Scabies: Refine your exam, avoid these diagnostic pitfalls

Handheld illumination with a dermatoscope will allow visualization of the mite ­(FIGURE 8). (See “How fast do scabies mites move? Dermoscopy video answers that question.”) Dermatoscope findings consistent with scabies include a “delta ­glider,” a dark triangular shape that is the mite’s head hidden in the burrow,²⁰ or the classic “jet with contrail” (FIGURE 8).²¹ Scrape the burrow to discover the mature scabies mite (FIGURE 9) and confirm the diagnosis.

^{COURTESY OF ROMAN BRONFENBRENER, MD}

Microscopic examination of scrapings has a reported sensitivity and specificity of up to 90% and 100%, respectively, when collection of scrapings is performed accurately and contains ova, feces, or mites.^14,20,22 Dermatologists increasingly use dermatoscopes to diagnose scabies. Dermoscopy's sensitivity is 91% and specificity is 85% to 86%,¹⁴ which is a reassuring frame of reference for physicians who do not routinely use dermatoscopes and instead rely on scrapings.

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