There are various sizes of ALCAT panels and they are likely reported with multiple units of CPT code 83516 (Immunoassay for analyte other than infectious agent antibody or infectious agent antigen; qualitative or semiquantitative, multiple step method). For example, the ALCAT Platinum Comprehensive Panel might be reported with 320 units of code 83516.

The Antigen Leukocyte Antibody Test (ALCAT) is intended to diagnose intolerance to foods and other environmental agents. It is a blood test that assesses the response of leukocytes and platelets to a panel of foods and/or other environmental agents, by measuring the change in size and number of cells following exposure to a specific agent.

ALCAT is a blood test that is intended to diagnose intolerance to foods and other environmental agents. There is a lack of published research on the diagnostic accuracy of the test; therefore it is not possible to determine the sensitivity, specificity, and/or predictive value of the test compared with alternatives. A few low-quality studies report improvement in outcomes following use of ALCAT, but it is not possible to determine whether these changes occur as a result of the test itself, versus bias, variation in the natural history of the condition, and/or the placebo effect. Guidelines for the diagnosis of food allergy from the National Institute of Allergy and Infectious Disease (NIAID) do not discuss use of ALCAT. Due to the limitations of the evidence base, and lack of acceptance of the test as a component of standard care by experts in this area, ALCAT is considered not medically necessary for all indications.

Environmental illness refers to a physiologic reaction that is triggered by an exogenous agent, which can be ingested, inhaled, or exposed through direct contact with skin. The physiologic reaction can be an immunologic response or a nonimmunologic response. An adverse physiologic reaction to exogenous antigens has been proposed to play a causative role in a wide variety of illnesses, including allergies, gastrointestinal (GI) tract disorders such as irritable bowel syndrome, eczema, chronic fatigue, and migraine headache.1 

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Food allergy is the most well-defined type of environmental illness and is estimated to affect 8% of children.2 In most cases, true food allergy is characterized by a classic immunologic response, ie, an immunoglobulin E?mediated reaction in response to a specific protein allergen. Reactions can range from mild symptoms to life-threatening anaphylaxis. Current guidelines for the diagnosis and management of food allergies have been developed by NIAID.3 

Food intolerance is a broader term that overlaps with food allergy but is less well-defined. Food intolerance refers to physiologic reactions that are triggered by a particular food, but which are not immune-mediated.2 It is hypothesized that physiologic reactions to food may manifest as a range of nonspecific symptoms, such as GI complaints, headache, fatigue, and musculoskeletal complaints and that these symptoms may become chronic with repeated exposure. An example of food intolerance, distinguished from a true food allergy, is lactose intolerance, in which dairy products incite nonimmunologic reaction that can lead to a constellation of GI symptoms.

Treatment of environmental illness primarily involves avoidance of the inciting agent. Acute allergic reactions are treated in the same way as other types of allergies with antihistamines, steroids, and supportive measures. In cases of severe allergy where an agent cannot be definitively avoided, patients can carry and self-administer auto-injectable epinephrine when needed. Prophylactic antihistamines can also be used to prevent or lessen reactions. Allergy immunotherapy may be appropriate for selected allergens.

For patients with food intolerance that is not allergic in nature, identification of the inciting agent(s) can be difficult because the symptoms are chronic in nature. Use of an elimination diet is considered the best way to identify intolerant agents. In an elimination diet, 1 specific food or food group is eliminated from the diet for a specified period of time and symptoms observed. Following the elimination period, a rechallenge can be performed to ascertain whether symptoms return. Elimination diets often need to be done sequentially with a large number of items, so that the process can be lengthy and cumbersome. 

Antigen Leukocyte Antibody Test 

ALCAT is intended to identify foods and other environmental agents for which an individual may have intolerance. It is not intended to diagnose food allergy.4 The test is based on the theory that a substantial increase in leukocyte size and number is characteristic of an intolerant response. Identifying the specific inciting agent facilitates avoidance of that agent, which may lead to a reduction in symptoms. In this regard, ALCAT testing has been used as a tool for developing an elimination diet that is targeted to the most likely offending agents.

The test is performed by taking a sample of blood, which is first treated to remove the red blood cells and tested to determine the baseline number and size of leukocytes and platelets. Measurement of size and count of cells is performed by the Coulter technique, which is a standard technique in clinical hematology. Next, a small quantity of blood is incubated with multiple agents. Following exposures, change in the number and size of cells is determined for each exposure. A 10% increase in the size of leukocytes is considered characteristic of a response to an intolerant agent.

The ALCAT website (Cell Sciences Systems, Deerfield Beach, FL) lists 11 separate panels consisting of various combinations of foods, herbs, food additives/coloring, and environmental chemicals. The total number of agents tested in these panels range from 70 to 320.4 

This policy was developed in February 2014 with literature review covering the period of January 1, 1990, through December 31, 2013, and updated periodically with literature review. The most recent update covers includes literature review covering January 1, 2014, through January 30, 2015.

Assessment of a diagnostic technology typically focuses on 3 categories of evidence: (1) technical performance (test-retest reliability or interrater reliability); (2) diagnostic accuracy (sensitivity, specificity, and positive and negative predictive value) in relevant populations of patients; and (3) demonstration that the diagnostic information can be used to improve patient outcomes. In addition, subsequent use of a technology outside of the investigational setting may also be evaluated. These categories of evidence, although not always evaluated in sequence, can be considered similar to the 4 phases of therapeutic studies.

