Abstract:

Objective To study the interference effects of endogenous substances [hemoglobin（Hb）,bilirubin（Bil） and chyle granules] on the measurement of plasma ammonia by enzymatic assay method [glutamic dehydrogenase（GLDH）method] and dry chemistry method. Methods According to the Clinical and Laboratory Standards Institute（CLSI） EP7-A2 guideline,clinical plasma samples were collected,and basic samples with high and low concentrations were prepared. GLDH method and dry chemistry method were used to measure plasma ammonia respectively,and the relative deviation（high value samples） and absolute deviation（low value samples） of plasma ammonia determination results between interference samples and basic samples were calculated. The allowable deviation standard of the Royal College of Pathologists of Australasia（RCPA）（±3 μmol/L for plasma ammonia ≤30 μmol/L,±10% for plasma ammonia >30 μmol/L） was used as the clinical acceptable standard. Results Different concentrations of Hb did not interfere with the high and low value samples of plasma ammonia determined by dry chemistry method,and all the deviations were within the allowable deviation range. Hb had negative interference on the high and low value samples of plasma ammonia determined by GLDH method,and the degree of interference increased with the increasing of Hb concentrations. Bil had positive interference on the low value samples of plasma ammonia determined by dry chemistry method,when Bil≥184.4 μmol/L,it had exceeded the allowable deviation range. There was no interference on the high value samples. Different concentrations of Bil had negative interference on the low value samples of plasma ammonia determined by GLDH method. For the high value samples of plasma ammonia,when Bil≥246.2 μmol/L,it had negative interference on GLDH method. Chyle had no interference on the high value samples of plasma ammonia determined by dry chemistry method. There was positive interference in the chyle concentration of 612 FTU,and there was negative interference in the chyle concentration of 1 534 FTU. Different concentrations of chyle had negative interference on the samples with low value samples of plasma ammonia determined by GLDH method. For the high value samples of plasma ammonia,except the chyle concentration of 306 FTU,the other chyle concentrations had negative interference. Conclusions The anti-interference ability of dry chemistry method to Hb,Bil and chyle is better than that of GLDH method,but these interfering substances will affect the repeatability of the 2 methods.

Key words: Plasma ammonia, Interference, Hemoglobin, Bilirubin, Chyle