Bicarbonate, Plasma

Diagnostic Use

Bicarbonate is an anion that has an important role in acid-base balance.

Plasma bicarbonate may be requested to give an approximate indication of acid-base status however a venous/arterial blood gas should be taken to fully evaluate the acid-base profile.

Department

Core Biochemistry

Delphic Registration Code

HCO3

Synonyms

Carbon dioxide
HCO3
TCO2

Turnaround Time

2 hours

Test Code

4253

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin - Non-gel (Green Cap)

Preferred if West Coast

• Lithium Heparin - Gel (Light Green Cap)

Acceptable

• Serum (Red Cap)
• SST II (Gold Cap)
• Lithium Heparin - Gel (Light Green Cap)

Preferred Sample Volume (ml)

4.5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Lithium Heparin - Non-gel (Green Cap)

Preferred Sample Volume (ml)

0.6

Additional Specimen Information

- All samples must be collected and delivered to the laboratory anaerobically (i.e. no exposure to air and tightly capped)
- Unseparated lithium heparin PST or whole blood samples must be unopened and delivered to the laboratory within 30 min of collection.
- Samples for delivery to the laboratory >30 min after collection should be collected into SST or PST gel tubes and centrifuged to separate within 30 min. These samples should then be delivered to the laboratory, unopened, within 2 hours of collection.

Paediatric Specimen 600 µL heparin microtainer

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

0.2

Transport to Lab

Chilled (2 - 8 degrees Celsius)

Interpretation

In the absence of a blood gas profile, the plasma bicarbonate can only give an approximation of the acid-base status.

A low plasma bicarbonate may suggest the presence of a metabolic acidosis or (more rarely) metabolic compensation for a chronic respiratory alkalosis.  Another common cause of a low bicarbonate is an old specimen which has been uncapped, due to loss of bicarbonate from the specimen (as CO₂) to the ambient atmosphere.

A high plasma bicarbonate may be due to a metabolic alkalosis or metabolic compensation for a chronic respiratory acidosis.

Bicarbonate may be falsely elevated in specimens with an LDH >2,000U/L. If the patient has (or is likely to have) an LDH >2,000U/L, bicarbonate should be measured on a blood gas specimen.

Bicarbonate is part of the anion gap calculation.

Reference Intervals

Test Method

Enzymatic spectrophotometry, on a Beckman Coulter AU5822 analyser.

Non-Funded Test Cost

$5.53 (Exclusive of GST)

Billing Code

4523

Contact Information

Enquiry Form