U se of a Passive Hemagglutination Inhibition Test for Monitoring L evels of Serum Carcinoembryonic Antigen Follow ing Surgical Therapy

A te c h n iq u e o f passive h em ag g lu tina tion in h ib itio n (P H I) has b e e n u sed to m on ito r lev e ls o f carc ino em bryon ic a n tig en (CEA) in h u m an sera follow ­ in g surg ical th e rap y . C E A w as co u p led to h u m an ty p e O -negative e ry th ro ­ cytes in th e p re sen ce o f b is-d iazo tized b e n z id in e . P re-op era tive an d post­ o p e ra tiv e se ra from 11 p a tien ts w ith p rim ary ad en o carc in o m as o f th e gastrointestinal tract and from one pa tien t w ith u lcerative colitis w ere then te s te d for th e ir capacity to in h ib it th e agg lu tin a tio n o f th e sen s itized cells in th e p re sen ce o f a p re d e te rm in e d am ount o f goat an ti-C E A serum . P ositive sera w ere d e f in ed as th ose w h ich in h ib ite d agg lu tin a tio n a t d ilu tio n s o f > 1:8. T h e p re -o p e ra tiv e sera from 11 o f th e 12 p a tien ts in h ib ite d agg lu tin a tio n at d ilu tio n s o f 1:16 o r greater. T h e on e n eg a tiv e se ru m w as from a p a tien t w ith p rim ary ad en ocarc in om a o f th e co lon in th e stage o f D u k es’ C. At one m on th post-resec tion , th e P H I ti te r o f six p a tien ts w ith co lon can ce r an d of th e p a tie n t w ith u lce ra tive colitis w as =£ 1:8. H o w ev er, b y four m onths po st-resec tion , a ll b u t th re e o f th e p a tien ts h ad P H I tite rs in th e positive range. T h e se e le v a te d tite rs w e re acco m p an ied b y recu rren ce o f tum or grow th and /o r m etasta tic d issem ination . A rad io im m uno assay was u se d to q u an tita te C E A in 22 o f th e sera w h ich h a d b e e n te s te d b y P H I. W h en positive sera w ere d e f in ed as th o se w h ich in h ib ite d a g g lu tin a tio n at d ilu tio ns o f > 1:8 a n d c o n ta in ed C E A in excess of 5 ng p e r m l, th e resu lts o f th e tw o p ro ced u res w ere in ag reem en t for 17 o f th e 22 spec im ens. F iv e sera, rep re sen ta tiv e o f tw o p a tien ts w ith colon cancer, w ere false n eg ative b y P H I.