What Does Low MA Mean on TEG?
Low Maximum Amplitude (MA) on thromboelastography indicates reduced clot strength, primarily reflecting thrombocytopenia, platelet dysfunction, or fibrinogen deficiency, and is independently associated with increased bleeding risk, higher transfusion requirements, and increased mortality. 1, 2, 3
Understanding Low MA
- MA represents the maximum strength of the formed clot, with normal values typically ranging from 50-70 mm 1, 2
- Values <50 mm indicate significant clot strength impairment and are associated with increased 30-day mortality in trauma patients (47% vs. 10% mortality, p < 0.001) 1, 3
- Fibrinogen contributes approximately 30-45% to overall clot strength, while platelets contribute 55-70% 2, 4
Clinical Significance
- Low MA correlates directly with blood product requirements in the first 24 hours after admission 5, 3
- Patients with reduced MA require significantly more packed red blood cells, fresh frozen plasma, and platelet concentrates 3
- Coagulopathic patients (INR ≥1.3) have significantly lower MA values (24.7% vs. 31.2% fibrinogen contribution, p < 0.05) 4
- Low MA is a more accurate indicator of transfusion requirements than conventional coagulation tests (PT, aPTT, INR) in trauma patients 5
Diagnostic Approach to Low MA
When you encounter low MA, follow this algorithmic approach:
Check functional fibrinogen TEG (if available) to differentiate between fibrinogen and platelet contributions 1, 2
If functional fibrinogen TEG is unavailable, obtain conventional laboratory tests:
Recognize that the product of platelet count × fibrinogen concentration correlates most strongly with MA (r = 0.91) compared to either value alone 6
Treatment Algorithm
Base your treatment on the underlying cause:
If Platelet-Related (platelet count <50,000/mm³ or platelet dysfunction):
- Administer 1 adult dose of platelet transfusion 1
- Target platelet count >50,000/mm³ for most bleeding scenarios 1
- Target >100,000/mm³ for traumatic brain injury or neurosurgery 1
If Fibrinogen-Related (fibrinogen <1.5-2.0 g/L):
- First-line: Administer fibrinogen concentrate at 25-50 mg/kg 1, 2
- Alternative: 2 pools of cryoprecipitate (equivalent to 4g fibrinogen replacement) 1
- Target fibrinogen level ≥1.5-2.0 g/L in bleeding patients 1, 2
- Higher targets (>2.0 g/L) may be needed in obstetric hemorrhage 1
Monitoring Response:
- Repeat TEG 15-30 minutes after intervention to assess response 1, 2
- Target MA normalization to ≥50 mm 1, 2
Critical Pitfalls to Avoid
- Do not rely solely on PT/aPTT/INR - these conventional tests do not correlate well with TEG parameters and are less predictive of transfusion needs 5
- Standard TEG is insensitive to antiplatelet agents and cannot reliably detect platelet dysfunction, so do not use it to rule out platelet problems in patients on antiplatelet therapy 7, 1, 2
- Anemia can paradoxically show hypercoagulable TEG results due to decreased blood viscosity, potentially masking underlying coagulopathy 1, 2
- TEG cannot detect von Willebrand disease or any conditions affecting endothelial adherence, as it bypasses primary hemostasis 7
- Do not use TEG alone to assess platelet function - supplement with more sensitive platelet tests if platelet dysfunction is suspected 7
- Recognize high test variability - TEG has coefficients of variance ranging from 7.1% to 39.9%, so interpret results in clinical context 1, 2
Special Clinical Contexts
In Pregnancy:
- Use pregnancy-specific reference ranges - baseline MA values are elevated due to physiologic hypercoagulability 2
- Low MA in pregnancy (≤54.2 mm) is associated with significantly increased odds of obstetric complications 2
In Trauma:
- Low MA is an independent predictor of mortality after adjusting for age and injury severity score 3
- A biphasic relationship exists: MA increases linearly with platelet count up to 90 × 10⁹/L, then plateaus above 100 × 10⁹/L 6
- A platelet count of 60 × 10⁹/L is associated with a TEG-MA of 53 mm (just above the critical threshold) 6