From the Guidelines
Scabies diagnosis is primarily based on clinical examination and history, with confirmation through microscopic identification of the mite, eggs, or feces, as the most recent and relevant evidence from 1 suggests that scabies in adults is frequently sexually acquired and presents with pruritus as the predominant symptom. The diagnosis of scabies involves recognizing characteristic symptoms such as:
- Intense itching, especially at night
- A rash with small red bumps or blisters
- Visible burrows on the skin, typically found between fingers, on wrists, elbows, armpits, waistline, buttocks, and genital areas To confirm the diagnosis, a skin scraping can be taken from a suspected burrow and examined under a microscope to identify the Sarcoptes scabiei mite or its eggs, as noted in 1. Alternatively, a dermatoscope may be used to visualize the mites directly on the skin. In some cases, diagnosis is made based solely on clinical presentation and history, especially when there are multiple family members with similar symptoms, highlighting the importance of considering the patient's context and potential for contagion, as mentioned in 1. It's essential to note that itching may persist for several weeks after successful treatment due to a hypersensitivity reaction to the dead mites, emphasizing the need for thorough follow-up and patient education. Early diagnosis is crucial to prevent spread to close contacts, as scabies is highly contagious through prolonged skin-to-skin contact, underscoring the importance of prompt and accurate diagnosis, as indicated by the evidence from 1.
From the Research
Scabies Diagnosis
- Scabies is a common, highly pruritic infestation of the skin caused by Sarcoptes scabiei var. Hominis, characterized by intense nocturnal pruritus and specific lesions such as burrows, papules, vesicles, and excoriations 2.
- The typical areas of the body affected by scabies include finger webs, wrists, axillary folds, abdomen, buttocks, inframammary folds, and, in men, the genitalia 2.
- Definitive diagnosis is made when the scabies mites or their eggs or fecal pellets can be identified on a light microscope, with new techniques for diagnosis including the use of epiluminiscence microscopy 2.
- Clinical examination remains the mainstay of diagnosis, although dermatoscopy is a useful adjunct, presenting with severe itch and a papular rash, with a predilection for the hands, feet, and genitalia 3.
Diagnostic Considerations
- Scabies should be on the differential for any patient who presents with a pruritic dermatosis, considering a wide range of diagnostic possibilities to avoid over- or underdiagnosis 4.
- Atypical or complex presentations may necessitate the use of more definitive diagnostic modalities, such as microscopic examination of KOH prepared skin scrapings, high-resolution digital photography, dermoscopy, or biopsy 4.
- Thread-like papules (burrows), new, intense pruritus, and dermatitis guide the suspected diagnosis, which is confirmed by the microscopic or dermatoscopic demonstration of scabies mites 5.
Diagnostic Challenges
- Treatment failures can occur due to improper application of external agents, failure of repeated treatment with ivermectin, incomplete decontamination of furnishings and clothes, failure to simultaneously treat contact persons, and the patient's belonging to a risk group 5.
- There is a rising number of well-documented cases of poor response to permethrin, although there is no direct proof of resistance of scabies mites to permethrin 5.