[Adaptation of Biomerieux enzymatic UV ammonia on Konelab analysers].
BACKGROUND
Circulating ammonia in normal patients is relatively low, despite the fact that ammonia is continually produced from endogenous amino acid metabolism. The physiopathological interest of plasmatic ammonia determination lies primarily in its relationships to hepatic insufficiency (cirrhotic or neoplasic), or the diagnosis and the forecast of the Reye's syndrome.


OBJECTIVE
This study describes an evaluation of plasmatic ammonia determination by the UV end point enzymatic method using GLDH on KONELAB(TM) analyzers.


METHODS
The glutamate dehydrogenase (GLDH : EC.1.4.1.3) catalyses the reducing amination of alpha-cetoglutarate in the presence of NH(4)(+) and of NADPH, H(+) to form glutamate and NADP(+). The reduction of NADPH,H(+)'s concentration, directly proportional to ammonia rates, is evaluated at 340 nm. All the conditions were met to optimize the method, while covering a satisfying field of measurement.


RESULTS
The evaluation of the modified method showed a good precision (repeatability: CV < 4 %; interserial reproducibility: CV from 2.01 to 2.93 %; Intraserial reproducibility: CV equal to 0.67%) and a very good accuracy. The field of measurement extends from 27 to 250 micromol/L, with a limit of detection (L(D)) lowered to 0.325 micromol/L.


CONCLUSIONS
The adapted technique is simple, fast, inexpensive and especially automatizable. It is in addition reliable and chiefly more sensitive, adapting particularly to the determination of plasmatic ammonia in urgency as in routine within our laboratory.
Mezzour
H
H
Laboratoire de biochimie-toxicologie, CHU de Monastir, Tunisie.
Neffati
F
F
Najjar
M F
MF
D000641:Ammonia / Q000097:blood*; D001322:Autoanalysis / Q000379:methods; D006801:Humans; D007202:Indicators and Reagents; D007700:Kinetics; D015203:Reproducibility of Results; D012202:Reye Syndrome / Q000097:blood / Q000175:diagnosis; D012680:Sensitivity and Specificity
D007202:Indicators and Reagents; D000641:Ammonia