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Total Protein (blood)

Determination of total protein is a quantitative measurement of the concentration of all proteins present in plasma (paediatrics) or in serum (adults; note that this excludes clotting factors). The major proteins are albumin and the immunoglobulins (principally IgG, IgA and IgM). Many other proteins are included in the measurement but individually none contributes more than 5% of the total, and most much less.

General information

Collection container:

Adults - serum (with gel separator, 4.9mL Sarstedt brown top)

Paediatrics - lithium heparin plasma (1.2mL Sarstedt orange top tube)

Type and volume of sample: The tubes should be thoroughly mixed before transport to the lab. The test may be added to a profile without provision of a separate specimen provided a full tube has been received. This test is NOT included in the standard liver function profile.

Special precautions: Plasma protein concentrations increase with excessive stasis during venepuncture; blood should therefore be collected with a minimum of stasis.

Laboratory information

Method principle: Colorimetric assay

Divalent copper reacts in alkaline solution with protein peptide bonds toform the characteristic purple-colored biuret complex.

Protein + Cu2 (alkaline pH) → Cu-protein complex

The color intensity is directly proportional to the protein concentration. It is determined by measuring the increase in absorbance at 552 nm.

Biological reference ranges:

Up to 1 month 45-70 g/L
1 month to 1 year 55-72 g/L
>1 year 60-80 g/L
Total protein can be measured in other fluids. These reference ranges will NOT apply.


Turnaround time:

Urgent: 2 hours

Routine: same day

Clinical information

Clinical decision points: Total protein can be used to give an indication of total immunoglobulin concentration since ([total protein] - [albumin]) = [globulins] of which the major component is immunoglobulins.

Factors known to significantly affect the results: Total protein concentration is affected by hydration status of the patient.Levels can be up to 10% lower in recumbent patients compared to ambulatory patients.

 

(Last updated 25th June 2017)