The second category of errors was due to the reporting of aspiration pneumonia on the death certificate. In cases where the string "aspiration" and pneumonia" were not reported in the same text field MetaMap processed the string separately thus yielding two codes: one for aspiration and the other pneumonia, instead of one code for "aspiration pneumonia" [C0032290]. In an initial review of MetaMap we found MetaMap had difficulties processing the phrase "pneumonia secondary to acute aspiration", therefore, our rule detection algorithm excluded cases where the code for pneumonia and aspiration were present in the same text field.