Laboratory Testing Requirements Before Starting SLIT
Before initiating sublingual immunotherapy, patients must have documented IgE sensitization to the relevant allergen through either positive skin prick testing or allergen-specific IgE blood testing—no other laboratory tests are required. 1
Essential Pre-Treatment Testing
Allergy Confirmation (Required)
- Eligible patients must demonstrate both clinical history of allergy AND positive IgE testing through one of two methods: 1
- Skin prick test showing positivity to the specific allergen, OR
- Serum allergen-specific IgE blood test (in vitro testing) 1
- The American Academy of Otolaryngology-Head and Neck Surgery confirms that both history and testing are mandatory to confirm allergies before initiating SLIT 1
No Additional Laboratory Tests Required
- No routine blood work, complete blood count, comprehensive metabolic panel, or other laboratory studies are necessary before starting SLIT 1
- The guidelines from the American Academy of Allergy, Asthma, and Immunology and European Academy of Allergy and Clinical Immunology do not mandate any laboratory testing beyond allergen-specific IgE confirmation 1, 2
Clinical Assessment Requirements (Beyond Laboratory Testing)
Symptom Severity Documentation
- Patients should have at least moderate symptom severity, as those with very mild symptoms create difficulties in detecting treatment differences 1
- Ideal candidates demonstrate inadequate response to optimal pharmacologic treatment with antihistamines and intranasal corticosteroids 2
Respiratory Function Considerations
- While not a laboratory test per se, patients with asthma should have controlled disease (FEV1 >80% predicted) before initiating SLIT 3
- The American Academy of Allergy, Asthma, and Immunology notes that SLIT has not been extensively studied in high-risk asthmatic patients 4
Common Pitfalls to Avoid
Over-Testing
- Do not order unnecessary baseline laboratory panels (CBC, CMP, liver function tests, etc.) as these are not indicated and add unnecessary cost 1
- Baseline IgE levels beyond allergen-specific testing are not required for treatment initiation 1
Under-Testing
- Never initiate SLIT based on clinical history alone without objective IgE confirmation—this violates fundamental patient selection criteria 1
- Ensure testing corresponds to the specific allergen being administered in SLIT 1
Timing Considerations
- A predefined post hoc analysis correlating treatment effect with baseline levels of antigen-specific IgE may be useful for research purposes but is not required for clinical practice 1
- For polysensitized patients, confirm IgE sensitization to the specific allergen being treated, as cross-reactivity can confound efficacy evaluation 1