The diagnosis of scabies is usually made clinically, as although laboratory testing can be performed by taking scrapings from the suspicious looking area of skin, this has very poor sensitivity.
Like other regions in New Zealand, the positivity rate for scabies laboratory examination is very low in Canterbury, at < 10% of all collections. This can be due to multiple factors, including experience of the examiner, pre-treatment of the patient, absence of scabies on the patient or too few mites on a patient making them difficult to find.
As such, from Monday 10th February 2020, skin scrapings for Scabies will only be performed following a discussion of the primary care doctor with a clinical microbiologist. If the clinical microbiologist supports a scraping please note the name of the microbiologist on the request form and ask the patient to make an appointment with the laboratory.
Where there is no evidence of a discussion with a clinical microbiologist included on the request form the on call clinical microbiologist will review the request form and makes a decision regarding processing.
Health Pathways contains information regarding diagnosis and testing which are included below.
- Diagnosis is usually clinical. See DermNet NZ – Scabies for useful images
- Testing on skin scrapings has poor sensitivity
Refer for testing, as below, recognising low sensitivity, if:
- unclear diagnosis
- failed appropriate treatment. If possible, refer at least 2 weeks after last scabies
- treatment attempt
- possible infestation in vulnerable community, e.g. rest home
For any queries, please contact:
- Dr Joshua Freeman
- Clinical Director, Microbiology
- Canterbury Health Laboratories
- Dr Arlo Upton
- Clinical Microbiologist
- Canterbury SCL