Dermatology tests include:
- Dermatoscopy for pigmented lesions, such as moles
- KOH examination for superficial fungal infections
- Microscopic examination for parasites (Scabies prep)
- Patch testing for contact allergy
- Skin biopsies for histopathologic evaluation, immunofluorescence, and microbiologic culture
- Tzanck smear for Herpes zoster
- Gram’s Staining for bacterial infections
Diagnostic tests are indicated when the cause of a skin lesion or disease is not obvious from history and physical examination alone.
One procedure is a punch biopsy, in which a tubular punch (diameter usually 4 mm) is inserted into deep dermal or subcutaneous tissue to obtain a specimen, which is snipped off at its base. More superficial lesions may be biopsied by shaving with a scalpel or razor blade. Bleeding is controlled by aluminum chloride solution or electrodesiccation; large incisions are closed by sutures. Larger or deeper biopsies can be done by excising a wedge of skin with a scalpel. Pigmented lesions are often excised for histologic evaluation of depth; if too superficial, definitive diagnosis may be impossible. Diagnosis and cure can often be achieved simultaneously for most small tumors by complete excision that includes a small border of normal skin.
We at COSMETIQUE prepare slides, do microscopy and take images, which are then sent to our collaboration lab in USA, Rao Dermatology Lab, for evaluation and final diagnosis.
Skin scrapings help diagnose fungal infections and scabies. For fungal infection, scale is taken from the border of the lesion and placed onto a microscope slide. Then a drop of 10 to 20% potassium hydroxide is added, followed by Swartz Lamkin staining. Hyphae, budding yeast, or both confirm the diagnosis of tinea or candidiasis. For scabies, scrapings are taken from suspected burrows and placed directly under a coverslip with mineral oil; findings of mites, feces, or eggs confirm the diagnosis.