What are the diagnostic and treatment approaches for scabies?

From the Guidelines

Scabies is diagnosed through clinical examination and microscopic identification of mites, eggs, or feces from skin scrapings, and the primary treatment is permethrin 5% cream, applied from neck to toes and left on for 8-14 hours before washing off, with a second application one week later. The diagnosis of scabies involves a combination of clinical presentation and laboratory confirmation, with the latter typically involving skin scrapings examined under a microscope for the presence of mites, eggs, or feces 1.

Diagnostic Approaches

• Clinical examination for characteristic skin lesions and burrows
• Microscopic identification of mites, eggs, or feces from skin scrapings
• Consideration of patient history and symptoms, such as intense itching, especially at night

Treatment Approaches

• Permethrin 5% cream is the primary treatment, applied from neck to toes and left on for 8-14 hours before washing off, with a second application one week later 1
• Alternative treatments include ivermectin (oral dosing at 200 μg/kg, repeated after 1-2 weeks), benzyl benzoate 25% lotion, or crotamiton 10% cream
• All household members and close contacts should be treated simultaneously to prevent reinfestation, even if asymptomatic 1
• Bedding and clothing should be washed in hot water and dried on high heat or sealed in plastic bags for at least 72 hours to kill mites 1
• Antihistamines or topical steroids may help manage itching, which can persist for 2-4 weeks after successful treatment due to hypersensitivity to dead mites

Special Considerations

• Crusted (Norwegian) scabies, a severe variant in immunocompromised patients, requires more aggressive treatment, often combining topical and oral medications under medical supervision 1
• Patients with HIV infection or other immunosuppressive conditions are at increased risk for Norwegian scabies and should be managed in consultation with an expert 1

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Adults and children Thoroughly massage Permethrin Cream, 5% into the skin from the head to the soles of the feet. Scabies rarely infests the scalp of adults, although the hairline, neck, temple, and forehead may be infested in infants and geriatric patients. In Scabies: Thoroughly massage into the skin of the whole body, from the chin down, paying particular attention to all folds and creases. A second application is advisable 24 hours later. INDICATIONS AND USAGE: For eradication of scabies ( Sarcoptes scabiei) and for symptomatic treatment of pruritic skin.

Diagnostic Approaches for Scabies:

• The provided drug labels do not directly address diagnostic approaches for scabies. Treatment Approaches for Scabies:
• Permethrin (TOP): Apply 5% cream from head to soles of feet, leaving it on for 8 to 14 hours before washing off. One application is generally curative 2.
• Crotamiton (TOP): Apply lotion to the whole body from the chin down, paying attention to folds and creases, with a second application advised 24 hours later 3.
• Indications and Usage: Crotamiton is used for the eradication of scabies and symptomatic treatment of pruritic skin 3. Key Considerations:
• Patients may experience persistent pruritus after treatment, which is rarely a sign of treatment failure 2.
• Demonstrable living mites after 14 days indicate that retreatment is necessary 2.

From the Research

Diagnostic Approaches for Scabies

• The diagnosis of scabies can be made through a combination of clinical findings, laboratory tests, and patient history 4.
• A laboratory diagnosis of scabies can be made by scraping the skin and examining the sample under a microscope for the presence of the scabies mite or its eggs 4.
• The diagnosis of scabies should be based on the following criteria:
  • Objective skin findings
  • Laboratory proof of the causative agent of infestation
  • Subjective feelings of the patient (itching at the typical time)
  • Positive epidemiological anamnesis (occurrence of clinical symptoms in several members of a family or group)
  • Diminishing of clinical symptoms after specific treatment with an anti-scabies medicament 4

Treatment Approaches for Scabies

• Topical permethrin is considered the most effective treatment for classic scabies 5.
• Oral ivermectin is also an effective treatment for scabies, although it may not be as effective as topical permethrin 5.
• Other treatment options for scabies include topical lindane, crotamiton, benzyl benzoate, sulfur, and natural synergized pyrethrins 5.
• The efficacy of different treatment options can vary, with some studies showing that permethrin has a faster onset of action than other treatments 6, 7.
• The cure rate for scabies treatment can range from 63.1% to 100%, depending on the treatment used and the follow-up time 6, 8, 7.

Comparison of Treatment Options

• A study comparing topical ivermectin and permethrin 2.5% cream found that both treatments were effective, with cure rates of 84.2% and 89.5%, respectively, at the 4-week follow-up 8.
• Another study comparing permethrin, crotamiton, and sulfur ointment found that permethrin had a faster onset of action and a higher cure rate at the 2-week follow-up, but all three treatments were equally efficacious at the 4-week follow-up 7.
• A study comparing single and double dose regimens of oral ivermectin and topical permethrin found that all three treatment modalities were equally efficacious, with cure rates ranging from 89.7% to 94.7% at the 4-week follow-up 6.