Simplified Diagnostic Approach to Scabies May Detect Most Cases

By Marilynn Larkin

January 04, 2019

NEW YORK (Reuters Health) - Examining a patient's hands, feet and lower legs - instead of the full body - may be sufficient to diagnosis about 90% of all scabies cases, researchers suggest.

Currently, a diagnosis of scabies relies mainly on a time-consuming examination of all accessible parts of the skin. However, "with the recent recognition of scabies as a neglected tropical disease by the World Health Organization, there is a need for standardized approaches to disease mapping to define populations likely to benefit from intervention, and to measure the impact of interventions," note Dr. Michael Marks of the London School of Hygiene and Tropical Medicine in the UK and colleagues.

Dr. Marks and colleagues analyzed data from three population-based surveys, including 1,373 people diagnosed with scabies, who made up about 25% of the combined sample. Participants had a median age of 14 and about half were female.

Scabies was mild in about half of participants, moderate in about one-third, and severe in the rest. Impetigo was significantly higher among those with scabies versus those without (odds ratio, 3.24).

Individuals were classified as having scabies or not, overall, based on a whole body assessment, and also in each of nine body regions. Body regions were defined as "exposed" if they could be routinely examined without removing clothes. This included the face; upper arm, including the elbow; lower arm, including the wrist; hands; lower leg, including the ankles; and feet.

"Unexposed" regions included the torso; upper legs, including the knee; and buttocks/groin (examined if patients had itching in those areas).

As reported online December 27 in PLoS Neglected Tropical Diseases, body regions with highest yield were the hands (sensitivity compared to whole body examination, 51.2%), feet (49.7%) and lower legs (48.3%).

Clinical examination of the exposed components of both limbs yielded a sensitivity of 93.2% across sex and age subgroups, regardless of scabies severity or the presence or absence of secondary impetigo.

Further, excluding the upper arms from the examination significantly reduced the sensitivity in a number of subgroups, whereas examining the remaining exposed site, the face, did not significantly increase sensitivity.

Dr. Marks said by email, "The study fits alongside the recently published International Alliance for the Control of Scabies Consensus criteria for the diagnosis of Scabies." (http://bit.ly/2VqXRz9)

"The current work is retrospective, but we are working to collect prospective data to validate both the Delphi criteria and the limited examination strategy and to develop a standardized training package that can be rolled out for nurses and clinical staff in any country," he told Reuters Health.

"Once validated, we believe the limited examination strategy will make it quicker and easier for ministries of health to assess if scabies is a significant problem," he concluded.

Coauthor Dr. Daniel Engelman of the University of Melbourne noted in a separate email to Reuters Health, "These findings apply everywhere. In developed countries, the need for limited protocols may not be as pressing, as access to dermatologists and physicians who can undertake a detailed examination is simpler."

"Further research is needed to assess these examination procedures," he added. "Several studies are currently underway or planned."

Dr. Adam Friedman, Director of Translational Research in the Department of Dermatology at George Washington School of Medicine and Health Sciences in Washington, DC, commented, "Scabies can present very differently in children, elderly, immunosuppressed and bed-bound patients. It can be quite protean in nature and therefore disregarding the gold standard of diagnosis, which is a mineral oil prep, is in my opinion inappropriate."

"A mineral oil prep is a simple bedside diagnostic tool," he told Reuters Health by email. "A physician dips a scalpel blade in mineral oil and lightly scrapes involved and highly suspicious skin. The debris on the blade is then wiped on a slide and the mite, and/or feces, and/or eggs can be visualized with light microscopy."

"Work is currently being performed to use dermoscopy to identify scabies, as well," he noted.

"The current study offers a way to look at higher risk locations and increase suspicion," he said. "However, it is based solely on clinical diagnoses, not the gold standard."

"The treatments for scabies are relatively benign, so treating empirically is not a bad idea if suspicion is high. However," he concluded, "training physicians on mineral oil preps is easy and would be much more effective."

SOURCE: http://bit.ly/2VqfOhu

PLoS Negl Trop Dis 2018.

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