Scabies is a skin infestation caused by the microscopic mite Sarcoptes scabiei, which burrows into the skin and lays eggs. It causes intense itching and a rash. Due to symptom similarities with other skin conditions, accurate diagnosis by a healthcare professional is important. This article details the official diagnostic process.
Initial Doctor Assessment
A healthcare professional’s assessment for suspected scabies begins with a thorough visual examination of the skin. They look for characteristic rashes, burrows, and lesions, often appearing as tiny, raised, skin-colored lines or bumps. Common affected areas include the webbing between fingers, wrists, elbows, armpits, waist, buttocks, or genitals. In infants and young children, the rash may also appear on the face, scalp, palms, and soles of the feet.
The doctor will also gather a comprehensive patient history, inquiring about symptoms like intense itching, especially if it worsens at night, and its duration. They will also ask if other household members or close contacts are experiencing similar symptoms, as scabies is highly contagious through direct skin-to-skin contact. This evaluation helps guide further diagnostic steps.
Laboratory Diagnostic Procedures
To confirm a scabies infestation, healthcare providers employ specific laboratory diagnostic procedures. One common method is the skin scraping test. During this procedure, a small skin sample from a suspected burrow or affected area is gently scraped using a scalpel blade, often after applying mineral oil. This process is generally quick and causes minimal discomfort, with some practitioners noting it is painless. The mineral oil helps mites adhere to the sample and improves visibility under the microscope.
Another technique to identify burrows before scraping is the burrow ink test. Washable ink is applied over a suspected burrow and then wiped away with an alcohol swab. If a burrow is present, the ink penetrates and remains within the tunnel, making the characteristic wavy line more visible. This is useful for locating subtle burrows.
Once collected, the skin sample is placed on a glass slide and examined under a microscope. This microscopic examination allows for the identification of Sarcoptes scabiei mites, their eggs, or fecal matter (scybala). Finding any of these elements confirms an active infestation. Multiple scrapings from different sites may be taken to increase the chances of finding evidence of mites, especially since their number can be quite low.
Interpreting Your Test Results
If microscopic examination of skin scrapings reveals mites, eggs, or fecal matter, the diagnosis of scabies is confirmed. This positive result leads to a treatment plan, typically involving prescribed topical creams or oral medications.
A negative test result, however, does not always rule out scabies. Individuals with scabies often have only a small number of mites, making them difficult to locate during sampling. In such cases, a diagnosis can still be made based on clinical presentation, including the characteristic rash, intense itching, and similar symptoms in close contacts. The turnaround time for results can be immediate if the sample is examined on-site, or it may take a day or two if sent to an external laboratory.
Preparing for Your Visit and Next Steps
To facilitate an accurate diagnosis, avoid applying lotions, creams, or ointments to your skin before the appointment. These can interfere with visual examination and skin sample collection. Be ready to discuss your symptoms in detail, including their onset and any potential exposures.
If scabies is diagnosed, your doctor will discuss treatment options, typically including topical creams like permethrin or oral medications such as ivermectin. You will also receive guidance on treating close contacts and decontaminating your environment, such as washing bedding and clothing in hot water to kill mites and eggs. Should the diagnosis remain unclear after initial tests, your doctor may suggest further testing, re-evaluation, or explore alternative diagnoses.