Section 5.0 Patch Testing

Patch testing services and implementation in Australia

It is essential that people with suspected dermatitis are patch tested comprehensively; this potentially identifies the causes of dermatitis, which can then be eliminated. Patch testing can be a time consuming, expensive and complex service to establish. It is time consuming for the dermatologist, and for nursing staff with patch preparation and product dilution. It is also expensive from the resource perspective with patches and allergens. With all this ‘expense’ in mind it would be easy to disregard the importance of patch testing. However, there are cheaper ways for patch testing services to be offered. The type of patch testing service utilised will depend on nursing staff and time, frequency and demand of patch testing, geographical location as well as the skill and knowledge level of the patch tester. Available patch testing options are discussed below.

In the past there have been two main methods of patch testing primarily used.

The first method involves stocking a range of commercially available allergens, of which there are more than 400 available for purchase.

Commercially available allergens


Chemotechnique allergens
 
allergEAZE® allergens

Buying a large assortment of individual allergen syringes can be costly, with each syringe often costing between than $35 and $90, and each having an expiry date of approximately 1.5 to 2 years (however some are shorter than this).

Allergens kept too long past their use-by date risk changes occurring to their chemical makeup, which means reliability of the patch test reactions is limited. In addition, patients are also able to bring their own samples from work and home for testing. In this situation the dermatologists decide what to test the individual to, according to their history. Allergens are applied to the tapes, which are then placed on the patient’s back for two days. The patient is reviewed after a further two to four days, when a final interpretation (or reading) of the reactions is made.

The second method of patch testing involves a pre-packaged patch test system (True-Test®), which is simpler to apply but still relatively expensive (when compared to CABA), despite there being significantly less allergens available for testing (with only 24 allergens are available). Sometimes these are used as a screening test by the dermatologist and some allergists. These tests are standardized, so there is no option for selecting alternative individual allergens. If the results are negative, but allergic contact dermatitis is strongly suspected on clinical grounds, then more extensive testing is indicated. There is evidence that suggests using these pre-prepared standardized tests correctly identifies allergens in only 28% of patients9. The cost of True-Test® can be found https://www.smartpractice.com/shop/category?cn=T.R.U.E.-TEST%C2%AE-Ready-to-Use-Patch-Test-Panels&id=508222&m=SPA.

Contact Allergen Bank Australia (CABA) was established by the Skin Health Institute, Melbourne as a mail order patch test service. It aims to assist dermatologists provide comprehensive patch testing without having to purchase and prepare an exhaustive set of allergens in their rooms. Dermatologists have access to more than 400 allergens via this service. CABA involves patient specific allergens being mailed to the dermatologist, following the lodge of an order via the website www.patchcams.asn.au or by fax, phone or email. This service is detailed in Section 5.1 of this manual.

Setting up a Patch Testing Service

Generally, patch testing occurs over 3 appointments over the course of a week. At the Skin Health Institute, Melbourne the first appointment is on Monday, the second appointment on Wednesday and the third appointment being Friday. Day 7 appointments are performed by some clinics, because it is suggested that more allergic reactions are detected with this later reading.

Some centres prefer to test over 4 appointments, where patients are initially assessed in a separate clinic, and then return on a separate occasion for the actual patch testing to commence, which may be a week, several weeks or months following the initial appointment. Each centre or clinic is different and will depend in the availability of the dermatologist.

Referrals are primarily received from dermatologists. However, in some clinics, such as the Occupational Dermatology Clinic in Melbourne, referrals are also accepted from GP’s and workplaces or staff health clinics. Add in link for referral

When setting up a new Patch Testing clinic you will need to decide what method of allergen supply will be used, such as a full supply of allergens, True Test or use of CABA. If sourcing individual allergens and series, there are a couple suppliers which are listed below. These companies have hundreds of allergens available, many different series as well as resources and information sheets.

When ordering allergens it is possible to have a mixture of allergens from both allergen suppliers as they often stock different concentrations/strength of allergens. There are more than 400 different allergens are commercially available.

