What Does Low MA Mean on TEG?
A low Maximum Amplitude (MA) on thromboelastography indicates decreased clot strength, primarily reflecting thrombocytopenia, platelet dysfunction, or fibrinogen deficiency. 1, 2
Understanding Low MA
Maximum Amplitude (MA) represents the maximum strength of the clot and primarily reflects platelet function and fibrinogen concentration. 1, 2
Normal MA values typically range from 50-70 mm, with values <50 mm indicating significant clot strength impairment. 2
Decreased MA suggests thrombocytopenia, platelet dysfunction, or fibrinogen deficiency. 1, 2
Relative Contributions to Clot Strength
Fibrinogen contributes approximately 30-45% to overall clot strength (MA), while platelets contribute 55-70%. 3, 4, 5
The fibrinogen contribution to clot strength has a direct linear relationship with fibrinogen level (R = 0.83), meaning lower fibrinogen levels result in proportionally lower fibrinogen contribution. 4
Platelet count has only a moderate correlation to clot strength (R = 0.51), whereas functional fibrinogen has a stronger correlation (R = 0.80). 4
Clinical Significance
Low MA is associated with increased bleeding risk and higher transfusion requirements. 5
Coagulopathic patients have significantly lower fibrinogen contribution to MA compared to non-coagulopathic patients (24.7% vs. 31.2%). 5
Patients requiring plasma transfusion have significantly lower fibrinogen contribution to MA (26.6% vs. 30.6%). 5
Higher fibrinogen contribution to clot strength is predictive of reduced mortality (hazard ratio 0.815). 5
Diagnostic Approach
Use functional fibrinogen TEG to differentiate between fibrinogen and platelet contributions to the low MA. 2, 4
If functional fibrinogen TEG is unavailable, check conventional laboratory tests including platelet count and fibrinogen level to guide therapy. 2
A strong correlation exists between functional fibrinogen TEG and von Clauss fibrinogen levels (R = 0.87). 4
Treatment Algorithm
For Fibrinogen Deficiency:
If fibrinogen level <1.5-2.0 g/L or functional fibrinogen TEG shows decreased contribution, administer fibrinogen concentrate (first choice) at 25-50 mg/kg. 2
Alternative: administer 2 pools of cryoprecipitate (equivalent to 4g fibrinogen replacement). 2
Target fibrinogen level of at least 1.5-2.0 g/L in bleeding patients, with higher targets (>2.0 g/L) in obstetric hemorrhage. 2
For Thrombocytopenia or Platelet Dysfunction:
If platelet count <50,000/mm³ or there is evidence of platelet dysfunction, administer platelet transfusion (1 adult dose). 2
Target platelet count >50,000/mm³ for most bleeding scenarios. 2
Consider higher platelet count targets (>100,000/mm³) for patients with traumatic brain injury or requiring neurosurgery. 2
Monitoring Response
Repeat TEG 15-30 minutes after intervention to assess response. 2
Target MA normalization (typically >50 mm). 2
Important Pitfalls and Caveats
Standard TEG is insensitive to antiplatelet agents and cannot reliably detect platelet dysfunction. 1, 2, 6
Anemia can paradoxically show hypercoagulable TEG results due to decreased blood viscosity, potentially masking coagulopathy. 1, 2
Do not rely solely on conventional coagulation tests (PT, aPTT) as they may not correlate well with TEG parameters. 2
TEG shows high coefficients of variance (7.1-39.9% for TEG parameters), so results should be interpreted with caution and in clinical context. 1
Results vary between devices and are not interchangeable between TEG and ROTEM systems. 1
TEG cannot detect von Willebrand disease or disorders affecting endothelial adherence. 1
Special Considerations in Obstetrics
In pregnancy, baseline MA values are elevated due to physiologic hypercoagulability, so pregnancy-specific reference ranges must be used. 3
Abnormal TEG MA correlated with prolonged bleeding time, making TEG useful for assessing thrombocytopenia in pregnancy. 3
Low MA (≤54.2 mm) in pregnancy is associated with significantly high odds ratio of obstetric complications. 3