Best indication for testicular biopsy in a male is

"The testis biopsy is a useful adjunct in the infertility evaluation because it provides direct information regarding the state of spermatogenesis.............. This procedure is most useful in the azoospermic patient, in which it is often difficult to distinguish between a failure of sperm production and obstruction within the reproductive tract ducts. A testis biopsy allows definitive delineation between these 2 conditions and can guide further treatment options in azoospermic men " - Smith's Urology