Skin Prick Testing in the Diagnosis of Allergy - Guidelines for

Publication: 26/04/2017  
Next review: 20/04/2023  
Clinical Guideline
CURRENT 
ID: 4997 
Approved By: Trust Clinical Guidelines Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2020  

 

This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Guidelines for Skin Prick Testing in the Diagnosis of Allergy 

1. PURPOSE

Based on consultation with associated disciplines within the Trust, this guideline will ensure safe, uniform, evidence based technique for performing skin prick testing, recording and interpreting results. All patients will be assured of a quality approach to allergy diagnosis testing through implementation of this document.

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2. SCOPE

To identify suspected allergies in patients who have presented with a clinical history of allergy symptoms or to confirm results of blood testing. This procedure is to be followed in the Clinical Immunology Department based in Beckett Wing SJUH

The client group is essentially adults who have been identified as having possible allergy through clinical history assessment by a qualified medical practitioner.

Skin prick testing is used to:

i. Confirm the presence of Type I antibody-mediated (IgE) hypersensitivity to foreign substances suspected from clinical history, in both the inpatient and outpatient environment.

ii. Determine whether environmental allergens are responsible in difficult to manage cases of asthma, urticaria, eczema or anaphylaxis.

iii. Document immediate hypersensitivity prior to desensitisation therapy.

Contraindications.

i. Testing must not be performed if the patient is experiencing severe problems with eczema or dermatitis, at the test site.

ii. Documented anaphylactic reaction to allergen in previous testing conditions, recorded in the patient medical notes, or obtained from medical history.

iii. Known systemic reaction to allergen stabilisers or diluents.

iv. Use of antihistamine, or medication with antihistamine properties, 5 days or less prior to the test. Use of topical corticosteroids/antihistamines on the proposed test site in the previous 48 hours.

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3. BACKGROUND INFORMATION

Allergies to environmental allergens can involve almost every organ of the body. Although allergic rhinitis is the commonest, lower respiratory tract, conjunctiva, skin and the gastrointestinal tract are frequently affected. Accurate diagnosis of triggering or causative allergens is essential in order to give appropriate advice and treatment. Skin Prick Testing is performed on patients with suspected immediate-type hypersensitivity to one or more allergens. Puncture sites are then examined for a wheal and flare response that would indicate Type I antibody-mediated (IgE) hypersensitivity to the test allergen. When the allergen is introduced into the skin on a previously sensitised individual, IgE molecules on the surface of mast cells are bridged and degranulation of the mast cell occurs. Pre-formed granules containing histamine are released followed by infiltration of the dermis by eosinophils and neutrophils, which have been attracted, to the site by chemotactic factors. Testing in this way is a cheap, rapid and accurate way of identifying the causative allergens in an atopic individual. Properly used, positive skin tests help distinguish allergic rhinits from non-allergic causes such as vasomotor rhinits.

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4. PROCEDURE TO BE FOLLOWED

Contraindications.

Testing must not be performed if the patient is experiencing severe problems with eczema or dermatitis, at the test site.

Documented anaphylactic reaction to allergen in previous testing conditions, recorded in the patient medical notes, or obtained from medical history.

Known systemic reaction to allergen stabilisers or diluents.

Use of antihistamine, or medication with antihistamine properties, 5 days or less prior to the test. Use of topical corticosteroids/antihistamines on the proposed test site in the previous 48 hours.

Preparation.

i. Prior to testing the patient should undergo a complete medical history and physical examination by clinician, documented in medical notes. The procedure must be explained to the patient, who will then be given the opportunity to ask questions regarding the test, in order for the nurse or clinician to be able to gain verbal consent to the test from the patient or guardian.

ii. It is important to point out that the test will take 25-30 minutes in all to perform.

iii. Emergency resuscitation equipment and drugs, appropriate for adults to treat anaphylaxis, must be available.

iv. A trained nurse/health care assistant or clinician must perform Skin Prick Testing. A clinician would be required to be immediately available, within the department, for rare cases of anaphylaxis. Verbal consent for the procedure must be obtained prior to testing.

v. Check patient details to confirm correct patient.

vi. Check expiry dates and integrity of skin testing solutions.

