Tear total IgE and allergen antibody test (allergy blood test kit)

Key points about this condition

• Diagnosis of allergic conjunctival disease is divided into three stages: clinical diagnosis, clinical definitive diagnosis, and definitive diagnosis
• The tear total IgE test (Allerwatch) is a rapid diagnostic kit that uses immunochromatography and can be interpreted the same day in the outpatient clinic
• The tear IgE positivity rate in vernal keratoconjunctivitis (VKC) is high at 94.7%, while it is only 60–65% in seasonal and perennial allergic conjunctivitis, so false negatives need to be kept in mind
• Serum antigen-specific IgE antibody testing is useful for confirming an overall allergic tendency and identifying the causative antigen, and insurance coverage applies to up to 13 items
• Skin tests (prick test and scratch test) carry a risk of anaphylaxis, so contraindications must be checked before performing them
• Eosinophil testing (Hansel stain) is essential for definitive diagnosis, and the finding of a single eosinophil is positive
• The four tests have different purposes, so it is important to use them according to the diagnostic level

1. What are tear total IgE and allergen antibody tests?

Diagnosis of allergic conjunctival disease is classified into three stages based on the Allergic Conjunctival Disease Clinical Practice Guideline (3rd edition)¹⁾.

Diagnostic level	Required findings
Clinical diagnosis	Clinical findings only
Clinical definitive diagnosis	Clinical findings + allergic predisposition (tear total IgE, skin test, serum allergen-specific IgE)
Definitive diagnosis	Clinical findings + local ocular allergic reaction (eosinophil test)

In this article, “tear total IgE and allergen antibody testing” is a general term for the group of tests that support this diagnostic system. The tear total IgE test can quickly confirm an allergic tendency in the eye on the same day in an outpatient setting, and it is used for clinical definitive diagnosis. Serum allergen-specific IgE antibody testing and skin testing are used to confirm a systemic allergic tendency and identify the causative allergen. A eosinophil test using a conjunctival scraping smear is needed for definitive diagnosis.

Allergic conjunctival disease is highly prevalent, especially in relation to cedar pollinosis, and a 2017 survey found allergic conjunctival disease in about 15–20% of patients visiting ophthalmology facilities nationwide³⁾. Choosing the appropriate tests and understanding the diagnostic system lead to accurate classification and treatment.

Q What does the tear IgE test show?

A

It can determine the presence or absence of an allergic tendency in the eye on the same day in an outpatient visit. Alerwatch Tear IgE is a rapid diagnostic kit that uses immunochromatography, and a positive or weakly positive result is diagnosed as “an allergic tendency in the eye.” Together with clinical findings, it helps with clinical definitive diagnosis. A eosinophil test is separately needed for definitive diagnosis.

2. Tear total IgE test (Alerwatch)

Inada N, Ishimori A, Shoji J. CCL20/MIP-3 alpha mRNA expression in the conjunctival epithelium of normal individuals and patients with vernal keratoconjunctivitis. Graefes Arch Clin Exp Ophthalmol. 2014;252(12):1977-1984. Figure 2. PMCID: PMC4245489. License: CC BY.

In severe vernal keratoconjunctivitis (VKC), the upper palpebral conjunctiva shows a cobblestone pattern formed by densely packed large papillae. This corresponds to the high tear IgE positivity rate (94.7%) in vernal keratoconjunctivitis described in the section “Total Tear IgE Test (Allerwatch).”

Test kit and principle

Total tear IgE is tested using a rapid diagnostic kit based on immunochromatography (Allerwatch Tear IgE, Wakamoto Pharmaceutical / Minaris Medical). In immunochromatography, IgE in the tear fluid binds to colloidal gold-labeled anti-human IgE antibodies on the strip, and capillary action carries it to the solid-phase antibody on the test line, where it is captured to form a colored line.

Test procedure

1. Insert the test strip into the lower conjunctival sac to collect tear fluid
2. Develop the test strip
3. Read the test line and control line visually and determine the result

Result interpretation

Results are evaluated in four categories: positive, weakly positive, negative, and indeterminate. Positive or weakly positive results are diagnosed as having an ocular local allergic predisposition.

Positive rate by disease type

The positive rates of total tear IgE by disease type are shown below²⁾.

Disease type	Positive rate (number of positive cases / total cases)
SAC (seasonal allergic conjunctivitis)	61.9%（52/84）
PAC (perennial allergic conjunctivitis)	65.4%（34/52）
AKC (atopic keratoconjunctivitis)	80.5%（33/41）
VKC (vernal keratoconjunctivitis)	94.7%（36/38）
GPC (giant papillary conjunctivitis)	75.0%（6/8）
Total	72.2%（161/223）

Because the positive rate in SAC/PAC remains only 60-65%, the false-negative rate reaches about 35-38%. Even if the tear IgE test is negative, it is important to make a comprehensive diagnosis together with clinical findings²⁾.

Q Even if the tear IgE test is negative, is allergic conjunctivitis still possible?

