Editing Allergy (section)

===Blood testing===
An allergy [[blood test]] is quick and simple and can be ordered by a licensed health care provider (''e.g.'', an allergy specialist) or general practitioner. Unlike skin-prick testing, a blood test can be performed irrespective of age, skin condition, medication, symptom, disease activity, and pregnancy. Adults and children of any age can get an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often gentler than several skin pricks.

An allergy blood test is available through most [[Medical laboratory|laboratories]]. A sample of the patient's blood is sent to a laboratory for analysis, and the results are sent back a few days later. Multiple allergens can be detected with a single blood sample. Allergy blood tests are very safe since the person is not exposed to any allergens during the testing procedure. After the onset of anaphylaxis or a severe allergic reaction, guidelines recommend emergency departments obtain a time-sensitive blood test to determine blood tryptase levels and assess for mast cell activation.<ref>{{Cite journal |last=Reinhold |first=Lauren |date=February 2023 |title=An Update on Test use Evaluation of Serum Tryptase Levels |url=https://www.jacionline.org/article/S0091-6749(22)01692-X/fulltext |journal=The Journal of Allergy and Clinical Immunology |volume=151 |issue=2|pages=AB10 |doi=10.1016/j.jaci.2022.12.038 }}</ref>

The test measures the concentration of specific [[IgE|IgE antibodies]] in the blood. [[Quantitative analysis (chemistry)|Quantitative]] IgE test results increase the possibility of ranking how different substances may affect symptoms. A rule of thumb is that the higher the IgE antibody value, the greater the likelihood of symptoms. Allergens found at low levels that today do not result in symptoms cannot help predict future symptom development. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain [[cross-reactivity]].<ref>{{cite journal | vauthors = Yunginger JW, Ahlstedt S, Eggleston PA, Homburger HA, Nelson HS, Ownby DR, Platts-Mills TA, Sampson HA, Sicherer SH, Weinstein AM, Williams PB | display-authors = 6 |title=Quantitative IgE antibody assays in allergic diseases |journal=Journal of Allergy and Clinical Immunology |date=June 2000 |volume=105 |issue=6 |pages=1077–84 |doi=10.1067/mai.2000.107041| pmid = 10856139 |doi-access=free }}</ref><ref>{{cite journal | vauthors = Sampson HA | title = Utility of food-specific IgE concentrations in predicting symptomatic food allergy | journal = The Journal of Allergy and Clinical Immunology | volume = 107 | issue = 5 | pages = 891–96 | date = May 2001 | pmid = 11344358 | doi = 10.1067/mai.2001.114708 }}</ref>

A low total IgE level is not adequate to rule out [[Sensitization (immunology)|sensitization]] to commonly inhaled allergens.<ref name="pmid12911420"/> [[statistics|Statistical methods]], such as [[ROC curve]]s, predictive value calculations, and likelihood ratios have been used to examine the relationship of various testing methods to each other. These methods have shown that patients with a high total IgE have a high probability of allergic sensitization, but further investigation with allergy tests for specific IgE antibodies for a carefully chosen of allergens is often warranted.

Laboratory methods to measure specific IgE antibodies for allergy testing include [[enzyme-linked immunosorbent assay]] (ELISA, or EIA),<ref name=webmd>{{cite web|url=http://www.webmd.com/allergies/guide/blood-test|title=Blood Testing for Allergies|access-date=5 June 2016|website=[[WebMD]]|url-status=live|archive-url=https://web.archive.org/web/20160604101105/http://www.webmd.com/allergies/guide/blood-test|archive-date=4 June 2016}}</ref> [[radioallergosorbent test]] (RAST),<ref name=webmd/> fluorescent enzyme [[immunoassay]] (FEIA),<ref name="KhanUeno-Yamanouchi2012">{{cite journal | vauthors = Khan FM, Ueno-Yamanouchi A, Serushago B, Bowen T, Lyon AW, Lu C, Storek J | title = Basophil activation test compared to skin prick test and fluorescence enzyme immunoassay for aeroallergen-specific Immunoglobulin-E | journal = Allergy, Asthma, and Clinical Immunology | volume = 8 | issue = 1 | pages = 1 | date = January 2012 | pmid = 22264407 | doi = 10.1186/1710-1492-8-1 | pmc=3398323 | doi-access = free }}</ref> and [[chemiluminescence immunoassay]] (CLIA).<ref>Casas ML, Esteban Á, González-Muñoz M, Labrador-Horrillo M, Pascal M, & Teniente-Serra A (2020). VALIDA project: Validation of allergy in vitro diagnostics assays (Tools and recommendations for the assessment of in vitro tests in the diagnosis of allergy). In Advances in Laboratory Medicine (Vol. 1, Issue 4). Walter de Gruyter GmbH. https://doi.org/10.1515/almed-2020-0051</ref><ref>Bulat Lokas S, Plavec D, Rikić Pišković J, Živković J, Nogalo B, & Turkalj M (2017). Allergen-Specific IgE Measurement: Intermethod Comparison of Two Assay Systems in Diagnosing Clinical Allergy. Journal of Clinical Laboratory Analysis, 31(3), e22047. https://doi.org/10.1002/jcla.22047</ref>