Indicates the E-Commerce index.

It is populated by the 3DS authentication server (ACS) when the buyer has correctly authenticated him/herself (vads_threeds_status equals "Y" or "A").
  status = Y status = A status = U status = N
VISA and AMEX 5 6 7 -
MasterCard 02 01 - -

Output field, returned in the response (IPN and Return URL).

Format n..2
Category Authentication of cardholder.