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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.
Objective:
A case of interference of monoclonal protein (M-protein) on thrombin time (TT) test in a 39-year-old Caucasian male patient is presented.
Methods:
Coagulation screening tests were performed where altered results only for TT result (>150 seconds) and activated partial thromboplastin time (aPTT) result (36 seconds) were measured. Further specific coagulation testing included measurement of individual coagulation factors FII, FV, FVII, FVIII, FIX, FX, FXI, and FXII. Diagnostic steps in detection and identification of monoclonal protein included serum protein electrophoresis and immunofixation (both serum and urine specimen).
Results:
Monoclonal protein immunoglobulin G kappa detection and identification in serum and urine clarified the situation.
Conclusion:
Unexpectedly altered results of screening coagulation tests without any appropriate clinical signs and symptoms in a patient without any anticoagulant therapy needs to be critically considered in the context of extended next diagnostic steps in order to clarify the cause of pathological test results.
Insights
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.