Both companies have also created an “Australian Baseline Series” or an ‘ABS’ as it is commonly referred to. This series includes the 60 most common allergens that are relevant to the Australian setting, and was composed after much experience and data collection by Associate Professor Rosemary Nixon, Dr Bruce Tate, Dr Mei Tam, Dr Adriene Lee and Dr Jennifer Cahill at the Skin Health Institute, Melbourne. The series from each company are slightly different due to different allergens or allergen concentration that they have available.

In addition to allergens, another essential item for patch testing is a computer program that will assist with allergen and clinic management. At the Skin Health Institute, Melbourne a program called PatchCams© has been developed over many years and is used in all patch testing clinics. See Section 5.2 for details about this program.

Products needed to perform patch testing

There are several key items that are needed when making up the patches. At SHI Melbourne, we suggest using:

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  • Patches
  • Mixing cups
  • Wooden sticks
  • Syringes
  • Forceps
  • Scissors and blades
  • Gauze

Skin markers are also needed to mark the location of the patches. Two examples of commercially available skin markers are shown below.

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Example of when a skin marker is used:

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A skin marker is used to mark the location of each disc. This is done when patches are first applied and then again when patches are removed. If a patient is having readings performed at day 7, it may be necessary to ask the patient to reapply/go over the top of the existing lines, to ensure they are still visible on day 7. A cheap, disposable skin marker could be sent home with the patient.

Patch varieties available

There are two primary brands of patch testing products in Australia, allergEAZE® and Chemotechnique Diagnostics. Each company has a few different types of patch testing chambers or ‘patches’ available. Deciding which product to use is up to your organisation to decide, depending on patient or cost/budget related factors. There are fabric styles and also the newer style waterproof patch.

Selection of the patch will also probably be determined by how many patients are being tested at the one time. For example at the Skin Health Institute, Melbourne up to 16 patients can be patch tested in the one clinic. So the ABS series is made for each patient before they arrive at the clinic, so the patient does not choose which patch type they would like to be tested with. However, if you were only going to be testing one patient a day or week, and only make the tests up when they arrive, then it may be more possible for the nurse or doctor to decide on the best patch type to be used. Or alternatively you could make ahead of time and store them in transport containers or use the IQ Ultra patches which include a lid for each packet.

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Informed consent and patch testing

Consent from the patient is required before patch testing is performed. At the Skin Health Institute, Melbourne all patients are given an in-depth information sheet and consent form before seeing the doctors, and before any patches are applied. This consent form describes the patch testing process and any potential risks and side-effects of the patch tests. The consent form is checked before any patches are applied to the patient. At Skin Health Institute, Melbourne, patients also need to consent to their information being entered into the electronic notes system called PatchCams®. Information is collected in accordance with privacy (Commonwealth Privacy Act 1988, The Health Records Act 2001 and Information Privacy Act 2000). See attachment ? for a copy of our consent form.

A consent form for prick testing is also available. See attachment ?

Medicare and costs and ethical consideration

Patch testing can be expensive. Costs of patch tests vary from centre to centre and also depend on what type of patch testing is used, such as full comprehensive tests, T.R.U.E Test® or even the Contact Allergen Bank Australia service. The cost is also dependant on how many patches are applied. When traditional patch testing is used, normally a minimum of 6 patches or 60 allergens are tested, as there are 60 allergens in the Australian Baseline series.

Patch testing attracts a rebate under Medicare. The Item numbers used for patch testing are:

104 Initial consultation

12012 < 26 allergens

12017 26-50 allergens

12021 51-75 allergens

12022 76-100 allergens

12024 100 plus allergens

105 Review appointment – patches off and final appointment

(Current Feb 2022)

Patients are generally charged an initial consultation fee (104) on day 1. This consultation takes longer than a standard dermatology consultation because an extensive history of skin exposures is ascertained. Thirty minutes is scheduled at the Skin Health Institute, Melbourne. They are then charged an item number for the cost and preparation of patch tests, as listed above.

On the second and final appointment, patients are charged for review consultations (105). At the second appointment, if the patient has developed some reactions, additional enquiries may be directed to the workplace or to manufacturers of skin care products, or additional tests may be applied to clarify the positive reactions. The final consultation is often quite long, as it involves making a final diagnosis of the patient’s skin condition and explaining this to the patient, as well as advice about treatment and management.

True Tests are cheaper, but less comprehensive. The limitations with these tests have been mentioned on page.

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