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Category Medicine & Tests

Symptoms

Migration of pain to RLQ M

1 pt

Anorexia A

1 pt

Nausea / Vomiting N

1 pt

Signs

RLQ Tenderness T

2 pts

Rebound Tenderness R

1 pt

Elevated Temperature (≥ 37.3°C) E

1 pt

Laboratory

Leukocytosis (WBC ≥ 10×10⁹/L) L

2 pts

Left Shift (Neutrophils > 75%) S

1 pt

/ 10

Appendicitis Unlikely

Select clinical findings above to calculate the Alvarado Score.

1-4

5-6

7-8

9-10

Unlikely Possible Probable Very Probable

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About

Misdiagnosis of acute appendicitis leads to either unnecessary surgery (negative appendectomy rate 15 - 25% historically) or delayed intervention risking perforation, peritonitis, and sepsis. The Alvarado Score, introduced by Dr. Alfredo Alvarado in 1986, quantifies appendicitis probability using 8 clinical and laboratory parameters weighted to a maximum of 10 points. The mnemonic MANTRELS encodes: Migration of pain, Anorexia, Nausea/vomiting, Tenderness in right lower quadrant, Rebound pain, Elevated temperature, Leukocytosis, and Shift of WBC to the left. A score ≥ 7 indicates probable appendicitis warranting surgical consultation. Scores of 5 - 6 suggest further imaging (CT or ultrasound). This tool does not replace clinical judgment. Sensitivity drops in elderly and pediatric populations. Pregnant patients require modified assessment due to cecal displacement.

Formulas

The Alvarado Score is a linear weighted sum of 8 binary clinical parameters:

A = M + A + N + 2T + R + E + 2L + S

Where each variable ∈ {0, 1} and:

M = Migration of pain to RLQ (1 point) • A = Anorexia (1 point) • N = Nausea or vomiting (1 point) • T = Tenderness in RLQ (2 points) • R = Rebound tenderness (1 point) • E = Elevated temperature (1 point) • L = Leukocytosis (2 points) • S = Shift of WBC to the left (1 point).

Risk stratification follows a piecewise classification:

{

Unlikely if A ≤ 4Possible if 5 ≤ A ≤ 6Probable if 7 ≤ A ≤ 8Very Probable if A ≥ 9

The total score range is 0 ≤ A ≤ 10. The 2-point parameters (RLQ tenderness and leukocytosis) carry double weight because they demonstrate the highest individual predictive value for appendicitis in validation studies.

Reference Data

Parameter	Mnemonic	Category	Points	Clinical Detail
Migration of pain to RLQ	M	Symptom	1	Periumbilical pain migrating to McBurney's point within 12 - 24h
Anorexia	A	Symptom	1	Loss of appetite; present in ∼80% of confirmed cases
Nausea / Vomiting	N	Symptom	1	Usually follows onset of pain; rarely precedes it
RLQ Tenderness	T	Sign	2	Maximal at McBurney's point (1/3 from ASIS to umbilicus)
Rebound Tenderness	R	Sign	1	Peritoneal irritation sign; suggests parietal peritoneum involvement
Elevated Temperature	E	Sign	1	Oral temperature ≥ 37.3°C (99.1°F)
Leukocytosis	L	Lab	2	WBC ≥ 10×10⁹/L
Left Shift of WBCs	S	Lab	1	Neutrophilia > 75% or band forms present
Maximum Total Score: 10
Score 1 - 4		Appendicitis unlikely. Discharge with follow-up instructions.
Score 5 - 6		Appendicitis possible. Recommend imaging (CT abdomen/pelvis or US).
Score 7 - 8		Appendicitis probable. Surgical consultation recommended.
Score 9 - 10		Appendicitis very probable. Urgent surgical intervention indicated.
Performance Metrics
Sensitivity (score ≥ 7)		72 - 87%
Specificity (score ≥ 7)		73 - 82%
PPV (score ≥ 7)		65 - 90% depending on prevalence
NPV (score ≤ 4)		93 - 98%

Frequently Asked Questions

Sensitivity drops to approximately 72 - 76% in children under 12 years. The Pediatric Appendicitis Score (PAS) by Samuel is often preferred for ages 4 - 15, as it replaces the left shift criterion with specific pain characteristics like cough/percussion/hopping tenderness. For children under 4, clinical presentation is often atypical and the score should not be relied upon.

Alvarado's original paper defined elevated temperature as oral temperature ≥ 37.3°C (99.1°F). Note this is a low-grade fever. High fever (> 39°C) actually suggests perforation or an alternative diagnosis such as pyelonephritis or pelvic inflammatory disease.

A score ≤ 4 has a negative predictive value of 93 - 98%, making it reasonably reliable for ruling out appendicitis. However, early appendicitis (within the first 6 - 12 hours) may not yet manifest leukocytosis or fever, producing a falsely low score. Serial examination at 6 - 8 hour intervals is recommended for patients with scores of 3 - 4.

Obesity reduces sensitivity of both RLQ tenderness and rebound tenderness assessment due to increased abdominal wall thickness. In patients with BMI > 30, CT imaging becomes particularly important regardless of score. Studies show the physical exam signs contribute less discriminatory power in obese patients, potentially underestimating the score by 1 - 2 points.

The Modified Alvarado Score (Kalan et al., 1994) removes the "Left Shift of WBCs" parameter, reducing the maximum score from 10 to 9. This modification was introduced because differential WBC count is not universally available in all emergency departments or resource-limited settings. The cutoff for probable appendicitis shifts to ≥ 7 out of 9. Performance is slightly lower but still clinically useful.

Yes. Scores of 5 - 6 represent the diagnostic gray zone where clinical findings alone are insufficient. CT abdomen/pelvis with IV contrast is the gold standard (sensitivity 94%, specificity 95%). Ultrasound is preferred in pregnant women and pediatric patients to avoid radiation. MRI is an alternative for pregnant patients when ultrasound is inconclusive.