Alvarado Score in Diagnosing Acute Appendicitis
The Alvarado score is a validated clinical tool that effectively excludes appendicitis at low scores (<5) with 99% sensitivity, but lacks sufficient specificity to confirm the diagnosis and should primarily guide decisions about imaging and observation rather than surgical intervention. 1, 2
What the Alvarado Score Measures
The score combines clinical and laboratory parameters totaling 0-10 points 1, 2:
Symptoms (3 points total):
- Migration of pain to right lower quadrant (1 point)
- Anorexia (1 point)
- Nausea/vomiting (1 point)
Signs (3 points total):
- Right lower quadrant tenderness (2 points)
- Rebound tenderness (1 point)
Laboratory findings (4 points total):
- Elevated WBC >10,000/mm³ (2 points)
- Left shift/neutrophilia (1 point)
- Elevated temperature >37.3°C (1 point) 2
Risk Stratification and Clinical Utility
Low Risk (Score 0-4):
- Only 5% of patients have appendicitis 1, 2
- These patients can be safely discharged without imaging 1, 2
- No patients with scores ≤1 (males) or ≤2 (females) had appendicitis in large cohorts 1
- This is where the score performs best—ruling out disease 1, 2
Intermediate Risk (Score 5-6):
- 30-36% have appendicitis 1, 2
- CT imaging is strongly recommended for this group 1, 2
- This equivocal range lacks diagnostic certainty and requires objective imaging 1, 3
High Risk (Score 7-10):
- 78-98% have appendicitis 1, 2
- Scores ≥9 in males and ≥10 in females approach 100% positive predictive value 1
- Surgical consultation should precede imaging in this group 1
- However, imaging may still be valuable to assess for complications 1
Critical Limitations
The score cannot be used alone to confirm appendicitis because specificity is only 43-69% 1, 2. Multiple studies demonstrate this weakness:
- One study found 72% of patients with scores 1-4 ultimately had appendicitis on CT and surgery 1
- Another found 8.4% of confirmed appendicitis cases had scores <5 1
- Clinical judgment outperformed the Alvarado score in head-to-head comparison 4
Population-specific failures:
- Unreliable at age extremes: Patients 0-10 years and 60-80 years are frequently misdiagnosed 1, 2
- Cannot differentiate complicated from uncomplicated appendicitis in elderly patients 1
- Less sensitive in HIV+ patients 1
- Less accurate in women due to gynecologic differential diagnoses 5
Practical Clinical Algorithm
For scores 0-4:
For scores 5-6:
- Obtain CT abdomen/pelvis with IV contrast 2
- If contraindicated, use MRI or non-contrast CT 2
- Consider observation with serial examinations if imaging unavailable 3
For scores 7-10:
- Obtain surgical consultation 1
- Consider CT to assess for perforation/complications before surgery 1
- In males with score ≥9 or females with score ≥10, proceed directly to surgery 1
Special considerations:
- Elderly patients (≥60 years) with scores ≥5: Always obtain CT due to high perforation risk and score unreliability 2
- Pregnant patients: Never rely on score alone; always obtain laboratory tests and consider ultrasound first 1
- Children: Use Pediatric Appendicitis Score instead; standard Alvarado less reliable 1
Superior Alternative Scores
The AIR (Appendicitis Inflammatory Response) score and Adult Appendicitis Score (AAS) outperform Alvarado with better sensitivity (92%) and specificity (63%) 1. The 2020 WSES Jerusalem Guidelines give these scores a strong 1A recommendation while suggesting against using Alvarado to positively confirm appendicitis (weak 2B recommendation) 1.
Common Pitfalls to Avoid
- Never use the score alone to send a patient to surgery—specificity is too low 1, 6
- Don't skip imaging in intermediate scores (5-6)—this group has the most diagnostic uncertainty 1, 2
- Don't trust low scores in elderly patients—they present atypically despite advanced disease 1, 2
- Don't assume high scores mean uncomplicated appendicitis—perforation risk assessment requires imaging 1
- Beware of confounding conditions like UTI that cause leukocytosis and fever, artificially elevating scores 7