Ammonia preanalytics, patient groups and laboratory method
| Condition | Patients | Method | Effect on mean plasma ammonia (µmol/L) | Reference |
| Power grip variable intensity for 15 mins | Hospital | Seligson diffusion | No effect in controls until high intensity (96 µmol/L), effect on cirrhotics increased across all levels, 30µmol/L to 87 µmol/L | 91 |
| Sweat | Healthy | Seligson diffusion | 10–50 times blood ammonia-sweat ammonia increasing with decreasing sweat pH | 92 |
| Smoking tobacco | Hospital | Ion-exchange/phenol | After 1 hour an increase of 10 µmol/L | 93 |
| Capillary versus venous sample | Hospital | Roche 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 sample | Hospital | Roche 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 min | Healthy | Enzymatic method | Mean 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 transferase | Healthy | Enzymatic method | Positive correlation | 95 |
| Tourniquet and clench | Hospital | Technicon RA-XT (Bayer Diagnostics, Basingstoke, UK) GLDH (Sigma diagnostics, Poole UK). | Increase of 60–75 µmol/L | 96 |
| Effect of hepatic dysfunction | Hospital | An 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-off | Unclear | Roche Integra 800 | Haemolysis did not add anything over delay in time to separation Haemolysis Index at least 200 at ammonia 28 µmol/L | 98 |
| Temperature including ice, chill centrifuge versus room temperature | Healthy | AU2700 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 | 99 |
| Smoking cannabis | Hospital | Colorimetric assay kit (BioVision Inc., Milpitas, CA) | After 90 min an increase of 35 µmol/L was seen | 100 |
| EDTA versus Li-Hep versus oxalate | Healthy | Roche COBAS c501 GLDH | EDTA 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 | 89 |
| Protein of 30 g and 60 g intake after 2–3 hours | Healthy | PocketChem 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 |