A

Yes. In SAC (seasonal allergic conjunctivitis) and PAC (perennial allergic conjunctivitis), the positive rate is about 60-65%, and false negatives occur in about 35-38% of cases. Because diagnosis based on the tear IgE test alone has limitations, it is important to judge comprehensively together with clinical findings (eyelid and conjunctival redness, papillary hypertrophy, itching, etc.) and serum antigen-specific IgE.

3. Serum antigen-specific IgE antibody titer test

Testing method

A blood sample is taken and antigen-specific IgE antibodies in the blood are measured in vitro. It is used to assess systemic allergic predisposition and identify the causative antigen.

Items to test are selected from mites, house dust, cedar pollen, orchard grass, timothy grass, and other allergens that show high positivity rates in patients with allergic conjunctival disease. Insurance coverage applies for up to 13 items per test.

Screening test

The following tests are available as screening tests that can measure multiple items at once.

• View Allergy 39 (Thermo Fisher Diagnostics): Can measure 39 items at once. Insurance-covered
• Mast Immunosystems V (Minaris Medical): Multiple-item simultaneous measurement is possible. Insurance-covered

These tests are useful for screening in first-visit cases where the causative allergen has not yet been narrowed down.

Interpreting the results

If any item shows a positive serum antigen-specific IgE antibody titer, it is diagnosed as having a systemic allergic tendency. Antigen-specific IgE antibodies indicate the antigens to which the patient has been sensitized, but the causative antigen should be determined by considering both the antibody titer and the clinical symptoms (such as worsening during pollen season and relation to the indoor environment).

If the sensitized antigen does not match the actual symptoms, consider the possibility of sensitization to multiple antigens or a lower antibody titer due to long-term sensitization.

4. Skin tests (prick test and scratch test)

Method

There are two types of skin tests for immediate allergic reactions: the prick test and the scratch test. For the test antigens, select several antigens suspected from the clinical symptoms and perform the test. When testing, it is important to perform a positive control (to check for false negatives) and a negative control (to confirm that it is not mechanical urticaria) at the same time.

• Prick test: Place allergen solution on the flexor side of the forearm and introduce the antigen by pricking the skin with a dedicated needle
• Scratch test: Make a shallow scratch in the skin with a dedicated device, then apply the allergen solution so it can penetrate into the skin

Criteria for judgment

Use the longest diameter of the wheal and the average of that and the perpendicular diameter at its midpoint as the size of the reaction. A wheal diameter of 3 mm or more, or a reaction at least half the size of the positive control wheal, is judged positive. Judgement is usually made 15 to 20 minutes later.

Contraindications and precautions

Precautions before performing skin tests

Skin testing may trigger allergic symptoms during the examination. For patients who fall into the following categories, consider performing it with caution or switching to serum allergen-specific IgE testing.

• Patients with poorly controlled bronchial asthma
• Patients who may develop anaphylaxis with a small amount of allergen
• Patients with serious cardiovascular disease, such as coronary artery disease or life-threatening arrhythmia

Histamine H₁ receptor antagonists (antihistamines) and tricyclic antidepressants can affect skin test results. For patients taking these drugs, either allow a stop period before testing or switch to serum allergen-specific IgE testing.

Q What precautions should be taken when performing skin tests?

A

Perform positive and negative controls at the same time to confirm the reliability of the test. In patients with poorly controlled bronchial asthma or those at risk of anaphylaxis, carefully consider whether to perform the test and consider switching to serum IgE testing. Because antihistamines and tricyclic antidepressants can affect the results, checking the medications before testing is essential.

5. Comparison of the tests and when to use each

Comparison of the features of the four tests

Test	Target of evaluation	Sensitivity in VKC	Insurance coverage	Features
Tear total IgE (Allerwatch)	Local ocular allergic predisposition	94.7%	Yes, easy	Can be determined on the same day in the outpatient clinic
Serum allergen-specific IgE	Systemic allergic predisposition and identification of the causative allergen	—	Available (up to 13 items)	Useful for identifying the causative allergen
Skin test	Systemic allergic predisposition	—	Available	Risk of anaphylaxis
Eosinophil test	Local ocular allergic reaction	—	Yes	Essential for definitive diagnosis

Practical clinical testing flow

The basic step-by-step approach to testing in clinical practice is shown below¹⁾.

1. Suspect allergy based on clinical findings (clinical diagnosis): check for findings such as itching, redness, and papillary proliferation
2. Confirm an allergic predisposition (clinical confirmation): confirm it with tear IgE or serum allergen-specific IgE. If you want to identify the causative allergen, serum IgE is useful
3. Make a definitive diagnosis when needed (definitive diagnosis): confirm the local ocular allergic reaction with an eosinophil test

Tear IgE testing is useful because it provides same-day results in the outpatient clinic, but false negatives in SAC/PAC need to be considered. If skin testing is difficult because of the risk of anaphylaxis or other reasons, switch to serum allergen-specific IgE testing.

6. Detailed test principles and eosinophil testing

IgE and immediate allergic reactions

IgE is the central immunoglobulin in immediate (type I) allergic reactions. It is bound via the high-affinity IgE receptor (FcεRI) on the surface of sensitized mast cells and basophils. When the antigen enters again, IgE cross-links, degranulation occurs, and inflammatory mediators such as histamine and leukotrienes are released.

