Is it possible to pass variables from add_user_page?

The easiest and most clean way to solve that problem is using a specialised object.

First create a class that can hold extra information:

class Menu_Page
{
    public $extra="";

    public function render()
    {
        print $this->extra;
    }
}

Now create an object from that class …

$page        = new Menu_Page;
$page->extra="Hello World!";

… and register its method render() as callback:

add_users_page( 
    'Test', 
    'Test', 
    'manage_options', 
    'test', 
    array( $page, 'render' ) 
);