Question

Case #9

A 53-year-old male patient with an established diagnosis of IgG ? multiple myeloma was seen by a hematologist–oncologist in consultation from an outside hospital. He had previously received 1 cycle of chemotherapy treatment, but he was found to be

Intermittently noncompliant with his therapy. The patient reported occasional nosebleeds and fatigue. Except for a slightly cachectic appearance, the physical examination was unremarkable. Laboratory results are shown in Table 1.

Serum protein electrophoresis revealed monoclonal paraproteinemia in high abundance marked by an intense band in the ? region. Immunofixation electrophoresis was not ordered at that time, but it was previously performed at another institution and was positive for IgG monoclonal protein.

The attending pathologist noted the discrepancy between the presence of a monoclonal band by serum protein electrophoresis and the patient’s quantitative immunoglobulin measurements. Several additional suspicious test results were also noted.

Laboratory Test	Reference interval	Result
IgG	700-1700 mg/dL	<140 mg/dL
IgA	70.0-450.0 mg/dL	<5.0 mg/dL
IgM	50-250 mg/dL	<21 mg/dL
Sodium	135-145 mmol/L	124 mmol/L
Potassium	3.6-5.1 mmol/L	5.2 mmol/L
Chloride	100-110 mmol/L	102 mmol/L
Carbon Dioxide	21-33 mmol/L	22 mmol/L
Creatinine	0.60-1.20 mg/dL	2.54 mg/dl
Blood urea Nitrogen	8-23 mg/dL	36 mg/dL
Glucose	65-100 mg/dL	96 mg/dL
Total calcium	8.9-10.7 mg/dL	9.2 mg/dL
Total Protein	6.4-8.5 g/dL	18.4 g/dL
Inorganic phosphate	2.50-4.60	14.49 mg/dL
WBC count	3.7-9.7x10^9/L	4.7x10^9
Hemoglobin	13.3-17.2 g/dL	8.2 g/dL
Hematocrit	38.9%-50.9%	24.6%
Platelet count	179-373x10^9/L	104x10^9/L
Mean corpuscular volume	81.2-94.0 fL	91.6 fL

1. What are some expected laboratory results in a patient with multiple myeloma?

2. Which of the patient’s laboratory test results are unexpected given his diagnosis of multiple myeloma?

3. What types of laboratory errors can occur in patients with multiple myeloma?

Answer 1

1. Some expected lab results for multiple myeloma are:

• Increased serum globulins or immunoglobulins
• Presence of paraprotein or M protein
• Increased creatinine
• Increased ESR
• anemia causing low haemoglobin
• High serum protein
• High serum calcium due bone degradation and osteoporosis

?2. Multiple myeloma is characterised by high level of immunoglobulin. High level of proteins should be associated with high immunoglobulins. But these results show decreased immunoglobulins.

3. The low immunoglobins can be due to three reasons:

• Immunoturbidimetric methods are subject to interference via the prozone effect, in which excess antigen inhibits stable antigen–antibody complex formation, resulting in decreased absorbance and a falsely low result. Detection of the prozone effect requires sample dilution.

• The volume displacement effect is caused by increased concentrations of protein or lipids which displace aqueous components of blood. This effect can be avoided by utilizing direct potentiometry in which electrolyte measurements are evaluated in an undiluted plasma sample.

• Spectrophotometric quantification of serum inorganic phosphate concentrations may give falsely increased results owing to immunoglobulin precipitation. Resolution of pseudohyperphosphatemia is obtained by diluting the sample, thereby reducing the quantity of plasma proteins