CMS Autonomic Function Tests Form

Effective Date


Last Reviewed


Original Document


Background for this Policy

Summary Of Evidence


Analysis of Evidence


Notice: It is not appropriate to bill Medicare for services that are not covered (as described by this entire LCD) as if they are covered. When billing for non-covered services, use the appropriate modifier.

Compliance with the provisions in this policy may be monitored and addressed through post payment data analysis and subsequent medical review audits.

History/Background and/or General Information

The autonomic nervous system (ANS) regulates physiologic processes, such as blood pressure, heart rate, body temperature, digestion, metabolism, fluid and electrolyte balance, sweating, urination, defecation, sexual response, and other processes. Regulation occurs without conscious control, i.e., autonomously. The ANS has two major divisions: the sympathetic and parasympathetic systems. ANS testing measures alterations in the R-R interval of the electrocardiogram (ECG) in response to parasympathetic and sympathetic system stimulation. The aim of such testing is to correlate signs and symptoms of possible autonomic dysfunction with objective measurement in a way that is clinically useful. Many organs are controlled primarily by either the sympathetic or parasympathetic system, although they may receive input from both; occasionally, functions are reciprocal (e.g., sympathetic input increases heart rate; parasympathetic decreases it).

The sympathetic nervous system is catabolic and activates fight-or-flight responses. Thus, sympathetic output increases heart rate and contractility, bronchodilation, hepatic glycogenolysis and glucose release, BMR (basal metabolism rate), and muscular strength; it also causes sweaty palms. Less immediately-life-preserving functions (e.g., digestion, renal filtration) are decreased.

The parasympathetic nervous system is anabolic; it conserves and restores. Gastrointestinal secretions and motility (including evacuation) are stimulated, heart rate is slowed, and blood pressure decreases.

Disorders of the ANS can affect any system of the body; they can originate in the peripheral or central nervous system and may be primary or secondary to other disorders. Symptoms suggesting autonomic dysfunction include orthostatic hypotension, heat intolerance, nausea, constipation, urinary retention or incontinence, nocturia, impotence, and dry mucous membranes. If a patient has symptoms suggesting autonomic dysfunction, cardiovagal, adrenergic, and sudomotor tests are usually done to help determine severity and distribution of the dysfunction.

Drugs can have substantial effects on the results of ANS testing and are a common cause of falsely abnormal results. Patients should refrain from caffeine, nicotine, and alcohol at least 3 hours prior to testing. All medications with adrenergic and anticholinergic properties need to be discontinued at least 48 hours prior to the study. These would include but are not limited to the following drugs: chlorpromazine, thioridazine, the tricyclic and tetracyclic antidepressants, bupropion, mirtazapine, venlafaxine, clonidine, alpha-blockers, beta-blockers, calcium channel blockers, opiates, topical capsaicin, and diphenhydramine.

ANS testing can be grouped into three general categories:

  • Cardiovagal innervation is a test that provides a standardized quantitative evaluation of vagal innervation to parasympathetic function of the heart. Responses are based on the interpretation of changes in continuous heart recordings in response to standardized maneuvers and include heart rate response to deep breathing, Valsalva ratio, and 30:15 ratio heart rate responses to standing. A tilt table is usually used for testing.
  • Vasomotor adrenergic innervation evaluates adrenergic (sympathetic) innervation of the circulation and of the heart in autonomic failure. The following tests are included: beat-to-beat blood pressure and R-R interval response to Valsalva maneuver, sustained hand grip, and blood pressure and heart rate responses to tilt-up or active standing. The testing must be performed with a tilt table.
  • Sudomotor function testing is used to evaluate and document neuropathic disturbances that may be associated with pain. The quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test (TST), sympathetic skin responses, and silastic sweat imprints are tests of sympathetic cholinergic sudomotor function.

The QSART measures axon reflex-mediated sudomotor responses quantitatively and evaluates post-ganglionic sudomotor function. Recording is usually carried out from the forearm and three lower extremity skin sites to assess the distribution of post-ganglionic deficits.

The TST evaluates the distribution of sweating by a change in color of an indicator powder. This test has a high sensitivity, and its specificity for delineating the site of lesion is greatly enhanced when used in conjunction with QSART.

