The ImmunoCAP^® Specific IgE Blood Test: Facts Every Clinician Should Know

Primary care clinicians routinely see patients with respiratory complaints. Managing the common symptoms of chronic cough, persistent nasal congestion, and postnasal drip can be frustrating for a practitioner—unless you accurately identify the underlying cause of the problem first. Unfortunately symptomatic treatment with antihistamines and nasal sprays, in many cases, gives only temporary relief; all too often the patient calls again for help. So how can you ensure you’re making the right diagnosis (and with it, the right treatment plan)? The key is using your clinical impression based on history and physical exam—and then using appropriate objective evidence or laboratory testing to confirm or rule out allergies as the underlying cause.

In my view, the first challenge in diagnosing an upper respiratory condition is to figure out if the patient has an infection. If the patient is afebrile, without pain in a specific area, without nasal discharge or sputum, and the symptoms are chronic, more than likely you can rule out an infection. If the patient is persistently sneezing, experiencing itching in the nose, eyes, and throat, allergy would seem to be a potential underlying problem. So why would you need a lab test? There are several reasons: Symptom presentations often overlap between allergic and non-allergic conditions, so to aid the clinician in making an accurate diagnosis, it’s best to have objective evidence. In fact, when using history and physical alone, it has been estimated that the clinician can correctly diagnose an allergic condition only 50% of the time.¹

ImmunoCAP, a late-generation specific IgE assay, provides a physician with an accurate, quantitative, specific assessment of a patient’s allergic status. When positive, ImmunoCAP results will provide information regarding what a patient is allergic to. When results are negative, the clinician can rule out allergies and shift the evaluation to other potential symptom causes. For the primary care clinician, ImmunoCAP offers several advantages: it is safe, a patient does not have to be off of their medications, and the results are quantitative to help differentiate a strong allergic reaction from a mild one. In addition, the process of conducting this testing has been simplified from the past. A clinician can order a pre-selected respiratory profile, which will include significant aeroallergens in your region of the country, which will provide greater than 95% positive predictive value.^2-4 The respiratory profile includes representative pollens (trees, grasses, and weeds), dust mites, animal saliva and dander, and molds. The information you glean from the ImmunoCAP testing will enable you to target your treatment selection and advise your patient on the proper environmental precautions to decrease or eliminate their symptoms.

References

1. Homburger HA. Diagnosing allergic diseases in children: practical recommendations for consulting pathologists. Arch Pathol Lab Med. 2004;128:1028-1031.
2. Yunginger JW, Ahlstedt S, Eggleston PA, et al. Quantitative IgE antibody assays in allergic diseases. J Allergy Clin Immunol. 2000;105:1077-1084.
3. Poon AW, Goodman CS, Rubin FJ. In vitro and skin testing for allergy: comparable clinical utility and costs. Am J Managed Care. 1998;4:969-985.
4. Choo-Kang LR. Becoming a complete “asthmologist.” Chest. 2005;128:3093-3096.