Scabies: Refine your exam, avoid these diagnostic pitfalls
Nearly half of all infections are missed when first examined. Attentiveness to specific details, particularly in 3 common scenarios, can help ensure an accurate Dx.
VIDEO shows scabies mite in motion
PRACTICE RECOMMENDATIONS
› Consider scabies with any severe pruritic eruption. Conduct a thorough physical exam, preferably with a dermatoscope, for burrows in the webs and sides of fingers, proximal palm, and wrists. A
› Consider scabies in all patients—especially the immunocompromised—who have distal white or yellow thick, scaly, or crusted plaques. C
› Include scabies in the differential when patients present with smooth nodules of the genitals or pruritic smooth papules and plaques in other locations. A
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
3 diagnostic missteps to avoid
Misdiagnosis is often due to an overreliance on the clinical history without performing an adequate physical exam. In such cases, the physician often diagnoses a form of dermatitis as the cause of pruritic rash. (Admittedly, diagnostic error can result in either false-positive or false-negative findings, and many patients are diagnosed with scabies when they have dermatitis.)
A second misstep? Scabies may be overlooked in a patient whose lesions are nonpruritic, such as someone with an immunocompromising condition.
And finally, crusted scabies is frequently mistaken for psoriasis or chronic dermatitis.8
Diagnostic errors are exceedingly troublesome for patients and caregivers. It is not unusual for a hospital or long-term care facility to lose significant employee work hours due to a scabies epidemic or fear of a scabies epidemic. In a 2003 outbreak of scabies in a Canadian long-term care facility, an estimated $200,000 was needed to control disease spread.23
A topical agent is a mainstay of treatment
Permethrin cream is usually the first-line treatment choice.24 Ivermectin, topical (cream) or systemic (pill), is the commonly used alternative for patients who do not respond to, or cannot tolerate, permethrin cream. A recent meta-analysis examined the effectiveness of 5% permethrin cream, 1% ivermectin cream, and oral ivermectin (200 mcg/kg single or double dose).24 Overall, findings suggested there was no difference in the efficacy or in adverse effects of permethrin cream compared with ivermectin (topical or systemic) among adults. One study reported that permethrin cream was slightly more effective than ivermectin (cream or oral) because of the more rapid treatment response (approximately 94% clearance within 2 weeks of treatment, compared with 90%).25
Continue to: Adjust treatment for special populations
