Modified micro-scale enzymatic method for plasma ammonia in newborn and pediatric patients; comparison with a modified cation-exchange procedure.
We modified two "kit" procedures for plasma ammonia to make them suitable for use with newborn and pediatric patients. Available methods either require too large a specimen, are insufficiently sensitive in the normal range, or are too cumbersome. One was an enzymatic (Sigma Chemical Co., St. Louis, Mo. 63178), the other a cation-exchange (Hyland, Costa Mesa, Calif. 92626) method. The modified micro-scale enzymatic method requires 100 microliter of plasma (CV at 38 micronmol/liter, 8%). Reagent costs per patient assay, including controls and standards, are currently $0.53. An assay run can be completed in 30 min. The modified cation-exchange method requires 200 microliter of plasma; the within-run CV is 12% for a concentration of 34.2 micronmol/liter. Reagents currently cost $0.74 per assay and each run requires less than 2 h to complete. The correlation coefficient for the two methods was 0.98.
D000641:Ammonia / Q000097:blood*; D002648:Child; D002852:Chromatography, Ion Exchange / Q000379:methods; D003365:Costs and Cost Analysis; D005969:Glutamate Dehydrogenase; D006801:Humans; D007231:Infant, Newborn; D008832:Microchemistry; D011933:Reagent Kits, Diagnostic
D011933:Reagent Kits, Diagnostic; D000641:Ammonia; D005969:Glutamate Dehydrogenase