Table 4

Ammonia preanalytics, patient groups and laboratory method

ConditionPatientsMethodEffect on mean plasma ammonia (µmol/L)Reference
Power grip variable intensity for 15 minsHospitalSeligson diffusionNo effect in controls until high intensity (96 µmol/L), effect on cirrhotics increased across all levels, 30µmol/L to 87 µmol/L 91
SweatHealthySeligson diffusion10–50 times blood ammonia-sweat ammonia increasing with decreasing sweat pH 92
Smoking tobaccoHospitalIon-exchange/phenolAfter 1 hour an increase of 10 µmol/L 93
Capillary versus venous sampleHospitalRoche Cobas Bio with Glutamate dehydrogenase(GLDH) Monotest (Boehringer Manheim)Increase in capillary of 74 µmol/L compared with venous plasma of 18 µmol/L 94
Platelet-rich versus platelet-poor sampleHospitalRoche Cobas Bio with GLDH Monotest (Boehringer Manheim)Platelet-rich plasma ammonia of 34 µmol/L versus platelet-poor plasma ammonia of 21 µmol/L 94
Temperature over 90 minHealthyEnzymatic methodMean rates of increase at 0°C, 20°C and 37°C were 3.9 µmol/L, 5.2 µmol/L and 25.2 µmol/L per hour, respectively 95
Platelet, erythrocyte, alanine transferase and gamma-glutamyl transferaseHealthyEnzymatic methodPositive correlation 95
Tourniquet and clenchHospitalTechnicon RA-XT (Bayer Diagnostics, Basingstoke, UK) GLDH (Sigma diagnostics, Poole UK).Increase of 60–75 µmol/L 96
Effect of hepatic dysfunctionHospitalAn enzymatic–Ultra violet kit from Thermo Electron Corporation
(Infinity) was used on our AU640 analyser (Olympus
UK Ltd, Hertfordshire) versus (Vitros 250, Ortho-Clinical
Diagnostics, UK).
Due to one step enzymatic may over estimated ammonia due to NADH consumption, leading to a positive interference which can be up to threefold difference and likely to influence clinical practice 97
Haemolysis and Haemolysis Index cut-offUnclearRoche Integra 800Haemolysis did not add anything over delay in time to separation
Haemolysis Index at least 200 at ammonia 28 µmol/L
Temperature including ice, chill centrifuge versus room temperatureHealthyAU2700 analyser (Beckman Coulter) using Randox Ammonia Reagent
GLDH enzymatic (Randox, Crumlin, Co,
Antrim, UK)
25.1 µmol/L versus 27.6 µmol/L for ice versus room temperature at 30 min, chilling centrifuge made no difference
If there was further delay of 30 min then difference of 11 µmol/L seen between ice, chill and room temperature
Smoking cannabisHospitalColorimetric assay kit (BioVision Inc., Milpitas, CA)After 90 min an increase of 35 µmol/L was seen 100
EDTA versus Li-Hep versus oxalateHealthyRoche COBAS c501 GLDHEDTA was more precise and stable once separated- 0.322
μmol/h at 4°C, 0.122 µmol/hour at −14°C, and negligible change at −70°C
Protein of 30 g and 60 g intake after 2–3 hoursHealthyPocketChem BA blood ammonia, microdiffusion (Lancashire, United Kingdom)Maximum mean increases of 54 µmol/L for 30 g at 2 hours and 71 µmol/L for 60 g at 3 hours 90