Sweat imprints are formed by the secretion of active sweat glands into a plastic (silastic) imprint. The test can determine sweat gland density, a histogram of sweat droplet size and sweat volume per area.

Sensory neuropathy

Care of diabetic neuropathy in the feet and elsewhere is very important. Routine Electrodiagnostic testing (EDX) studies are not required simply by the presence of diabetes. Unlike hemoglobin A1c testing or retinal testing, similar periodic EDX testing is not established in well-recognized national protocols for effective diabetic care. The value of incidental EDX testing or tracking in diabetics, including those with loss of sensation, has not been established to improve health outcomes over careful neurologic physical exam testing. EDX testing is appropriate for specific, complex clinical situations where diabetic neuropathy and entrapment or neurologic diagnoses must be further investigated. Examples include investigation of lumbar radiculopathies, carpal entrapment, and diagnostic differentials established by a detailed physical exam and history. While EDX studies have been used in Phase III clinical trials to test drug effectiveness, no current diabetic neuropathy drugs have FDA requirements for EDX monitoring during their use. Medicare’s benefits for routine foot care in diabetics or other neuropathic patients do not require EDX testing before coverage, but are fulfilled by physical exam testing for loss of protective sensation. Refer to National Coverage Determination (NCD) 70.2.1 for diabetic peripheral neuropathy diagnosis with loss of protective sensation listed in the National Coverage section of the policy.


Most autonomic disorders are diagnosed clinically, with laboratory and formal diagnostic testing playing an adjunctive or confirmatory role. Testing may also be appropriate to monitor disease progression when there is a change in clinical status, or to evaluate a patient’s response to specific treatment for an autonomic disorder.

Autonomic function testing is covered as reasonable and necessary when used as a diagnostic tool to evaluate symptoms indicative of vasomotor instability, such as hypotension, orthostatic tachycardia, and hyperhidrosis after more common causes have been excluded by other testing, and the ANS testing is directed at establishing a more accurate or definitive diagnosis or contributing to clinically useful and relevant medical decision making for one of the following indications:

  1. To diagnose the presence of autonomic neuropathy in a patient with signs or symptoms suggesting a progressive autonomic neuropathy.
  2. To evaluate the severity and distribution of a diagnosed progressive autonomic neuropathy.
  3. To differentiate the diagnosis between certain complicated variants of syncope from other causes of loss of consciousness.
  4. To evaluate inadequate response to beta blockade in vasodepressor syncope.
  5. To evaluate distressing symptoms in a patient with a clinical picture suspicious for distal small fiber neuropathy in order to diagnose the condition.
  6. To differentiate the cause of postural tachycardia syndrome.
  7. To evaluate change in type, distribution or severity of autonomic deficits in patients with autonomic failure.
  8. To evaluate the response to treatment in patients with autonomic failure who demonstrate a change in clinical exam.
  9. To diagnose axonal neuropathy or suspected autonomic neuropathy in the symptomatic patient.
  10. To evaluate and treat patients with recurrent unexplained syncope to demonstrate autonomic failure, after more common causes have been excluded by other standard testing.


Syndromes of autonomic dysfunction for which ANS might add valuable clinical information are relatively rare. Generally, only after excluding more common causes of autonomic signs or symptoms (e.g., hypotension, hyperhidrosis, and orthostatic tachycardia) may formal autonomic testing be indicated to exclude or confirm rarer autonomic disorders. The following indications are considered NOT medically reasonable and necessary and will not be covered:

