9068
Plasma was tested before and after ( 14 + / - 7 . 5 [ SD ] days ) surgery for IgG antibodies to the complex of heparin / platelet factor 4 , using a standardized , validated enzyme - linked immunosorbent assay ( ELISA ) .
 IgG antibodies, heparin / platelet factor 4
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 IgG antibodies, heparin / platelet factor 4