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Interference of M-protein on Thrombin Time Test: A Case Report
Milena Njegovan1, Sandra Margetić1, Andrea Tešija Kuna1
1Departments of Clinical Chemistry, Zagreb, Croatia.
Laboratory Medicine
|February 14, 2020
Summary
Monoclonal protein (M-protein) can interfere with thrombin time (TT) tests, leading to inaccurate results. This case highlights the importance of further diagnostic steps when coagulation screening tests show unexpected abnormalities.
Area of Science:
- Clinical Chemistry
- Hematology
- Immunology
Background:
- Coagulation screening tests are essential for assessing hemostasis.
- Monoclonal proteins can sometimes interfere with laboratory assays.
- Thrombin time (TT) is a critical parameter in coagulation diagnostics.
Observation:
- A 39-year-old male presented with significantly prolonged thrombin time (>150 seconds) and mildly elevated activated partial thromboplastin time (aPTT) (36 seconds).
- Initial coagulation factor assays did not reveal specific deficiencies.
- The patient had no clinical signs of bleeding or anticoagulant therapy.
Findings:
- Serum and urine protein electrophoresis with immunofixation identified monoclonal protein immunoglobulin G kappa (IgG kappa).
- The presence of M-protein was determined to be the cause of the aberrant TT and aPTT results.
- Specific coagulation factor levels were within normal limits, confirming M-protein interference.
Implications:
- Clinicians must consider M-protein interference when interpreting abnormal coagulation screening tests in the absence of clinical symptoms or anticoagulant use.
- Further diagnostic workup, including protein electrophoresis, is crucial for identifying the cause of unexpected coagulation test results.
- Accurate diagnosis prevents unnecessary treatment and guides appropriate patient management.