Resources.

i. Allergens used for testing are available as standardised extracts, mostly stabilised in 50% glycerol. Allergens must be refrigerated between 2 and 8oc.

ii. Comfortable chair.

iii. Non-allergic tape for allergen marking.

iv. Sharps disposal container.

v. Pen

vi. Ruler or measuring tool.

vii. A supply of lancets is required, one for each allergen.

viii. Cotton Wool/Tissue.

ix. Availability of resuscitation equipment. Oral antihistamines.

x. Wheal/flare measuring template, or tape to outline size of response.

xi. Positive control: 10mg/ml histamine in 50% glycerol and 50% buffered saline.

xii. Negative control: 50% glycerol and 50% buffered saline.

xiii. Skin prick testing record chart.

Technique.

Following review and confirmation of test allergens to be used as prescribed by the clinician, a drop of each allergen is placed individually in a predetermined location on the skin (except in cases outlined in ‘Contraindications’).

i. Drops should be placed at least 3cm apart. The testing area must be 3cm below the cubital fossa and 5cm above the wrist, on the volar surface of the forearms or the skin of the back. Each allergen must be identified by coding on the skin in felt tip pen, or marker, which is provided by some pharmaceutical companies. There appears to be no evidence to indicate a maximum numbers of allergens that may be used.

ii. The drop must be pricked at right angles with a lancet, with light and constant pressure.

iii. The lancet must be removed straight upwards. The skin must not be punctured to the extent that blood is drawn.

iv. The excess allergen must be removed with cotton wool/tissue, avoiding contamination between allergens.

v. Histamine (positive) and Saline (negative) are used as controls.

Limitations.

Dermatographism may occur as a result of the patient’s skin being excessively sensitive to friction or pressure, rather than to an allergen. If this is the case the negative control will also show a wheal and flare reaction.

i. The very young and very old, have suppressed skin reactivity, however wheal diameters have been shown to increase with age, and are greater in the atopic compared with the non-atopic infant from 4 months. Ageing skin can influence the degree of response as the wheal reaction decreases with age.

ii. Loss of potency of allergen solutions due to incorrect or prolonged storage. Each allergen has an expiry date and manufacturers guidelines on refrigeration and usage.

iii. False positives – irritant reactions, dermatographism, haemorrhage at prick site interpreted as erythema, allergen spread from one site to another, same needle re-used, allergen impurities or inappropriate concentrations.

iv. False negatives – Decreasing potency of allergens, inadequate concentration of allergen, technical error in skin puncture, skin disease or medication. Antihistamines may inhibit the wheal and flare response, potentially causing false-negative results. The period of time antihistamines must be discontinued before testing would depend upon the individual drug, and should be determined by the patient’s clinician. Use of systemic steroids may similarly inhibit results. Topical steroids applied to the prick test area must be avoided.

v. Some agents may induce mast cell histamine release by non-IgE mediated mechanisms (e.g. Morphine, Atracurium).

Complications.

The most common complication is a mild pruritus localised to positive test sites, usually resolving overnight. As with other types of allergy skin testing, the possibility of systemic reaction exists, although Skin Prick Testing to common aeroallergens is widely regarded as a safe procedure.

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5. ROLES AND RESPONSIBILITIES

Interpretation.

Test sites are examined by the appropriately trained registered or unregistered nurse or clinician for a wheal and flare response, 15-20 minutes following the test. Largest diameter of the wheal and/or erythema is measured and recorded in millimetres. The shape of the wheal and flare may be recorded, for further, optional, accuracy, by placing translucent tape directly onto the test area and outlining the reaction with a pen. The “legs” or extensions due to pseudopodia are not taken into account when measuring the wheal. Wheal diameter 3mm larger than the diameter of the negative control would be positive7.

The results of the test are documented in the patient’s medical records, by the nurse or clinician performing the test.

If this result confirms the patient history, then a specific diagnosis may be confidently made, and the procedure description entered into the patient medical notes. Appropriate allergen avoidance advice, and patient-centred literature, ought then to be given to the patient. If the test result contradicts the history, the diagnostic procedure may continue by measurement of specific IgE and perhaps provocation challenge test.

The severity of the disease does not correlate to the wheal size of the prick test.

See Section 4 - Preparation

Unqualified practitioners need to have completed:
(ESR 298) Unregistered practitioners - Handling & Storage of Medicines
(ESR 298) Unregistered practitioners - Assisting with Medication
Or any appropriate equivalent national occupation standards e.g.: Vocational Health & Social Care Awards: CHS2 Assist in the Administration of Medication, CHS3 Administer Medication to Individuals, NVQ Level 3 Medicine Module - directly lifted from the URP procedure

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6. LINKS TO OTHER DOCUMENTS

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7. MONITORING ARRANGEMENTS

If no adverse reaction has occurred, the patient would be free to leave the clinic. To prevent the possibility of spreading the allergens, the patient is advised not to scratch the test area until the wheals have subsided. Patients must be advised to contact the nurse or clinician by telephone, immediately if symptoms of dyspnoea, wheezing, dizziness or severe pruritus develop 5-12 hours after the test (late phase response) or out of office hours to attend the local Accident and Emergency Department.

