Considering the results of all these pairs of metabolite ratios should help to diagnose all patients with 5ARD.
Although the diagnosis of 5ARD by USP appears straightforward, caution must be exercised when interpreting results for neonates and young infants, since metabolites of cortisol are almost exclusively derived from the 11-oxo metabolite cortisone at this early-stage of life (35).
Instead, mutational analysis of SRD5A2 is the key to the diagnosis of 5ARD.
Nevertheless, for those with both tests performed, the concordance rate is 100%, providing strong evidence that USP is an ideal test for biochemical phenotyping in 5ARD after 3 months of age with the rationale stated above.
In conclusion, 5ARD can be confidently diagnosed by USP from 3 months postnatally and by mutational analysis of SRD5A2.
11] Nonstandard abbreviations: T, testosterone; DHT, dihydrotestosterone; 5ARD, 5[alpha]-reductase 2 deficiency; hCG, human chorionic gonadotropin; USP, urinary steroid profiling; DSD, disorders of sex development; THF, tetrahydrocortisol; Ad, androsterone; Ae, aetiocholanolone; 11-OH Ad, 11-hydroxyandrosterone; THB, tetrahydrocorticosterone.