Coronavirus: dermatology update
In response to the coronavirus (COVID-19) outbreak, please read our advice and information before attending the service.
Our mycology laboratory is involved in the study of fungi causing human disease. Diagnosis involves microscopic examination of infected tissue and culture to identify the disease-causing fungi. Accurate diagnosis enables the clinician to prescribe appropriate antifungal treatment.
Dermatological infections include:
- athlete’s foot
- tinea capitis (scalp hair loss)
- pityriasis versicolor
- onychomycosis (finger and toe nail infection).
We are experts in the diagnosis of fungal infections (mould and yeast), erythrasma and pitted keratolysis.
We aim to promote accurate diagnosis of fungal infections and to actively participate in the education of mycotic diseases. The unit teaches and trains students and healthcare professionals, and participates in and organises national courses on medical mycology.
Please send all specimens to the address at the top of this webpage along with a referral letter or a completed mycology form.
Specimens are accepted from any GP, consultant, private clinician or health practitioner.
If a specimen is urgent, please notify us and ensure all contact information is provided.
We are happy to answer queries concerning sampling, results, or treatment, and to provide information and advice to clinical colleagues. However, where the patient concerned has a complicated medical history the enquiry will be forwarded to a dermatologist for specialist advice on treatment.
Up to three separate specimens per patient are accepted for one charge, for example sole, toe web and toe nail. Microscopy results are issued within two working days of receipt, and culture results are three to four weeks later.
Ideally there should be enough skin / nail / hair to cover a five pence coin. If it is difficult to obtain sufficient scrapings please swab the area and send that as well. The swab can be used for culture and the scrapings for microscopy.
Please contact the laboratory to discuss tests required and charges.
We aim to report microscopy results within two working days of receipt, and culture results three to four weeks later.
Results will only be sent to the requesting practitioner, not reported to the patient.
Patients attending clinics at St Thomas' can be examined in the mycology laboratory 9am-5pm, Monday-Friday.
Private patients and patients from local GP surgeries can attend the mycology laboratory facilities 9.30am-4.30pm, Monday-Friday.
At St Thomas’, staff will attend the bedside of any immobile inpatient requiring mycological testing, on condition that the requesting clinician has first contacted the laboratory to discuss the patient’s condition, availability, and can provide a request form or letter.
We run one of the largest direct access postal diagnostic services for superficial mycoses in the country.
Our highly experienced staff process approximately 10,000 postal specimens and examine and sample up to 350 patients per year. Postal specimens are accepted from clinicians referring private or NHS work. We will process up to three specimens per patient. Direct microscopy is performed using both Calcofluor white fluorescence and bright-field microscopy and results are issued within two working days of receipt of the specimen. Culture for dermatophytes have a three to four week turnover from date of receipt.
Information needed for laboratory diagnosis of superficial infections
The processing and interpretation of laboratory tests are influenced by the amount of patient information provided and the quality and quantity of the material submitted.
- First name and surname, sex, date of birth, ethnic origin and reference number for the patient are standard requirements.
- A history of residence overseas, recent travel, and contact with animals may be relevant.
- If a specific mycosis is suspected please indicate this on the form, for example pityriasis versicolor or candidosis.
- Please indicate exact sample site for skin (for example hand, leg) and whether it is a toe or finger nail.
- Any samples that are not labelled with patient identifiers, or accompanied by a completed request form may not be processed. If the laboratory cannot match the sample to a request form and sender, the sample will be rejected and not processed.
Transportation of samples to the laboratory
All samples of skin, hair and nail should be submitted in a piece of folded paper, or a packet, secured with a paper clip. This keeps the specimen dry and free from contamination. Any paper will suffice, although coloured paper contrasts well against skin and hair making it easier to see the specimen.
If sending a liquid sample or a biopsy, please contact the laboratory first as delays in delivery to the laboratory can compromise test results. These samples should be received ideally the same day or within 48 hours.
All samples should be sent to the laboratory on the day they are taken. If there are significant delays in receipt the laboratory will note the delay on the test report, and for biopsies may contact the doctor to discuss the reliability of the test, and whether it should proceed.
Please do not send:
- specimens in glass as this breaks and is a hazard to laboratory staff, unless using a specialised glass slide holder
- specimens in plastic containers as the electrostatic forces make it very difficult to remove skin scales.
For more information on transportation of specimens visit the Viapath website.
If cultures are to be sent to the laboratory please refer to the Viapath website for transportation instructions. All cultures should be category B hazards. Please contact the laboratory prior to sending the sample.
Collecting samples from skin
Skin scrapings will give the best results and allow reliable direct examination.
If the lesion has an active edge this is the best site for scraping, otherwise a general scrape of the scaly area is suitable. (Use the blunt edge of a scalpel blade, or a glass slide, to scrape the lesion, but do not send the blade or slide to the laboratory as they pose a hazard).
For intertriginous lesions in the groins etc., and for mucous membrane sites, transport swabs are good for culture of Candida spp., but even in dermatophyte infections if it is difficult to obtain adequate material a transport swab can be used for culture.
For the diagnosis of pityriasis versicolor a sellotape strip may be taken and placed face down on a glass slide which must be sent in a proper slide holder to the laboratory.
For blistering lesions the roof of the blister is the best material for direct examination and culture.
A sample to cover a 5 pence coin is more than adequate for all tests. Collect only affected looking tissue.
Collecting samples from hair
Not only scalp, but vellus hairs may be infected by fungi. The root end of the infected hair is the best material for direct examination; cut hairs are of no value.
In other infections diseased hairs may be much shorter and a scrape of the lesion may produce scales with infected hairs embedded in them as tiny dark stumps, showing up as black dots.
Generally we would recommend scraping rather than plucking. For culture, disposable unpasted toothbrushes (available commercially) brushed at least ten times through the hair are a very sensitive method of sampling the scalp and may also be used in epidemiological studies and for sampling pets.
In cases of scalp kerion, which may be very inflamed and painful, a transport swab may again give a positive culture. If a child has scalp ringworm it is recommended that all the other children in the family should be screened with a brush sample, regardless of whether they show obvious clinical signs; subclinical infections are common with some dermatophyte species.
Collecting samples from nails
Using nail clippers, samples should be taken comprising the whole thickness of the nail, as near as possible to the proximal edge of the lesion. The majority of infections start under the nail, so the subungual debris is particularly valuable. This can be removed with a scalpel or dental probe. Superficial scrapings of the nail plate are only useful in cases of superficial onychomycosis, where white crumbly patches are seen on the dorsal surface of the nail or in proximal subungual onychomycosis.
Up to 50% of nails in which fungus has been seen on direct microscopy fail to grow a pathogen. Therefore if skin lesions are present in soles, toe webs or on palms please send samples from these as well, as they are probably caused by the same pathogen and are more likely to give a positive culture.
If paronychia is present use a transport swab for culture.
Disposal of sampling equipment
Dispose of all sharps according to local policies, usually in a sharps bins such as the type used for needles. Any materials or containers contaminated with patient tissue should be disposed of in a clinical waste container.
Sources of sampling equipment
The specimen transportation packs that we use are called Mycotrans and they have a blue coloured insert and are obtained from:
P O Box 1172
Scotland, ML12 6NN.
Tel/fax: 01899 830555
The brushes we use are disposable toothbrushes and unpasted. They are obtained from:
Whiteley’s office Supplies Ltd
Kent, BR1 4DR
Tel: 020 8313 3344