1. Component Resolved Diagnostics
Roisin Fitzsimons
Consultant Nurse
Guy’s and St Thomas NHS Foundation Trust

2. Overview of session
Current diagnostic methods What is component resolved diagnostics (CRD)? Application to practice

3. Allergy Diagnosis
History Skin Prick Testing (SPT) Specific IgE Testing (SpIgE) Provocation - Oral food challenge

4. What is CRD?

5. Protein Formation

6. Major peanut allergens
Peanut components
Ara h 2
Ara h 1
Ara h 8
Ara h 9
Ara h 3
Major peanut allergens

7. Features of peanut components
Seed storage proteins
PR10 proteins
Lipid Transfer Proteins (LTP)
Ara h 1,2,3 - major peanut allergens
Ara h 8
Ara h 9
Responsible for primary sensitisation
Recognition of similar structures
Found in nuts, seeds, legumes
Bet v 1 homologue (Apple Mal d 1)
Heat resistant and stable
May cause systemic, severe reactions
Altered by heating/gastric juices
Risk of severe reactions
Not easily broken down
Localised symptoms
Cross-reactivity with Pru p 3
Present in large quantities
Pollen food syndrome
Common in Southern European countries
Can we predict severity of allergy?
Formed of components
Structure and significance varies

8. Relevance to practice
Can we predict severity of a reaction? Ara h 1,2,3 – primary sensitisation to peanut Ara h 8 – cross reactivity with Birch pollen

9. Case study - Rose
8 year old Sesame allergic Allergic Rhinitis FH peanut allergy Always avoided peanuts
Immunological investigations SPT 2mm SpIgE 4.38ku/ml Ara h 1 – 0.00 Ara h 2 – 0.16 Ara h 3 – 0.00 Ara h 8 – 6.24

10. What next? Allergic; avoid peanuts? Tolerant; introduce peanuts?
Probably OAS; introduce peanuts with caution?
Not sure; OFC?

11. Proceeded to OFC Tolerated first two doses Third dose – oral pruritus, no objective symptoms Repeated dose – worsening of pruritus, not distractible What next?

12. Implications for practice
Ara h 2 clinically relevant for predicting positive OFC Presence of Ara h 1&3 increases likelihood of allergy Ara h 8 may suggest OAS Listen to your patient and family

13. Summary
CRD useful in aiding diagnosis Should not replace clinical history and holistic evaluation Easier to predict allergy than tolerance

14. Reference list
Beyer K et al 2015, Allergy; 70: 90–98. Dang T D et al, 2012, J Allergy Clin Immunol;129: Nicolaou N et al, 2010, J Allergy Clin Immunol; 125:191-7 Asarnoj A and Movérare R et al, 2010, Allergy