There is lack of full-length, peer-reviewed publications that evaluate the utility of the Antigen Leukocyte Antibody Test (ALCAT). Many citations from the manufacturer’s website and other internet sources were abstracts presented at scientific meetings or articles published in non-peer-reviewed journals that are not indexed in MEDLINE. The following literature review summarizes the most relevant publications that were identified through MEDLINE and supplemental searches.

Technical Performance

The technical performance of the test refers to the ability of the test to accurately identify changes in the number and size of leukocytes and platelets. The technology uses the “Coulter Counter” technique that is in widespread use in clinical medicine, and thus is expected to have an accuracy that is similar to standard technology for counting and measuring cells.

The reproducibility of the test is uncertain.5 There were no publications identified that evaluated test-retest reproducibility over time.

Diagnostic Accuracy

There is not a widely accepted criterion standard test for food and environmental intolerance. The doubleblind food challenge test may be considered an appropriate reference standard, but there are deficiencies in the definitions and interpretation of food challenge results. There were no published studies identified that reported on the sensitivity and specificity of ALCAT, in comparison with a double-blind food challenge. One study from 1995 compared ALCAT and cytotoxic testing, which is not a test routinely used in clinical care at present, in 56 children between the ages of 0.5 and 16 years.6 This study reported that results of the 2 tests were consistent in two thirds of the patients.

Impact on Health Outcomes

One randomized controlled trial was identified that evaluated the use of ALCAT in facilitating weight loss, changes in body composition, and health symptoms.7 One hundred patients were recruited through an advertisement in a fitness newspaper. Eligibility criteria included at least 2 symptoms that had a “severe effect”, as measured by the Disease Symptoms Inventory (DSI). Patients were randomized to ALCAT testing followed by dietary modifications versus a control group that was instructed to pursue a diet of their own choosing. The ALCAT group received dietary guidance on dietary changes that were recommended based on ALCAT results. Outcomes were measured after 4 weeks of the intervention and included changes in weight, body composition and symptoms on the DSI. Eight participants were lost to follow-up, 7 in the control group and 1 in the ALCAT group.

There was a greater reduction in weight in the ALCAT group compared with the control group (-1.04 kg vs +0.32 kg, p<0.001), as well as a greater reduction in the percent body fat (-1.2% vs +0.7%, p<0.001). There were also significantly better scores on the final DSI outcomes for the ALCAT group. Of 20 symptoms included on the DSI, the final scores were significantly better for the ALCAT group on 18 of 20 symptoms. The results of this study have limited clinical relevance because the outcomes reported (weight loss and body composition) are not applicable to the main clinical use of the test. Also, the validity of the results is reduced by limitations in patient selection, lack of blinding, and provision of dietary guidance to the ALCAT group but not the control group.

A small number of case series have been published, reporting outcomes following ALCAT testing and treatment based on ALCAT results. These studies are not sufficient to establish efficacy because they cannot control for the natural history of the disorder or for nonspecific factors such as the placebo effect. An example of 1 such study is by Solomon.1 In this publication, 172 patients with a range of symptoms were tested with ALCAT. Treatment was a food elimination diet, and/or allergy immunotherapy, based on ALCAT results. Follow-up allergy testing was performed with serial end point titration at 3 to 6 months after treatment. Outcomes were measured at 1 to 2 years posttreatment by an independent reviewer who asked subjects to rate the effectiveness of treatment on a 1-to-10 scale. For elimination diets, a range of improvement in individual symptoms of 20% to 82% was reported, and for immunotherapy a range of improvement of 9% to 75% was reported. 

Another uncontrolled study that used ALCAT as the basis for an elimination diet was published by Mylek in 1995.8 This study enrolled 72 patients with a range of symptoms that were considered to be the result of food intolerance. The largest percent improvement in symptoms was reported for arthritis (83%), urticaria (75%), bronchitis (70%), and gastroenteritis (70%). A smaller degree of improvement was reported for the symptoms of hyperreactivity (32%), rhinitis (47%), and atopic dermatitis (49%). 

Ongoing and Unpublished Clinical Trials  

A search of ClinicalTrials.gov in January 2015 found no relevant ongoing studies of the ALCAT test.

Summary of Evidence

The Antigen Leukocyte Antibody Test (ALCAT) is a blood test that is intended to diagnose intolerance to foods and other environmental agents. There is a lack of published research on the diagnostic accuracy of the test; therefore it is not possible to determine the sensitivity, specificity, and/or predictive value of the test compared with alternatives. A few low-quality studies report improvement in outcomes following use of ALCAT, but it is not possible to determine whether these changes occur as a result of test itself, versus bias, variation in the natural history of the condition, and/or the placebo effect. Guidelines for the diagnosis of food allergy from the National Institute of Allergy and Infectious Disease do not discuss use of ALCAT. Due to the limitations of the evidence base, and lack of acceptance of the test as a component of standard care by experts in this area, ALCAT is considered not medically necessary for all indications.