. ▁It ▁is ▁based ▁on ▁positive ▁selection ▁using ▁Ep C AM - specific ▁ant ib od ies . ▁M aint rac ▁uses ▁an ▁approach ▁based ▁on ▁micro scop ic ▁identification ▁of ▁circul ating ▁tum or ▁cells . ▁To ▁prevent ▁damage ▁and ▁loss ▁of ▁the ▁cells ▁during ▁the ▁process , ▁M aint rac ▁uses ▁just ▁two ▁steps ▁towards ▁the ▁identification . ▁In ▁contrast ▁to ▁many ▁other ▁methods , ▁main t rac ▁does ▁not ▁pur ify ▁the ▁cells ▁or ▁en rich ▁them , ▁but ▁ident ifies ▁them ▁within ▁the ▁context ▁of ▁the ▁other ▁blood ▁comp ounds . ▁To ▁obtain ▁vital ▁cells ▁and ▁to ▁reduce ▁stress ▁of ▁those ▁cells , ▁blood ▁cells ▁are ▁prepared ▁by ▁only ▁one ▁cent rif ug ation ▁step ▁and ▁er yth ro cy te ▁l ysis . ▁Like ▁Cell Search , ▁main t rac ▁uses ▁an ▁Ep C AM ▁ant ib ody . ▁It ▁is , ▁however , ▁not ▁used ▁for ▁en rich ment ▁but ▁rather ▁as ▁a ▁flu ores cent ▁marker ▁to ▁identify ▁those ▁cells . ▁T ogether ▁with ▁the ▁nuclear ▁st aining ▁with ▁prop id ium ▁i od ide ▁the ▁main t rac ▁method ▁can ▁distinguish ▁between ▁dead ▁and ▁living ▁cells . ▁Only ▁vital , ▁prop id ium ▁ex cluding ▁Ep C AM ▁positive ▁cells ▁are ▁counted ▁as ▁potential ▁tum or ▁cells . ▁Only ▁living ▁cells ▁can ▁grow ▁into ▁tum ors , ▁therefore ▁dying ▁Ep C AM ▁positive ▁cells ▁can ▁do ▁no ▁harm . ▁The ▁susp ension ▁is ▁anal ys ed ▁by ▁flu ores c ence ▁micro sc opy ,