What is the appropriate management for an abnormal plasmic score related to coagulation?

PLASMIC Score: Clinical Application and Management

What is the PLASMIC Score?

The PLASMIC score is a validated clinical prediction tool designed to rapidly identify patients with suspected thrombotic thrombocytopenic purpura (TTP) who have severe ADAMTS13 deficiency (<10% activity), enabling immediate therapeutic decisions before confirmatory laboratory results are available. 1, 2

The score comprises 7 clinical and laboratory parameters:

• Platelet count <30×10⁹/L (1 point)
• Absence of active cancer or Lack of cancer (1 point)
• Absence of solid organ or stem cell transPlant (1 point)
• MCV <90 fL (1 point)
• INR <1.5 (1 point)
• Serum creatinine <2 mg/dL (1 point)
• Hemolysis present (1 point)

Total scores range from 0-7 2, 3

Risk Stratification and Clinical Interpretation

High-Risk Group (PLASMIC Score 6-7)

• 60-72% positive predictive value for severe ADAMTS13 deficiency 1, 2
• 100% of patients with score 7 have ADAMTS13 <5% 2
• Sensitivity of 90% and specificity of 92% when dichotomized at ≥6 1
• These patients require immediate therapeutic plasma exchange (TPE) without waiting for ADAMTS13 results 4, 5

Intermediate-Risk Group (PLASMIC Score 5)

• Only 5.9% have severe ADAMTS13 deficiency 2
• A threshold of ≥5 demonstrates sensitivity of 99% and NPV of 99% 5
• Consider empiric TPE while awaiting ADAMTS13 results in clinically unstable patients 1

Low-Risk Group (PLASMIC Score 0-4)

• Essentially rules out TTP with NPV approaching 100% 2, 5
• No significant survival benefit from plasma exchange in this group 1
• Pursue alternative diagnoses for thrombotic microangiopathy 3

Management Algorithm Based on PLASMIC Score

For PLASMIC Score 6-7 (High Risk):

Initiate therapeutic plasma exchange immediately without waiting for ADAMTS13 confirmation 1, 5

• Start daily TPE (1-1.5 plasma volumes) 4
• Continue until platelet count >150×10⁹/L for 2 consecutive days and LDH normalizing 4
• Add corticosteroids (prednisone 1 mg/kg daily) 4
• Consider rituximab for refractory cases 4

For PLASMIC Score 5 (Intermediate Risk):

• Assess clinical severity and organ dysfunction 1
• If hemodynamically unstable or neurologic symptoms present: initiate empiric TPE 5
• If stable: closely monitor while awaiting ADAMTS13 results 3
• Avoid delays >24 hours in decision-making 4

For PLASMIC Score 0-4 (Low Risk):

Do not initiate plasma exchange; investigate alternative causes of thrombotic microangiopathy 1, 5

Alternative diagnoses to consider:

• Disseminated intravascular coagulation (DIC) - check fibrinogen, PT/aPTT, D-dimer 6, 7
• Hemolytic uremic syndrome - assess for diarrheal prodrome, Shiga toxin 5
• Drug-induced TMA - review medication history 3
• Malignancy-associated microangiopathy 2

Critical Distinctions: TTP vs DIC

When PLASMIC score is low but coagulopathy persists, consider DIC:

DIC Diagnostic Features (vs TTP):

• Fibrinogen typically <1.5 g/L in DIC but normal in TTP 6, 7
• PT/aPTT prolonged in DIC, normal in TTP 7
• Platelet counts moderately reduced in DIC (rarely <20×10⁹/L), profoundly low in TTP 7
• Clinical context: sepsis, trauma, malignancy, obstetric complications favor DIC 7

DIC Management (When PLASMIC Score Rules Out TTP):

• Treat underlying condition as cornerstone of therapy 6, 7
• Maintain platelets >50×10⁹/L if active bleeding 6, 8
• Transfuse fresh frozen plasma 15-30 mL/kg for active bleeding with prolonged coagulation times 6, 7
• Replace fibrinogen with cryoprecipitate if <1.5 g/L despite FFP 6, 7
• Consider prophylactic heparin in thrombotic-predominant DIC (contraindicated if platelets <20×10⁹/L or active bleeding) 6, 9

Common Pitfalls and Caveats

Pitfall 1: Missing Data Elements

• PLASMIC score requires all 7 variables; incomplete data reduces diagnostic accuracy 1
• Obtain complete laboratory panel including MCV, INR, creatinine before calculating score 2

Pitfall 2: Over-reliance on Score Alone

• Completely asymptomatic presentations of TTP can occur despite high PLASMIC scores 4
• Clinical judgment remains essential; score is adjunctive, not definitive 5

Pitfall 3: Threshold Selection

• PLASMIC score <6 has insufficient sensitivity to definitively rule out TTP 5
• Use threshold ≥5 for screening (high NPV 99%), but ≥6 for treatment decisions 5

Pitfall 4: Delayed Treatment in High-Risk Patients

• Mortality increases significantly with delayed TPE initiation 4
• Do not wait for ADAMTS13 results when PLASMIC score is 6-7 1, 2

Pitfall 5: Confusing DIC with TTP

• Normal fibrinogen and PT/aPTT strongly favor TTP over DIC 7
• Fresh frozen plasma is therapeutic in TTP but only supportive in DIC 10, 7

Performance Characteristics

The PLASMIC score demonstrates:

• AUC ROC of 0.86-0.94 across validation studies 2, 3
• Sensitivity 92% and specificity 79% for severe ADAMTS13 deficiency 2
• Excellent generalizability with fewer missing data than alternative clinical scores 1