TWIST Score for Testicular Torsion Risk Stratification
What is the TWIST Score?
The TWIST (Testicular Workup for Ischemia and Suspected Torsion) score is a 7-point clinical decision tool that uses five physical examination findings to risk-stratify patients presenting with acute scrotal pain, helping determine which patients need immediate surgery, which need ultrasound, and which can safely avoid imaging. 1
Score Components
The TWIST score assigns points based on the following clinical findings 1, 2:
- Testicular swelling: 2 points
- Hard testis: 2 points
- Absent cremasteric reflex: 1 point
- Nausea/vomiting: 1 point
- High-riding testis: 1 point
Total possible score: 0-7 points 2
Risk Stratification Using the Barbosa System
The most accurate and validated approach uses the Barbosa stratification system, which divides patients into three risk categories 3:
Low Risk (TWIST Score 0-2)
- Negative predictive value: 98.5-100% 4, 5, 3
- These patients do NOT require ultrasound to rule out torsion 2
- Testicular torsion can be safely excluded in this group 3
- Represents approximately 65% of acute scrotum presentations 3
Intermediate Risk (TWIST Score 3-4)
- Sensitivity: 92.2%, Specificity: 68.2% 3
- Urgent Duplex Doppler ultrasound is recommended 1
- Represents approximately 20% of presentations 3
- Cannot reliably rule in or rule out torsion based on clinical findings alone 3
High Risk (TWIST Score 5-7)
- Positive predictive value: 61-93.5% 4, 2, 6
- Specificity: 94.5-97.5% 6, 3
- These patients should proceed directly to surgical exploration without delay for ultrasound 1, 2
- More than 50% of high-risk patients can avoid ultrasound and go straight to the operating room 2
- Represents approximately 15% of presentations 3
Diagnostic Performance
The TWIST score has an area under the curve of 0.924, indicating excellent diagnostic accuracy 3. The score performs well when assessed by both urologists and non-urological providers including emergency medical technicians and emergency department staff 2, 6.
Inter-rater reliability between emergency department and urology assessments is strong (rho = 0.71), confirming the score's reproducibility across different evaluators 6.
Clinical Application and Workflow
The TWIST score should be calculated at initial presentation, ideally during emergency department triage, before urological consultation 2. This allows for:
- Immediate surgical consultation for high-risk patients (score 5-7) without waiting for imaging 1, 2
- Targeted ultrasound use for intermediate-risk patients (score 3-4) 1, 3
- Reassurance and alternative diagnosis workup for low-risk patients (score 0-2) 2, 3
Important Caveats and Pitfalls
The TWIST score may underestimate risk in two specific scenarios 4:
- Very early presentation (within 6 hours of symptom onset): Physical examination findings may not yet be fully developed, potentially resulting in falsely low scores 4
- Partial torsion (<360 degrees): Patients with 180-degree torsion may have less dramatic physical findings but still require surgical intervention 4
A firm/hard testis on examination is particularly predictive of testicular necrosis requiring orchiectomy (OR 28.1), even after controlling for symptom duration 6. This finding should prompt urgent surgical exploration regardless of other score components.
The TWIST score reduces unnecessary ultrasound use by approximately 50% while maintaining excellent sensitivity for detecting torsion 5, 3. Per 100 presentations of acute scrotum using the Barbosa stratification, the missed torsion rate is only 1.6 cases, with an ultrasound rate of 19.9 cases and negative exploration rate of 2.5 cases 3.
Integration with Imaging
While the TWIST score is highly accurate, it should complement rather than replace clinical judgment 4. When ultrasound is performed for intermediate-risk patients, key findings include 1: