A community-based validation of the International Alliance for the Control of Scabies Consensus Criteria by expert and non-expert examiners in Liberia.

• Published in: PLOS Neglected Tropical Diseases
• Main Authors: Stephen L Walker, Shelui Collinson, Joseph Timothy, Samuel K Zayzay, Karsor K Kollie, Neima Candy, Eglantine Lebas, Katherine Halliday, Rachel Pullan, Mosoka Fallah, Michael Marks
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2020
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270; Arctic; Burrows
• Online Access: https://doi.org/10.1371/journal.pntd.0008717; https://doaj.org/article/42827040137949a19b1c1056e8945cfc

Background The International Alliance for the Control of Scabies (IACS) recently published expert consensus criteria for scabies diagnosis. Formal validation of these criteria is needed to guide implementation. We conducted a study to provide detailed description of the morphology and distribution of scabies lesions as assessed by dermatologists and validate the IACS criteria for diagnosis by both expert and non-expert examiners. Methods Participants from a community in Monrovia, Liberia, were independently assessed by two dermatologists and six non-expert examiners. Lesion morphology and distribution were documented based on the dermatologist examination. Diagnoses were classified by IACS criteria and the sensitivity and specificity of non-expert examiner assessments calculated. Results Papules were the most common lesions (97.8%). Burrows were found in just under half (46.7%) and dermatoscopy was positive in a minority (13.3%). Scabies lesions were found in all body regions but more than 90% of patients could have been diagnosed by an examination of only the limbs. Severity of itch was associated with lesion number (p = 0.003). The sensitivity of non-expert examiners to detect typical scabies ranged between 69-83% and specificity 70-96%. The sensitivity of non-expert examiners was higher in more extensive disease (78-94%). Conclusions The IACS criteria proved a valid tool for scabies diagnosis. For the purposes of implementation papules and burrows represent truly 'typical' scabies lesions. Non-expert examiners are able to diagnose scabies with a high degree of accuracy, demonstrating they could form a key component in population-level control strategies.