, and neonatal UTI is generally thought to be acquired through hematogenous spread. A second assumption of the model is that a higher rate of urinary tract infection is the only significant untoward outcome of non-circumcision in the newborn period.
Penile cancer occurs almost exclusively in the uncircumcised male at a rate of eight per million.
Sensitivity analysis will be used to assess the effect of this assumption. The model does not directly address the issue of sexually transmitted diseases and circumcision due to the absence of prospective studies that control for confounding influences and to the conflicting evidence from retrospective data. While there are retrospective studies suggesting a higher risk of penile inflammatory conditions, such as balanitis, in uncircumcised males, a recent prospective study from New Zealand was unable to find a statistically significant higher risk of penile problems in uncircumcised boys in the first eight years of life. 13 Sensitivity analysis allows one to see the potential effect of ignoring these issues in the model. The model begins at a choice node or point of decision and goes through chance nodes where the uncertainties of events following the decision are represented.