CPT® Code 80161

Official Description

Carbamazepine; -10,11-epoxide

Common Language Description

The CPT® Code 80161 refers to a laboratory test specifically designed to monitor the therapeutic levels of carbamazepine-10,11-epoxide (CBZ10-11), which is the active metabolite of the anticonvulsant medication carbamazepine (CBZ). Carbamazepine is utilized primarily for the treatment of epilepsy and certain mood disorders, but it possesses neurotoxic properties that necessitate careful monitoring of its levels in the bloodstream. The test is crucial for assessing the potential for toxicity, which can arise from an overdose of carbamazepine. Symptoms of toxicity include serious conditions such as arrhythmias, hypotension, respiratory depression, seizures, and even coma. The therapeutic range for total carbamazepine serum levels is established between 4.0 to 12.0 mcg/mL, while levels reaching 15.0 mcg/mL are considered critical and indicative of toxicity. Additionally, when the serum concentration of the metabolite exceeds 40% of the parent drug, there is a similar risk of toxicity. For the metabolite carbamazepine-10,11-epoxide, the clinically acceptable serum concentration range is defined as 0.4 to 4.0 mcg/mL, with concentrations equal to or greater than 8.0 mcg/mL classified as toxic. To conduct this test, a blood sample is drawn approximately 12 hours after the patient's last dose of carbamazepine. The sample is then analyzed using high-performance liquid chromatography (HPLC), a precise method for separating and quantifying compounds in a mixture. Monitoring the levels of the active metabolite is essential, as patients may present with total serum concentrations of carbamazepine that fall within the therapeutic range, yet still produce significant levels of its active metabolite, thereby increasing the risk of dangerous toxicity.

1. Indications

The laboratory test associated with CPT® Code 80161 is indicated for the following conditions:

Monitoring Therapeutic Levels This test is performed to monitor the therapeutic levels of carbamazepine-10,11-epoxide, ensuring that the patient remains within the safe and effective range of medication.
Assessment of Toxicity Risk It is utilized to assess the risk of toxicity in patients who may have overdosed on carbamazepine, as toxicity can lead to severe clinical manifestations.
Evaluation of Active Metabolite Levels The test is important for evaluating the levels of the active metabolite, especially when total serum concentrations of carbamazepine are within therapeutic limits but may still pose a risk due to elevated metabolite levels.

2. Procedure

The procedure for conducting the test associated with CPT® Code 80161 involves several key steps:

Step 1: Patient Preparation Prior to the blood draw, the patient should be informed about the test and the importance of timing, specifically that the blood sample should be collected approximately 12 hours after the last dose of carbamazepine. This timing is critical to obtaining accurate serum levels of the active metabolite.
Step 2: Blood Sample Collection A qualified healthcare professional will draw a blood sample from the patient, typically from a vein in the arm. The sample must be collected in a suitable container that is appropriate for serum testing.
Step 3: Laboratory Analysis The collected blood sample is sent to a laboratory where it is processed. The serum is separated from the blood cells, and high-performance liquid chromatography (HPLC) is employed to analyze the sample. This method allows for precise measurement of the carbamazepine-10,11-epoxide levels in the serum.
Step 4: Interpretation of Results Once the analysis is complete, the laboratory will provide the results, indicating the concentration of carbamazepine-10,11-epoxide. These results are then interpreted by the healthcare provider to determine if the levels are within the therapeutic range or if there is a risk of toxicity.

3. Post-Procedure

After the procedure, the patient may be advised to continue monitoring their symptoms and report any adverse effects or signs of toxicity to their healthcare provider. It is essential for the provider to review the test results in conjunction with the patient's clinical presentation and medication regimen. If the levels of carbamazepine-10,11-epoxide are found to be elevated, the healthcare provider may need to adjust the dosage of carbamazepine or consider alternative treatment options to mitigate the risk of toxicity. Regular follow-up testing may also be recommended to ensure that the patient remains within the therapeutic range and to monitor for any changes in their condition.

Short Descr	ASY CARBAMAZEPIN 10,11-EPXID
Medium Descr	DRUG ASSAY CARBAMAZEPINE -10,11-EPOXIDE
Long Descr	Carbamazepine; -10,11-epoxide
Status Code	Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days	XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC)	9 - Not Applicable
Multiple Procedures (51)	9 - Concept does not apply.
Bilateral Surgery (50)	9 - Concept does not apply.
Physician Supervisions	09 - Concept does not apply.
Assistant Surgeon (80, 82)	9 - Concept does not apply.
Co-Surgeons (62)	9 - Concept does not apply.
Team Surgery (66)	9 - Concept does not apply.
Diagnostic Imaging Family	99 - Concept Does Not Apply
CLIA Waived (QW)	No
APC Status Indicator	Conditionally packaged laboratory tests
Type of Service (TOS)	5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS)	none
MUE	1

90	Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.
59	Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25.
91	Repeat clinical diagnostic laboratory test: in the course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of modifier 91. note: this modifier may not be used when tests are rerun to confirm initial results; due to testing problems with specimens or equipment; or for any other reason when a normal, one-time, reportable result is all that is required. this modifier may not be used when other code(s) describe a series of test results (eg, glucose tolerance tests, evocative/suppression testing). this modifier may only be used for laboratory test(s) performed more than once on the same day on the same patient.