Calc Function

    • Calcs that help predict probability of a diseaseDiagnosis
    • Subcategory of 'Diagnosis' designed to be very sensitiveRule Out
    • Disease is diagnosed: prognosticate to guide treatmentPrognosis
    • Numerical inputs and outputsFormula
    • Med treatment and moreTreatment
    • Suggested protocolsAlgorithm





    Chief Complaint


    Organ System


    Patent Pending

    ALT-70 Score for Cellulitis

    Predicts likelihood of lower extremity cellulitis over other diagnoses.


    Use in adult patients presenting to the ED with a red leg and clinical concern for cellulitis. Do not use if: visible abscess/fluctuance, penetrating trauma, burn, diabetic ulcer, hardware/device, post-operative patient, or recent (within 48 hrs) IV antibiotic use.

    When to Use
    Why 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.

    • 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).

    • 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.



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    Next Steps
    Creator Insights


    • 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.


    • 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.


    Addition of the selected points:





    Age ≥70 years


    WBC in ED ≥10,000/µL


    HR in ED ≥90 bpm


    Facts & Figures


    ALT-70 Score



    Reassess (>83.3% likelihood of pseudocellulitis)


    Consult dermatology and/or infectious disease


    Treat (>82.2% likelihood of true cellulitis)


    Other References

    Research PaperWeng QY, Raff AB, Cohen JM, et al. Costs and Consequences Associated With Misdiagnosed Lower Extremity Cellulitis. JAMA Dermatol. 2016.Research PaperArakaki RY, Strazzula L, Woo E, Kroshinsky D. The impact of dermatology consultation on diagnostic accuracy and antibiotic use among patients with suspected cellulitis seen at outpatient internal medicine offices: a randomized clinical trial. JAMA Dermatol. 2014;150(10):1056-61.Research PaperStrazzula L, Cotliar J, Fox LP, et al. Inpatient dermatology consultation aids diagnosis of cellulitis among hospitalized patients: A multi-institutional analysis. J Am Acad Dermatol. 2015;73(1):70-5.Research PaperLevell NJ, Wingfield CG, Garioch JJ. Severe lower limb cellulitis is best diagnosed by dermatologists and managed with shared care between primary and secondary care. Br J Dermatol. 2011;164(6):1326-8.Research PaperRaff AB, Kroshinsky D. Cellulitis: A Review. JAMA. 2016;316(3):325-37.
    Dr. Adam B. Raff

    About the Creator

    Adam B. Raff, MD, PhD, is a dermatologist at Harvard Medical School. He is also an instructor in dermatology at Massachusetts General Hospital. Dr. Raff’s primary research is focused on infectious skin diseases, skin cancer, and eczema.

    To view Dr. Adam B. Raff's publications, visit PubMed

    Dr. Arash Mostaghimi

    About the Creator

    Arash Mostaghimi, MD, MPA, MPH, is the director of Dermatology Inpatient Service and co-director of the Complex Medical Dermatology Fellowship Program at Brigham and Women's Hospital. He is also an associate professor at Harvard Medical School. Dr. Mostaghimi’s primary research is focused on severe drug reactions, cutaneous oncology, and medical dermatology.

    To view Dr. Arash Mostaghimi's publications, visit PubMed

    Dr. Qing Yu Christina Weng

    About the Creator

    Qing Yu Christina Weng, MD, is a dermatology resident at the Harvard Combined Dermatology Residency training program. Her research is in melanocyte biology, which she began in the laboratory of David Baltimore at the California Institute of Technology and continued in the laboratory of David Fisher during medical school at Harvard. Dr. Weng completed a research fellowship supported by the Howard Hughes Medical Institute and is currently in the accelerated research track in residency, with a research and clinical focus on melanoma and pigment biology.

    To view Dr. Qing Yu Christina Weng's publications, visit PubMed

    Content Contributors
    • Misha Rosenbach, MD
    Content Contributors
    • Misha Rosenbach, MD