the subsequent hearing before the GIP (Preliminary Investigation Judge) is the confirmation of charges hearing.
The first stage is when the police detain or arrest a suspect on charges and the Public Prosecutor then has 48 hrs while the suspect is detained or released on charges, to formulate charges before seeking confirmation of charges during the charges' confirmation hearing.
Hope this is clear! (awful lot
Alison

art. 390 cpp. Richiesta di convalida dell'arresto o del fermo - 1. Entro 48 ore dall'arresto o dal fermo il PM,..., richiede la convalida al giudice per le indagini preliminari... 2. il giudice fissa l'udienza di convalida al piu presto e comunque entro le 48 ore successive dandone avviso, senza ritardo, al PM e al difensore.

In federal courts of the United States, arraignment takes place in two stages. The first is called the initial arraignment and must take place within 48 hours of an individual's arrest, 72 hours if the individual was arrested on the weekend and not able to go before a judge until Monday.[1] During this arraignment the defendant is informed of the pending legal charges and is informed of his or her right to retain counsel. The presiding judge also decides at what amount, if any, to set bail. During the second arraignment, a post-indictment arraignment or PIA, the defendant is allowed to enter a plea.
Initial Appearance -- As soon as practicable after arrest, the alleged offender must be granted an Initial Appearance before a Magistrate Judge. The Magistrate Judge advises the accused of his or her rights and determines if he or she has the financial ability to hire an attorney or if a public defender must be appointed. The Magistrate Judge also sets release conditions, including any bond. At the same time, a federal prosecutor, known as an Assistant United States Attorney, may ask that the defendant be detained.