  1. Patient screenings without signs or symptoms of autonomic dysfunction, including patients with diabetes, hepatic or renal disease.
  2. Testing for the sole purpose of monitoring disease intensity or treatment efficacy in diabetes, hepatic or renal disease.
  3. Testing where the results are not used in clinical decision-making and patient management.
  4. Autonomic Disorders is a medical subspecialty defined by competence in: (1) understanding of the health and disease of the autonomic nervous system (ANS); (2) performance and interpretation of clinical and laboratory evaluation of ANS; and (3) diagnosis and care of those who suffer from autonomic dysfunctions. All practitioners performing ANS should meet criteria for eligibility of certification in Autonomic Disorders as recognized by the United Council of Neurologic Subspecialties (UCNS) or such similar organization established by the American Board of Podiatric Medicine. The American Board of Podiatric Medicine shall follow the training requirements and core curriculum requirement established by the UCNS for its Autonomic Disorders Accreditation. Pathways of determining eligibility as outlined by the UCNS including: the applicants must have completed one of two eligibility pathways. The pathways are: 1. Fellowship and 2. Practice Track meeting the criteria as so outlined in one of the pathways substituting only the podiatric medical education requirements certification instead of the AMA/AOA CME requirements.
  5. General professional standards with FDA clearance apply to all equipment used in ANS testing.
  6. Testing with ANSAR ANX 3.0 or other similar machine is considered investigational or for screening and will not be covered.
  7. According to a report from Casellini1, use of an apparatus for testing electrochemical skin conductance (ESC) that "consist of two sets of large-area stainless steel electrodes for the hands and feet that are connected to a computer for recording and data-management purposes. The electrodes are alternately used as an anode or cathode, and a direct current incremental voltage of less than or equal to 4 V is applied to the anode. Through reverse iontophoresis, the device generates voltage to the cathode and a current (intensity of around 0.2 mA) between the anode and cathode proportional to chloride concentration. At low voltages (less than 10 V), the stratum corneum is electrically insulating, and only sweat-gland ducts are conductive [in theory]." The report continues saying the (ESC) "expressed in microSiemens (µS), is the ratio between the current generated and the constant DC stimulus (less than or equal to 4 V) applied to the electrodes. … During the test, patients were required to place their hands and feet on the electrodes and to stand still for 2–3 min. The device produces ESC results for individual right and left hands and feet. It then calculates an average score between right and left hands and feet. All the ESC results [presented in this study] correspond to the average ESC between right and left sides for both hands and feet. … Neither special subject preparation nor specially trained medical personnel are required."

    This apparatus and other similar devices do not meet the same specification for sudomotor testing. Please refer to Billing and Coding Article: Autonomic Function Tests, A54954, for correct coding and billing information related to this particular and similar apparatuses. Most references do not show clear indication of clinical utility for this type of device and were performed primarily as screening tests for diabetic peripheral neuropathy.

    As technology continues to improve and the continuing automation takes over more and more of the performance of the test, the need for additional coding will be obvious to describe these new technologies.
  8. AFT shall not be used as a test for the diagnosis of a peripheral polyneuropathy of diabetes nor for monitoring of the diabetic patient with peripheral neuropathy.
  9. Combined parasympathetic and sympathetic adrenergic function testing with at least 5 minutes of passive tilt does not include beat-to-beat recording and represents a duplication of the services represented by cardiovagal innervation and vasomotor adrenergic innervation. Therefore, Novitas does not consider combined parasympathetic and sympathetic adrenergic function testing to be reasonable and necessary if performed with cardiovagal innervation and vasomotor adrenergic innervation in that this would represent a duplication of services. Combined parasympathetic and sympathetic adrenergic function testing should include beat-to-beat evaluation of response to deep breathing. Providers should refer to the applicable Current Procedural Terminology (CPT) Manual to assist with proper reporting of autonomic function testing.
  10. It is expected that parasympathetic and sympathetic heart rate testing would be a component of an initial neurologic assessment. Therefore, it would not be considered a significant, separately identifiable service when performed on the same day as an Evaluation and Management (E/M) service performed to evaluate signs and symptoms of possible autonomic dysfunction.

Equipment for Autonomic Nervous System Studies

Equipment with FDA clearance for heart rate variability measurements in response to paced respirations and exercises that tests only heart rate variability does not meet the full range of testing parameters required for the performance of cardiovagal innervation and vasomotor adrenergic innervation testing, and does not ensure full test requirements, such as blood pressure monitoring and blood oxygen levels; nor do they incorporate proper testing conditions, such as the use of a tilt table. Providers may be asked to supply information on the equipment used to perform autonomic nervous system studies, to ensure that all studies performed meet the requirements of the procedure.

The redetermination process may be utilized for consideration of services performed outside of the reasonable and necessary requirements in this LCD.

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