Check if string contains a character followed by digits

I have the following string that start with specific letters only, A, B, C, D, followed by digits. The example of string is always the following:

"<A12 id='something>444</A12>"

or

"<B991 id='somethingsomething'>12311</B991>"

Can anyone help me to correctly check if the string contains one of those letters followed by digits in a string?