Plasma
Urine
Fluid
Adult patient:
Heparin gel tube
Minimum blood volume: 5 mL
Plain bottle
Minimum volume: 10 mL
24 Hr urine:
U1 bottle
Plain bottle
Minimum volume: 10 mL
Paediatric patient:
Paediatric heparin tube
Number of vials: 1
Minimum blood volume: 1.3 mL
Authorisation code required
No
24 Hr available service
Yes
(Call extension: 3353 for express result)
No
No
Method
Ion selective electrode
Reference interval
Plasma: 102 - 114 mmol/L
(Source: from local population study in 1986)
24 Hr urine: 110 - 250 mmol/d
The urinary excretion of chloride varies significantly with dietary intake. The values given are typical of subjects on average diet.
Clinical indication
Plasma:
To assess the possible cause of acid-base disturbances, including calculation of the anion gap.
Urine:
To define the site of chloride loss in metabolic alkalosis and other electrolyte disturbances when it is not obvious clinically. Monitoring compliance with a low salt diet.
Result interpretation
Plasma:
Hyponatraemia and metabolic alkalosis are associated with hypochloraemia.
Hypernatraemia and metabolic acidosis, due to renal tubular acidosis or bicarbonate loss, are associated with hyperchloraemia.
An increased anion gap indicates accumulation of an anion other than chloride (e.g. lactate, hydroxybutyrate); this usually occurs with metabolic acidosis.
Urine:
The urine chloride concentration is usually similar to that of sodium in urine, since sodium and chloride are generally reabsorbed together.
An exception occurs when sodium is excreted with another anion, e.g. sodium bicarbonate in metabolic alkalosis, where the need to excrete excess bicarbonate may raise the urine sodium concentration despite the presence of volume depletion. In this setting the urine chloride concentration remains low and is frequently a better index of volume status.
Patients with a metabolic alkalosis and an associated urine chloride level of < 10 mmol/L are usually chloride deficient from gut or sweat loss and may require replacement therapy.
Measurement of uncertainty
Frequency of measurement
Daily