ALT-70 Score for Cellulitis

Why Use

Cellulitis is the most common skin and soft tissue infection, with a high cost. No gold-standard diagnostic test exists, and clinical signs of redness, edema, warmth, and tenderness are nonspecific. At least 30% of patients with presumed cellulitis are misdiagnosed, leading to unnecessary admissions, overuse of antibiotics, and missed alternative diagnoses. Factors previously used to determine likelihood of true cellulitis (e.g. past medical and skin history, prior cellulitis, ulcers, barrier disruption, tinea, lymphedema, venous disease, malignancy, and underlying dermatitis) have not been shown to be statistically significant risk factors for cellulitis. May also help indicate appropriate subspecialty consultation to identify pseudocellulitis/mimickers.

When to Use

Adult patients presenting to the ED with a red leg and clinical concern for cellulitis. Do not use if any of the following: Visible abscess/fluctuance. Penetrating trauma. Burn. Diabetic ulcer. Implanted hardware/device. Post-operative patient. Recent (within 48 hours) IV antibiotic use.

Formula

Pearls / Pitfalls

Developed to assist with evaluation of lower extremity redness, which may be inappropriately diagnosed as cellulitis (versus mimickers, or “pseudocellulitis”). Most patients with cellulitis have acute onset, unilateral involvement (usually one leg), and are sick with an elevated white blood cell count, tachycardia, and/or a fever. Validated in a small cohort of 67 patients ( Li 2018 ).

Management

Patients with true cellulitis should be treated with standard-of-care management, which varies based on their underlying disease state, recent antibiotics or previously documented microbial culture data, and local antibiotic resistant patterns. This may include oral or IV antibiotics. Patients with pseudocellulitis (mimickers) should be treated appropriately for the identified alternate diagnosis.

Critical Actions

Patients with septic physiology may require more immediate attention and aggressive intervention. Patients with fluctuant lesions/abscesses may require imaging and/or surgical intervention.

Advice

Scores 5-7 indicate likely cellulitis (>82.2% likelihood), and patients should receive appropriate therapy. This may vary based on comorbidities or underlying diseases, history of resistant organisms, prior culture data or prior antibiotic use, and/or whether there is a clear trigger or portal of entry. Scores 3-4 indicate uncertainty, and consultation may be appropriate. Dermatology consultation may assist in the evaluation and can help identify alternative etiologies or explanations; if not available, ID consultation may be appropriate. Examples of alternative etiologies include: Vascular inflammation, stasis dermatitis. Inflammatory skin conditions. Alternate infections (e.g. Lyme). Chemotherapeutic reactions. Contact dermatitis. Scores 0-2 suggest patients are unlikely to have true cellulitis (likelihood of pseudocellulitis >83.3%) and should be reassessed to have the differential diagnosis reconsidered. Very common mimickers include: Bilateral redness without tachycardia/leukocytosis in a patient with edema and/or heart failure, suggestive of stasis dermatitis. Pruritic, geometric patch with serous drainage in someone using a topical agent who may have developed allergic contact dermatitis.

More Information

Interpretation: ALT-70 Score Recommendation 0-2 Reassess (>83.3% likelihood of pseudocellulitis) 3-4 Consult dermatology and/or infectious disease 5-7 Treat (>82.2% likelihood of true cellulitis)