A novel clinical grading scale to guide the management of crusted scabies

PLoS Negl Trop Dis. 2013 Sep 12;7(9):e2387. doi: 10.1371/journal.pntd.0002387. eCollection 2013.


Background: Crusted scabies, or hyperinfestation with Sarcoptes scabiei, occurs in people with an inadequate immune response to the mite. In recent decades, data have emerged suggesting that treatment of crusted scabies with oral ivermectin combined with topical agents leads to lower mortality, but there are no generally accepted tools for describing disease severity. Here, we describe a clinical grading scale for crusted scabies and its utility in real world practice.

Methodology/principal findings: In 2002, Royal Darwin Hospital (RDH), a hospital in tropical Australia developed and began using a clinical grading scale to guide the treatment of crusted scabies. We conducted a retrospective observational study including all episodes of admission to RDH for crusted scabies during the period October 2002-December 2010 inclusive. Patients who were managed according to the grading scale were compared with those in whom the scale was not used at the time of admission but was calculated retrospectively. There were 49 admissions in 30 patients during the study period, of which 49 (100%) were in Indigenous Australians, 29 (59%) were male and the median age was 44.1 years. According to the grading scale, 8 (16%) episodes were mild, 24 (49%) were moderate, and 17 (35%) were severe. Readmission within the study period was significantly more likely with increasing disease severity, with an odds ratio (95% CI) of 12.8 (1.3-130) for severe disease compared with mild. The patients managed according to the grading scale (29 episodes) did not differ from those who were not (20 episodes), but they received fewer doses of ivermectin and had a shorter length of stay (11 vs. 16 days, p = 0.02). Despite this the outcomes were no different, with no deaths in either group and a similar readmission rate.

Conclusions/significance: Our grading scale is a useful tool for the assessment and management of crusted scabies.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Antiparasitic Agents / therapeutic use
  • Australia
  • Clinical Medicine / methods*
  • Female
  • Hospitalization
  • Humans
  • Ivermectin / therapeutic use
  • Length of Stay
  • Male
  • Middle Aged
  • Sarcoptes scabiei / growth & development*
  • Scabies / diagnosis*
  • Scabies / drug therapy
  • Scabies / pathology*
  • Severity of Illness Index*
  • Treatment Outcome


  • Antiparasitic Agents
  • Ivermectin

Grant support

This work was assisted by salary support from the National Health and Medical Research Council of Australia (Early career fellowships to JSD and SYCT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.