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Test ID: Bicarbonate
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Bicarbonate
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Useful For
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Diagnosis and treatment of acid-base imbalance in respiratory and metabolic systems.
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Method name and description
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Bicarbonate reacts with phosphoenolpyruvate (PEP) in the presence of PEPC to produce oxaloacetate and phosphate:
PEPC
PEP + HCO3  - oxaloacetate + H2PO4-
The above reaction is coupled with one involving the transfer of a hydrogen ion from NADH analog to oxaloacetate using MDH.
MDH
Oxaloacetate + NADH analog + H+ malate + NAD+ analog
The resultant consumption of NADH analog causes a decrease in absorbance, which is proportional to the concentration of bicarbonate in the sample being assayed.
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Clinical information
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Bicarbonate is the second largest fraction of the anions in plasma. Included in this fraction are the bicarbonate (HCO3 -) and carbonate (CO3 2-) ions, as well as the carbamino compounds
The bicarbonate content of serum or plasma is a significant indicator of electrolyte dispersion and anion deficit. Together with pH determination, bicarbonate measurements are used in the diagnosis and treatment of numerous potentially serious disorders associated with acid‑base imbalance in the respiratory and metabolic systems.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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The preferred specimen is from venous blood collected anaerobically in the usual manner for bicarbonate analysis. Bicarbonate content in uncapped tubes decreases approximately 4 mmol/L after one hour.
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Storage and transport instructions
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Storage: 7 days at 4°C
40 hours at 2 – 8°C
6 months at ‑20 °C or -80°C
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed, icteric and lipemic, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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Factors affecting test performance and result interpretation
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The fluctuating ambient CO2 concentration may interfere with the CO2‑L assay leading to higher CO2 results.
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
STAT: 1 hour
Routine: One working day
Specimen retention: 4 days
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