Upsala J M e d Sci 91: 222, 1986 Evaluation of Blood Ammonia Checker According to Daiichis System , Maria Wettstam-Andersson University Hospital, Department of Clinical Chemistry, Uppsala, Sweden INTRODUCTION P r e s e n t a t i o n o f D a i i c h i s system f o r d e t e r m i n a t i o n o f b l o o d ammonia i n c a p i l l a r y whole b l o o d . A c c o r d i n g t o t h e manufacture, t h e system has a c l i n i c a l use i n s c r e e n i n g f o r hyperammoneniia and s t a t p r o c e d u r e f o r l i v e r coma. The system has been t e s t e d f o r l i n e a r i t y and i m p r e c i s i o n . PRINCIPALS Whole b l o o d , 20 v1 i s a p p l i e d t o a r e a g e n t p l a t e w h i c h c o n t a i n s an a l k a l i n e b u f f e r ( s o d i u m c a r b o n a t e , sodium b i c a r b o n a t e ) . The specimen becomes a1 k a l i n e and t h e ammonia i s l i b e r a t e d f r o m t h e b l o o d . The ammonia gas d i f f u s e s t h r o u g h a p o l y p r o p y l e n e f i l m a t t h e b o t t o m o f t h e r e a g e n t p l a t e , and p e n e t r a t e s i n t o a c o l o r d e v e l o p i n g s e c t i o n , w h i c h i s t r e a t e d w i t h a pH b u f f e r ( b r o m c r e s o l g r e e n ) . The degree o f c o l o r development i s p r o p o r t i o n a l t o t h e amount o f ammonia r e l e a s e d . The b l o o d ammonia c o n c e n t r a t i o n w i l l be d e t e r m i n e d r e f l e c t r o m e t r i - c a l l y b y i n s e r t i n g t h e t e s t p l a t e i n t o t h e " B l o o d ammonia c h e c k e r " . RESULTS A r e f e r e n c e v a l u e o f 71+21,8 u m o l / l (mean + SD) was o b t a i n e d b y a n a l y s e s The l i n e a r i t y o f t h e method was good i n t h e r a n g e 25-270 p m o l / l , o f c a p i l l a r y b l o o d f r o m 22-healthy i n d i v i d u a l ? . T a b l e 1. I m p r e c i s i o n o f t h e method a t d i f f e r e n t c o n c e n t r a t i o n l e v e l s . conc. l e v e l ( u m o l / l ) n x + SD cv % 9 29 +-11.6 40.0 5 7 7 T 6.4 8.3 10* 123 T 13.1 10.7 5** 268 '7 30.0 11.7 5** 323 11.4 3.5 * The i n c r e a s e i n NH ' was a c h i e v e d b y p l a c i n g a c u f f a r o u n d t h e b i c e p s m u s c l e i n f l a t e i t $0 a p r e s s u r e e x c e e d i n g t h e s y s t o l i c p r e s s u r e by 30 mmHg, and p e r f o r m i n g m u s c u l a r e x e r c i s e . Whole b l o o d supplemented w i t h ammoniumchloride. ** CONCLUSIONS The " B l o o d ammonia c h e c k e r " i s a s m a l l e a s y t o use system w h i c h c o u l d be u s e d i n bed s i d e t e s t i n g . T h e r e i s , however, a r a t h e r pronounced d i f f e r e n c e i n venous and c a p i l l a r y b l o o d ammonia c o n c e n t r a t i o n s . Due t o t h e h i g h i m p r e c i - s i o n i n t h e l o w c o n c e n t r a t i o n r a n g e t h e system i s n o t s u i t a b l e f o r venous b l o o d specimens. 222