Goal: To demonstrate evidence of mites (adults, nymphs, eggs, feces)
Preferred lesions to sample:
(1) papule
(2) burrow
Lesions unlikely to be positive (Woodley and Saurat):
(1) vesicles
(2) excoriations
Preferred sites to examine:
(1) between the fingers
(2) at the wrist, especially the medial side of the hypothenar area
(3) underneath fingernails
Burrow Ink Test (BIT):
(1) Blue or black ink is rubbed onto a papule.
(2) The ink is then immediately wiped off with an alcohol pad to remove the surface ink.
(3) The test is positive if it tracks down a mite burrow, resulting in zig-zag line in the skin.
Needle (digging):
(1) A needle is used to probe into the head of a burrow.
(2) Dislodged material is transferred to a slide.
Skin Scraping:
(1) A burrow is identified and covered with mineral oil.
(2) The edge of a slide (or a scalpel blade if held correctly by an expert) is rubbed back and forth over the burrow. This has to be done with some force (but not too much). A small amount of blood is often present.
(3) The mineral oil is scraped up and placed on a slide under a coverslip.
Superficial shave biopsy over a burrow (Martin and Wheeler):
(1) The end of a burrow is elevated between the thumb and forefinger or between forceps, then carefully shaved off by a sharp scalpel blade. The material is placed on a slide for examination.
(2) It is potentially more invasive than other methods.
A single negative examination does not exclude the diagnosis, especially if:
(1) the number of lesions are small
(2) the testing is done by a novice
(3) the site selected is suboptimal.
