Reply To: Blood types Home › Forums › English Braille American Edition › Blood types › Reply To: Blood types November 18, 2010 at 11:45 am #20580 Chris ClemensKeymaster Hello there,To answer your initial question, yes, you would need letter indicators for AB negative as well as for A positive. Remember, in literary braille, you do not use the mathematical symbols; You would replace the symbols with the words. Jana