Anion gap - plasma or serum
Last updated: Wednesday, 07, April, 2004
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|Specimen||5 mL blood in lithium heparin or plain tube.|
Calculated parameter: Anion gap = (Na + K) - (Cl + HCO3).
Some laboratories do not include K in the equation.
| Reference Interval|
8-16 mmol/L (4-13 mmol/L if K not included).
Investigation of aetiology of metabolic acidosis.
An increased anion gap is seen in metabolic acidosis due to unmeasured anions that accumulate in renal failure; ketoacidosis; lactic acidosis; drug (eg, salicylate), ethylene, glycol and methanol toxicity; and in any situation where increased accumulation of acidic anions occurs.
Metabolic acidosis with a normal anion gap is seen in renal tubular acidosis and in other causes of bicarbonate loss eg, diarrhoea.
Sirker AA et al. Anaesthesia 2002; 57(4): 348-356.