| 436 / | HD | CHEMISTRY: ANALYTICAL AND IMMUNOLOGICAL TESTING | 
| 536 | DF | INVOLVING IMMUNE COMPLEX FORMED IN LIQUID PHASE {2} | 
| 538 | DF | .~ Separation of immune complex from unbound antigen or antibody {3} | 
| 539 | DF | .~.~ Involving precipitating reagent {1} | 
| 540 |  | .~.~.~ Double or second antibody |