BC6062 Clinical Biochemistry (2024-2025)
A 90-year-old man who had a history of transurethral prostate resection for benign prostatic hyperplasia was admitted for left hip pain. A hip radiography examination revealed a large osteolytic lesion in the left greater trochanter, and a bone scintigraphy evaluation showed creased activity in the same area. Because of the patient’s history, metastasis from prostate carcinoma was suspected, and bone biopsies were performed the same week. Ten days later, the patient was hospitalised in the emergency department after a fall that fractured the femoral neck. At admission, plasma sodium, chloride, and potassium concentrations were all within their respective reference intervals.
Table 1: Laboratory Results
|
Test |
Result |
Reference Range |
|
Plasma concentration of total protein |
50.0 |
60-80 g/L |
|
Albumin |
15 |
30-45 g/L |
|
Corrected calcium |
2.69 |
2.25-2.65 mmol/L |
|
MCV |
95.1 |
80-97 fL |
|
Reticulocyte count |
54 |
25-80 X 109/L |
|
Hb |
9.9 |
13-17 g/dL |
|
WBCs |
2.5 |
4.0-10.0 X 109/L |
|
Creatinine |
97 |
62-106 mol/L |
|
Urea |
12.5 |
2.8-7.0 mmol/L |
|
Urine protein |
540 |
0-150 mg/24 h |
|
Free light chain |
14 |
0.0-2.0 mg/L |
|
Β2-microglobulin |
Normal |
|
Figure 1: (A) UPEP on concentrated urine protein, (B) Seum electrophoresis, and (C) Serum protein immunofixation.
The patient underwent surgical repair of his left femur, and the laboratory results after that procedure are shown below.
Table 2: Laboratory Results
|
Test |
Results |
Reference Range |
|
Albumin |
14.5 |
30-45 g/L |
|
IgG |
29.5 |
7-10 g/L |
Serum protein electrophoresis (SPEP) showed
1) an increased α1 region and decreased albumin and γ regions.
2) An increase in the β region
Figure 2: Immunofixation of Serum (S) and urine (U) proteins.
Serum immunofixation:
1) monoclonal protein concentration 16 g/L
2) decreased free k chain of 0.6 mg/L (Ref. Range 3.3-19.4 mg/L)
3) decreased free λ chain 0.45 mg/L (Ref. Range 5.7-26.3) mg/L)
4) k/λ ratio 1.33 (Ref. Range 0.26-1.65)
IgG subclass qualifications
1) IgG1 7.68 (ref Range 5-8 g/L)
2) IgG2 <9.0 (ref Range 0.9-3.0 g/L)
3) IgG3 0.23 (ref Range 0.1-0.8 g/L)
4) IgG4 0.01 (ref range 0.1-0.6 g/L)
Questions
1) What are the potential causes of increased β-globulins?
2) What can explain the discrepancy between the presence of k light chains in the urine and a monoclonal IgG without light chains in the serum?
3) What investigations should be performed to characterise the protein responsible for the spike in the β region of the urine electrophoresis results?
4) What can explain the observation that the sum of the 4 IgG subclasses <8 g/L) was not equal to the total IgG concentration of 29.5 g/L?