Serum Paraprotein

Paraprotein is an abnormal antibody (immunoglobulin) that is produced in excess by an abnormal monoclonal proliferation of plasma cells, typically in multiple myeloma. Other terms for such a protein are monoclonal protein, M protein, or myeloma protein

Sample type:

This is done on the serum of the patient.

Uses:

Elevated paraprotein level (above 30 g/l) in conjunction with end organ or biomarkers of malignancy, is diagnostic of multiple myeloma,

Precautions

1. Avoid prolonged application of a tourniquet. This will lead to hemoconcentration and give a false rise in values.

2. Avoid hemolysis and lipemic serum.

3. Avoid blood from the side of the I/V infusion which will lower the result.

Interference

Hemolysis: Additional discrete bands on α2/β regions

• Improper sample collection

• mechanical rupture or prolonged storage

• In vivo hemolysis may occur due to pre-eclampsia, hemolytic anemia, or sickle cell disease

• Additional bands may be misinterpreted as monoclonal proteins

Fibrinogen:

Fibrinogen migrates in the β/γ region

• Erroneous sample collection of plasma instead of serum

• IFE can rule out monoclonal protein from fibrinogen interference

• Treatment with thrombin or ethanol removes the fibrinogen peak

• Quantofix EDTA to identify EDTA samples

Contrast Dyes:

Contrast Dyes Interference in α2 region

• Contrast dyes absorb light at ~200 nm, which is the same wavelength used to quantify proteins in CE

• Contrast dyes have no effect on protein gel electrophoresis or immunofixation

Antibiotics Antibiotics : Interference in α or β region

• Antibiotics, such as piperacillin-tazobactam may produce an additional spike between α2 and β1 region

• Other antibiotics cause interference in CE: ceftriaxone, 5- flurocystosine (5-FC), and sulfamethoxazole

Pre analytical errors:

1. Sample preparation:

Some commonly made mistakes during sample preparation include:

• Employing an incorrect protein-to sample buffer ratio,

• Failure to remove insoluble material,

• Overloading and under loading of protein.

Corrective factor: sample should be determined using a standard protein assay

1. Miscalculating cross-linking factor of a polyacrylamide gel

Two factors control the pore size of a polyacrylamide gel, (a) the total concentration of acrylamide T and (b) the degree of cross-linking C:

T= (a+b) ×100V [%], C=b×100a+b [%]

a = mass of acrylamide in g

b = mass of methylenebisacrylamide in g

V = volume in mL

However, sometimes one mistakenly assumes that the given total concentration of acrylamide T is the percentage of acrylamide per volume and C (the cross-linking factor) is the percentage of methylenebisacrylamide per volume. This will lead to too much amounts of cross-linker in the gel. This will result in gels that are opaque, brittle and highly hydrophobic

Corrective action:

Prepare the solutions as per the equation noted above. Alternatively, it would be better to use commercially available acrylamide/methylenebisacrylamide stock solutions that are ready-to-use.

1. Temperature and time of polymerization for a polyacrylamide gel

Postanalytical phase:

1. Processing of results for transcription onto report forms

2. Reduce human error through root-cause analysis, process control, and education/communication.

Reference Ranges:

Normal Range: Adults (<75 years): Absent Adults (>75 years): Present at low levels (<10g/L) in up to 20% of patients