Appendix
Patient Information Sheet following Skin Prick Testing

Important

Following the skin test it is important that you observe the testing area for the possibility of a late reaction up to 12 hours later.

If any symptoms such as wheezing, rash, itching or dizziness occur during this time please contact either your local General Practitioner, or if you are particularly concerned, your local Accident and Emergency department. Remember to tell the staff you have had a ‘Skin Prick Test’.

Skin prick testing is widely regarded as a completely safe procedure, but please feel free to contact the department, weekdays between 8.30am and 4.30pm, on the above number, if you have any concerns.

Please see the Procedure Monitoring Table for further detail.

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Provenance

Record: 4997
Objective:
Clinical condition:
Target patient group:
Target professional group(s): Secondary Care Doctors
Secondary Care Nurses
Adapted from:

Evidence base

  1. Bernstein, D. (2004) “The Skin Prick Test: More Than Meets The Eye” Annals of Allergy, Asthma and Immunology, 92(6), p.587.
  2. Campbell, T J et al. (2013) “Comparison Of Four Different Skin Prick Test Devices In Allergic And Non-Allergic Subjects” Journal of Allergy and Clinical Immunology, 131(2), p.160.
  3. Ciebiada, M G et al. (2014) “Wheal and Flare Reactions in Skin Prick Tests of Patients Treated With Montelukast Alone Or In Combination With Antihistamines” Inflammation Research, 63(3), pp.191-5.
  4. Devenney, I and Faith-Magnusson, K. (2000) ”Skin Prick Tests May Give Generalised Allergic Reactions In Infants” Annals of Allergy, Asthma and Immunology, 85(6), p.457.
  5. Shytaj, K et al. (2012) “Differences In The Histamine Induced Wheal And Flare Inhibition Between Cetirizine And Loratidine” Pharmacologyonline, 3, pp.6-12.
  6. Walker, S. (2005) “What Is Allergy?” www.internurse.com
  7. Werther, R L et al. (2012) “Variability In Skin Prick Test Results Performed By Multiple Operators Depends On The Device Used” World Allergy Organisation, 5(12), pp.200-4.

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Approved By

Trust Clinical Guidelines Group

Document history

LHP version 1.0

Related information

British Society for Allergy and Clinical Immunology (BSACI)

We have renewed accreditation of the process used by the British Society for Allergy and Clinical Immunology to produce clinical guidelines. The renewed accreditation is valid until 30 January 2023 and applies to guidance produced using the processes described in the BSACI Guideline Production Manual. The original accreditation term began on 30 January 2013.

Procedure monitoring table

Procedure element to be monitored

Standards and Performance indicators

Process for monitoring

Individual or group responsible for monitoring

Frequency or monitoring

Responsible individual or group for development of action plan

Responsible group for review of assurance reports and oversight of action plan

Approved Medicines list lodged with Head of Nursing Medicines Management

The list of approved medicines for SPT is ratified on an annual basis

Agenda item at Speciality Governance Meeting for review of current practice

Pharmacy/ Sarah Denman

Annual

Speciality Governance Meeting

Respiratory Triumvirate Management Team 

Review of incidents reported via DATIX

100% of incidents relating to SPT are reviewed

Agenda item at Speciality Governance Meeting for review of emerging issues/concerns

Nursing Staff

Annual

Speciality Governance Meeting

Respiratory Triumvirate Management Team 

Staff competencies

100% of staff undertaking the procedure are assessed for competency in skin prick testing and aseptic technique??

 

Staff training an agenda item at Speciality Governance Meeting for review of current practice

Nursing Staff

?Bi-annual - may need advice from Allison Scott on this one

Speciality Governance Meeting

Respiratory Triumvirate Management Team

Trust register of unregistered practitioners medicine administration

The Head of Nursing receives a yearly declaration form for unregistered practitioners

Annual Appraisal

Nursing Staff

Annual

Speciality Governance Meeting

Respiratory Triumvirate Management Team

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Equity and Diversity

The Leeds Teaching Hospitals NHS Trust is committed to ensuring that the way that we provide services and the way we recruit and treat staff reflects individual needs, promotes equality and does not discriminate unfairly against any particular individual or group.