Electrolytes
Chloride
Chloride is the major negatively charged electrolyte in the fluid outside cells, and at the point of care it is measured by ion-selective electrode as part of electrolyte and blood gas panels. Results are usually available within a few minutes to support rapid assessment of acid-base and fluid status.
Why it is measured
Chloride helps characterise acid-base disturbances, including the anion gap and hyperchloraemic acidosis, and supports evaluation of fluid and electrolyte balance. It is interpreted alongside sodium, bicarbonate and the calculated anion gap rather than on its own.
| Typical range | Indicative adult range is approximately 98 to 107 mmol/L (equivalent to 98 to 107 mEq/L) in serum or plasma. Ranges vary by method and laboratory, and direct ion-selective electrode whole-blood values on POCT analysers can differ slightly from indirect serum measurements on central laboratory systems. |
|---|---|
| Sample | Whole blood (arterial, venous or capillary) on cartridge-based POCT blood gas and electrolyte analysers, or serum or plasma on benchtop POCT chemistry systems. Chloride is most commonly measured by ion-selective electrode. |
| Turnaround | Typically under 2 minutes on cartridge-based blood gas and electrolyte analysers. Around 12 to 14 minutes on benchtop disc-based chemistry systems. |
Point of care devices that report it
- Abbott i-STAT (CHEM8+ and EC8+ cartridges)
- Siemens Healthineers epoc Blood Analysis System
- Nova Biomedical Stat Profile Prime Plus
- Radiometer ABL90 FLEX
- Roche cobas b 221 / cobas b 123
- Abaxis Piccolo Xpress (electrolyte and metabolic panel discs)
Questions, answered
Why is chloride measured alongside sodium and bicarbonate?
Chloride, sodium and bicarbonate are interpreted together to assess acid-base and fluid balance. Chloride is also used to calculate the anion gap, which helps classify metabolic acidosis. Looking at chloride in isolation gives limited information, so POCT electrolyte panels typically report it with these other analytes.
Do point-of-care chloride results match the central laboratory exactly?
Values are usually comparable but not always identical. Most POCT analysers use direct ion-selective electrode on whole blood, while many central laboratories use indirect ion-selective electrode on serum or plasma, and these methods can give small systematic differences. Good practice is to follow trends on the same method where possible and to confirm unexpected results before acting on them.
What can cause an unexpected chloride reading at the point of care?
Pre-analytical and method factors can affect results, including contamination from intravenous fluids if a sample is drawn near an infusion line, prolonged sample storage, and interference from other halide ions such as bromide on some electrodes. Following the manufacturer instructions for sampling, running quality control and noting any flags helps support reliable results.