The measurement of erythrocyte ammonia using the Hyland Ammonia kit

We modified the Hyland Ammonia kit for plasma to measure blood ammonia from which the erythrocyte ammonia is calculated. Our modified method gave good recoveries and its precision based on replicate assays was excellent (CV less than 3.0%). The within-day and day-to-day precision was determined from pooled blood and aqueous ammonia solution respectively. The precision calculated from duplicate results was not as good but agreed with other published values. A critical examination of Hyland's method showed the efficiency of resin adsorption to be 78%, and that the resin caused a 16% reduction in the Berthelot reaction, while 4 mol/l NaCl increased the reaction by about 11%. Blood specimens for ammonia can be frozen but specimen instability occurred during the thawing process. Measurement of ammonia directly on frozen specimens overcomes this problem. The reference range for erythrocyte ammonia was 14.5-46.1 (mean 30.1, SD 7.9) mumol/l.