In the eye, many mast cells are present in the conjunctiva, and this reaction causes allergy symptoms such as redness, itching, and tearing. The total IgE level in tears reflects the degree of local ocular sensitization.

Principle of immunochromatography

The principle of the immunochromatographic method used for AllerWatch tear IgE is as follows.

• Tear IgE binds to the gold colloid-labeled anti-human IgE antibody on the strip
• It moves along the strip by capillary action
• The antibody immobilized on the test line captures IgE, forming a colored line
• When IgE is present above a certain amount, the colored line becomes visible and the result is judged positive

Serum IgE measurement methods

The following methods are used to measure antigen-specific IgE in serum.

• ImmunoCAP method (fluoroenzyme immunoassay): the most widely used quantitative method. High-sensitivity measurement is possible with a very small sample
• MAST method (CAP-RAST method): a detection method using immobilized allergen
• Quantitative values are expressed in UA/mL (or kU/L), and 0.35 kU/L or higher is often considered positive

Eosinophil testing (definitive diagnosis)

Eosinophil testing is a method in which a conjunctival scraping smear is stained with Hansel stain, and the presence or absence of eosinophils in the smear is judged under a light microscope. If even one eosinophil is confirmed under the microscope, the test is judged positive and an allergic conjunctival disease is definitively diagnosed.

If bleeding is seen during specimen collection, blood cells may have contaminated the sample, so the other eye should be tested again for assessment.

Eosinophils are detected more often in severe cases (VKC・AKC), and may not be detected in SAC/PAC. It is used when a definitive diagnosis is needed or when objectively assessing severity.

7. Latest research and future prospects

Medical disclaimer

The following content is currently in the research stage or under development, and may differ from standard tests available at general ophthalmology outpatient clinics. It is reference information for professionals regarding future medical advances.

Measurement of antigen-specific IgE in tear fluid

Research and development are advancing on kits that measure specific IgE in tear fluid (for example, cedar-specific IgE). If, in addition to total tear IgE, the locally sensitizing allergen in the eye can be directly identified, it may become possible to diagnose the causative allergen on the same day in the outpatient clinic without blood sampling. At present, this remains at the research stage.

Severity assessment using biomarkers

Biomarkers such as periostin, eotaxin, and TARC (CCL17) in tear fluid are being studied for possible use in assessing severity. In particular, periostin is drawing attention as an indicator of Th2 inflammation, and it has been suggested that it may reflect disease activity in VKC and AKC⁴⁾.

Antibody titer monitoring in allergen immunotherapy

Studies are underway on monitoring changes in serum specific IgE antibody titers to evaluate the effectiveness of sublingual immunotherapy and subcutaneous immunotherapy for cedar pollen allergy⁵⁾. It has been reported that IgE antibody titers may temporarily rise and then fall with immunotherapy, and use of tear IgE monitoring is also being considered.

Allergy testing in children

In pediatric allergic conjunctival disease, especially VKC, skin testing can be difficult to perform, and tear IgE and serum IgE can be useful. Large-scale evaluation of the sensitivity and specificity of each test in children, as well as research on recommended testing procedures, is needed⁶⁾.

8. References

1. 日本眼科アレルギー学会診療ガイドライン作成委員会. アレルギー性結膜疾患診療ガイドライン（第3版）. 日眼会誌. 2021;125(8):741-785.
2. 庄司純, 内尾英一, 海老原伸行, 大橋裕一, 大野重昭, 岡本茂樹, 他. アレルギー性結膜疾患診断における自覚症状，他覚所見および涙液総IgE検査キットの有用性の検討. 日眼会誌. 2012;116(5):485-493. http://journal.nichigan.or.jp/Disp?mag=0&number=5&start=485&style=abst&vol=116&year=2012.
3. 岡本茂樹, 内尾英一, 海老原伸行, 他. 2017年度日本眼科アレルギー学会アレルギー性結膜疾患実態調査. 日眼会誌. 2022;126(7):625-635.
4. Fujishima H, Okada N, Matsumoto K, Fukagawa K, Igarashi A, Matsuda A, Ono J, Ohta S, Mukai H, Yoshikawa M, Izuhara K. The usefulness of measuring tear periostin for the diagnosis and management of ocular allergic diseases. J Allergy Clin Immunol. 2016;138(2):459-467.e2. doi:10.1016/j.jaci.2015.11.039.
5. 鈴木茂伸, 堀口裕正, 遠藤昌夫. スギ花粉症の舌下免疫療法とアレルゲン特異的IgE抗体価の推移. アレルギー. 2018;67(6):704-711.
6. Leonardi A, Bogacka E, Fauquert JL, Kowalski ML, Groblewska A, Jedrzejczak-Czechowicz M, et al. Ocular allergy: recognizing and diagnosing hypersensitivity disorders of the ocular surface. Allergy. 2012;67(11):1327-37. doi:10.1111/all.12009. PMID:22947083.