Unit Converter
Prothrombin Time Quick
(Percent Activity Measure of Extrinsic & Common Pathway - Used for Liver Function, Vitamin K Status & Historical Warfarin Monitoring)
Synonyms
- PT Quick
- Quick’s Prothrombin Time
- Prothrombin Time Activity
- Quick %
- Prothrombin Activity (%)
- PT Ratio
- PT Fraction
Units of Measurement
- % (percent activity)
- Ratio
- Fraction
Key Relationships
\text{PT Quick %} = \frac{\text{Normal PT}}{\text{Patient PT}} \times 100 PT Ratio=Patient PTNormal PT\text{PT Ratio} = \frac{\text{Patient PT}}{\text{Normal PT}}PT Ratio=Normal PTPatient PT \text{PT Fraction} = \frac{\text{PT Quick %}}{100}
Description
Prothrombin Time – Quick (PT Quick) expresses prothrombin activity as a percent, instead of the clotting time in seconds.
PT Quick historically preceded the adoption of INR, especially in Europe.
It reflects activity of:
- Factor VII (extrinsic pathway)
- Factors II, V, X & fibrinogen (common pathway)
Low PT Quick % = prolonged PT
High PT Quick % = normal / faster clotting
PT Quick is commonly used in:
- Liver disease assessment
- Vitamin K deficiency
- Preoperative screening
- Warfarin therapy (older systems / Europe)
Physiological Basis
The value shows how well the clotting system works:
- 100% = normal prothrombin activity
- <70% = impaired activity
- <40% = high bleeding risk
Clinical Significance
LOW PT Quick % (Most Important Finding)
Indicates impaired clotting → prolonged PT.
Major Causes
1. Vitamin K Deficiency
- Malnutrition
- Fat malabsorption
- Antibiotics
- Cholestasis / biliary obstruction
2. Warfarin Therapy
Directly decreases factors II, VII, IX, X → lowers Quick %.
3. Liver Disease
Reduced synthesis of clotting factors:
- Cirrhosis
- Acute liver failure
- Chronic hepatitis
4. DIC (Disseminated Intravascular Coagulation)
5. Factor Deficiencies
- II, V, VII, X deficiencies
6. Massive Transfusion (dilutional coagulopathy)
HIGH PT Quick %
Represents normal or enhanced coagulation activity.
Values >100% may occur with reagent variability but have no pathological significance.
Reference Intervals
PT Quick (%)
- 70 – 130% (typical reference range)
Depends on reagent calibration.
Interpretation Ranges
| PT Quick (%) | Meaning |
| >70% | Normal coagulation activity |
| 40–70% | Mild–moderate deficiency |
| 20–40% | Significant clotting impairment |
| <20% | Severe deficiency, high bleeding risk |
PT Ratio
- Normal: 0.8 – 1.2
PT Fraction
- 0.70 – 1.30 (same as Quick% divided by 100)
Diagnostic Uses
1. Liver Function Assessment (PRIMARY USE outside warfarin)
PT Quick is one of the best markers of liver synthetic function.
2. Vitamin K Deficiency
Early and sensitive.
3. Warfarin Therapy Monitoring
Now largely replaced by INR, but still used in some regions.
4. Preoperative Evaluation
Useful when bleeding risk is suspected.
5. DIC Evaluation
PT Quick falls with consumption of clotting factors.
6. Factor VII Deficiency
Shows isolated prolonged PT (Quick ↓).
Analytical Notes
- Citrated plasma required
- Underfilling tube → falsely low Quick % (prolonged PT)
- Thromboplastin reagent variation affects range
- PT Quick should not be used for DOAC monitoring
- INR is now the standard for warfarin therapy worldwide
Clinical Pearls
- PT Quick <40% is a strong predictor of bleeding in liver disease.
- Quick % correlates with Factor VII due to its short half-life.
- In vitamin K deficiency, PT Quick improves rapidly after vitamin K injection (8–12 hours).
- Always interpret Quick % with INR if the patient is on warfarin.
- Quick % is particularly useful in European and older laboratory systems.
Interesting Fact
Quick’s test was introduced by Armand Quick in 1935, long before INR existed. Many European labs still report PT as a percentage activity (Quick %).
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Coagulation Testing
- ISTH - Coagulation Standardization Guidelines
- ACCP - Anticoagulation Therapy Guidelines
- Mayo Clinic Laboratories - PT & Quick Test
- ARUP Consult - Coagulation Evaluation
- MedlinePlus / NIH - PT/Coagulation Test