Cellulitis Diagnosis and Lab Testing
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Cellulitis Diagnosis and Lab Testing

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Questions and Answers

What is the most common method for diagnosing cellulitis?

  • Serologic tests
  • Clinical history and physical examination (correct)
  • Laboratory testing
  • Imaging studies

    • What percentage of patients with cellulitis exhibit leukocytosis?

  • Over 80%
  • 34% to 50% (correct)
  • Up to 10%
  • 60% to 70%

    • Which inflammatory marker is elevated in more than 75% of cellulitis patients?

  • C-reactive protein (correct)
  • Procalcitonin
  • Erythrocyte sedimentation rate
  • Leukocyte count

    • What is a significant consequence of misdiagnosing cellulitis in acute care settings?

    <p>Avoidable healthcare spending</p> Signup and view all the answers

    What role does consulting a dermatologist play in the diagnosis of cellulitis?

    <p>Improves diagnostic accuracy and shortens antibiotic use</p> Signup and view all the answers

    When do Antistreptolysin O responses typically peak in cutaneous infections?

    <p>3 to 6 weeks</p> Signup and view all the answers

    What is the likelihood of blood cultures being positive in uncomplicated cellulitis?

    <p>5%</p> Signup and view all the answers

    What is the recommended action for pustules or abscesses associated with purulent cellulitis?

    <p>Drain and culture them early</p> Signup and view all the answers

    In which patient population should blood cultures generally be drawn before routine diagnostics?

    <p>Immunocompromised individuals</p> Signup and view all the answers

    What is the positive yield rate of skin biopsies for tissue culture in evaluating cellulitis?

    <p>20% to 30%</p> Signup and view all the answers

    What imaging technique can help identify localized fluid collections in purulent cellulitis?

    <p>Ultrasonography</p> Signup and view all the answers

    Which new diagnostic prediction model can help predict lower-extremity cellulitis?

    <p>ALT-70 model</p> Signup and view all the answers

    What minimum leukocyte count is associated with the ALT-70 predictive model for cellulitis?

    <p>10,000 cells/μL</p> Signup and view all the answers

    Which method has shown promise in differentiating cellulitis using skin surface temperature gradient?

    <p>Thermal imaging</p> Signup and view all the answers

    What histopathologic findings are commonly seen in cellulitis?

    <p>Sparse perivascular lymphocytic infiltrate with edema</p> Signup and view all the answers

    Study Notes

    Cellulitis Diagnosis

    • Most cellulitis diagnoses are made through clinical history and physical examination, as there are no reliable diagnostic studies.
    • The four cardinal signs are: erythema (redness), swelling, warmth, and pain.
    • Pseudocellulitis can mimic the signs of cellulitis, leading to misdiagnosis.
    • Misdiagnosis rates are high, exceeding 30% in acute care settings.
    • Consultations with dermatologists improve diagnostic accuracy and clinical outcomes.

    Laboratory Testing

    • Leukocytosis (high white blood cell count) is present in 34% to 50% of patients.
    • Inflammatory markers like erythrocyte sedimentation rate and C-reactive protein are elevated in over 75% of patients, but these findings are not specific to cellulitis.
    • Procalcitonin, a biomarker used for serious systemic bacterial infections, has inconsistent usefulness in cellulitis.
    • Serologic tests are controversial, as they may not differentiate acute infection from prior exposure.
    • Antistreptolysin O levels are more limited in cutaneous infections than respiratory infections, and their timing can be problematic for diagnosis.
    • The anti-DNase B test peaks later than is useful for acute clinical decision-making.

    Microbial Culture

    • Skin swabs and wound cultures are often unhelpful due to polymicrobial nature and difficulty distinguishing colonization from true pathogenicity.
    • MRSA carriage detected by polymerase chain reaction (PCR) swabs may correlate with increased cellulitis risk, but their usefulness in acute infection is debatable.
    • Needle aspiration with culture has varying diagnostic usefulness, potentially more helpful in patients with systemic risk factors.
    • Blood cultures are not routinely performed in uncomplicated cellulitis as they are positive in only about 5% of cases.
    • Blood cultures are recommended in high-risk populations, such as the elderly, immunocompromised, systemically ill, or those with penetrating trauma.
    • The IDSA guidelines do not routinely recommend culturing blood or aspirates/swabs, but advise drainage and culture for purulent cellulitis.

    Pathology

    • Biopsy is not routinely performed due to nonspecific histopathologic findings.
    • Biopsy findings include sparse to moderately dense perivascular lymphocytic infiltrate with neutrophils, sometimes with dermal edema.
    • Gram stains are frequently negative.
    • Skin biopsy can be helpful for pseudocellulitis, depending on the etiology.
    • Tissue culture is not routinely recommended, as biopsies are positive in only 20% to 30% of cases.
    • Biopsy for histopathologic evaluation and tissue culture is indicated if atypical organisms, including mycobacteria, fungi, or viruses, are suspected or in high-risk populations.
    • Molecular techniques like PCR are not reliable for differentiating involved from uninvolved skin and are often negative.

    Imaging

    • Imaging is not diagnostic for uncomplicated cellulitis.
    • Ultrasonography and MRI can help locate fluid collections for incision and drainage, and MRI can identify deeper tissue involvement like pyomyositis or osteomyelitis.
    • CT or MRI can distinguish cellulitis from necrotizing soft-tissue infections.

    Emerging Diagnostic Modalities

    • The ALT-70 risk prediction model helps predict the likelihood of lower-extremity cellulitis.
    • Thermal imaging, measuring skin temperature gradients, shows promise with high sensitivity but needs more confirmation.
    • Genetic testing, particularly HLA-DQA1 expression, has potential for cellulitis diagnosis.

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    Description

    This quiz focuses on the diagnosis of cellulitis, emphasizing clinical history, examination, and laboratory testing. Learn about the cardinal signs of cellulitis, misdiagnosis rates, and the role of inflammatory markers. Enhance your understanding of diagnostic challenges and the importance of specialist consultations.

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