Current Procedural Terminology (CPT) codes are a standardized language used across healthcare to describe medical, surgical, and diagnostic services for billing and reimbursement. CPT code 95004 specifically identifies percutaneous allergy testing, often called a scratch or prick test. This diagnostic method involves introducing small amounts of allergenic extracts into the skin to test for immediate-type hypersensitivity reactions. The code’s application is based on the number of individual allergens tested during a single patient session.
The Percutaneous Scratch Test Procedure
The percutaneous test is a simple and quick method for diagnosing immediate allergic reactions. The procedure begins with a healthcare professional cleaning and marking the testing site, usually the forearm or upper back.
Small drops of different liquid allergenic extracts and control solutions are placed onto the marked skin surface. A specialized sterile lancet is then used to lightly puncture the skin beneath each drop, creating a tiny break in the outermost layer. This allows the allergen extract to seep into the skin’s surface without causing bleeding or significant pain.
The patient waits approximately 15 to 20 minutes for the immune system to respond. If sensitized, mast cells rapidly release histamine, causing a localized reaction. The resulting swelling and redness are then measured and documented by the healthcare provider.
Common Allergens Identified by This Method
This procedure tests for immediate hypersensitivity reactions mediated by Immunoglobulin E (IgE) antibodies. It identifies a wide spectrum of environmental triggers that cause symptoms like allergic rhinitis, asthma, or dermatitis.
Common tested allergens include seasonal pollen from trees, grasses, and weeds. Indoor allergens routinely tested are dust mites, mold spores, and dander from pets like cats and dogs. While primarily used for inhalant allergies, the test can also screen for certain immediate food allergies.
How CPT 95004 is Used for Billing
CPT 95004 is billed on a unit-of-service basis, not once per session. One unit of the code is reported for each individual allergenic extract tested. For example, if a patient is tested against 18 allergens, the claim lists CPT 95004 with 18 units.
Insurance payers often establish a maximum number of tests they will cover per session. Many payers will scrutinize claims reporting an unusually high volume of tests, sometimes exceeding 70 or 80 units in a single day. Providers must maintain detailed documentation justifying the medical necessity for every allergen tested to ensure proper reimbursement. Control tests, such as positive (histamine) and negative (saline) controls, are not separately billable under CPT 95004, as their cost is bundled into the primary procedure.
Preparing for the Test and Interpreting Results
Patient preparation directly influences the accuracy of the test results. Patients must stop taking oral antihistamines, typically for five to seven days, before the scheduled test date. Antihistamines interfere with the histamine response the test measures, potentially causing a false-negative result.
After the 15- to 20-minute observation period, the provider measures any visible skin reactions. A positive result is a raised, pale bump called a wheal, surrounded by redness known as a flare. The size of the wheal and flare is measured and recorded; a wheal diameter at least three millimeters greater than the negative control is considered clinically positive.
The reaction size indicates the degree of skin sensitivity, correlating with the amount of IgE antibody present. However, a larger skin reaction does not predict the severity of a patient’s real-world allergic symptoms. Results are evaluated alongside the patient’s medical history and reported symptoms to formulate a targeted treatment plan, such as avoidance strategies or immunotherapy.