Pathology/Lab Coding Alert

Applying the correct code is as easy as understanding the test's purpose.

Drug testing makes up a significant proportion of the activity in your lab. But coding it doesn’t have to take up a lot of your time. Simply put, if you know the differences between the purposes of the testing, then you can correctly assign the code for it.

So, let’s put the first pieces of the drug testing puzzle together by looking at the relevant CPT^® and HCPCS codes for the different kinds of tests.

Know the Difference Between Presumptive, Definitive, and Therapeutic Testing

Selecting the correct code for drug testing begins with your ability to understand the test’s purpose, as CPT^® codes are divided into groups based on that information.

Presumptive drug tests determine the presence or absence of drugs or drug class(es) without prior knowledge of the drug. In other words, a presumptive test is a screen to determine whether a drug is, or is not, present in the patient’s system.

Definitive drug testing is a separate procedure that often occurs after a presumptive test comes back positive. Its purpose is to quantify the amount of an identified drug in the patent’s system.

Therapeutic drug testing is a form of definitive drug testing, but the drug in question is a known medicine that a provider has prescribed to the patient. The purpose of this kind of test is to help a provider evaluate the drug for its therapeutic effect on the patient at the level prescribed and/or to monitor for possible drug interactions or even toxicity.

Know These Presumptive Drug Test Codes

CPT^® provides three codes to describe presumptive testing based on the testing method used. You should report just one of the following codes once per day regardless of the number of drugs or drug classes involved in the screening:

• 80305 (Drug test(s), presumptive, any number of drug classes, any number of devices or procedures; capable of being read by direct optical observation only (eg, utilizing immunoassay [eg, dipsticks, cups, cards, or cartridges]), includes sample validation when performed, per date of service)
• 80306 (... read by instrument assisted direct optical observation (eg, utilizing immunoassay [eg, dipsticks, cups, cards, or cartridges]), includes sample validation when performed, per date of service)
• 80307 (… by instrument chemistry analyzers (eg, utilizing immunoassay [eg, EIA, ELISA, EMIT, FPIA, IA, KIMS, RIA]), chromatography (eg, GC, HPLC), and mass spectrometry either with or without chromatography, (eg, DART, DESI, GC-MS, GC-MS/MS, LC-MS, LC-MS/MS, LDTD, MALDI, TOF) includes sample validation when performed, per date of service)

For these tests, the lab will generally report findings as either above a specified threshold (positive) or below (negative). A negative test does not mean the patient is completely free of the drug; it simply means the level of the drug in the patient’s system is below the threshold established.

Depend on This Definitive Drug Test Advice

CPT^® tells you definitive drug tests can be found in the 80320 (Alcohols) to 80373 (Tramadol) range. The codes are broken down by drug classes, not individual drugs. Some of the analytes have multiple codes associated with them.

To use the codes correctly, you should first consult the Definitive Drug Classes Listing table in the CPT^® code book and match the drug with the appropriate code class and the corresponding code. For example, suppose a patient is being tested for opioid and opiate analogs. In this case, you’ll use have a choice of three codes:

• 80362 (Opioids and opiate analogs; 1 or 2)
• 80363 (… 3 or 4)
• 80364 (… 5 or more)

In this situation, you’ll choose the code that corresponds with the number of drugs the patient has tested positive for. If the patient tests positive for three of the drugs in the drug class, for example, you’ll use 80363.

Be careful: The list of drugs in the Definitive Drug Classes Listing table is not comprehensive. But you can locate an analyte subject to a definitive drug procedure in one of several ways:

• Follow CPT^® instructions and check to see if the drug is listed in the Therapeutic Drug Assay codes (80143-80203).
• Follow CPT^® instructions and check to see if the drug is listed in the Chemistry (82009-84830) section.
• Consult the drug classification directory published by the Food and Drug Administration (FDA). Here, for example, you will find buprenorphine classified as a partial opioid agonist, which correspond to CPT^®’s opioids and opiate analog classification reportable to testing codes 80363-80364
• Use one of the not otherwise specified (NOS) definitive drug test codes:
  • 80375 (Drug(s) or substance(s), definitive, qualitative or quantitative, not otherwise specified; 1-3)
  • 80376 (… 4-6)
  • 80377 (… 7 or more)

Understand When to Use 80374

One last definitive drug test code, 80374 (Stereoisomer (enantiomer) analysis, single drug class), is reserved for testing drugs commonly used for pain management, substance disorder treatment, and similar therapeutic purposes. The drugs can be legitimately manufactured, but they can also be illicitly produced. The test enables the provider to determine which is the case by analyzing chemical components, called isomers, in the drug being tested.

Take on These Therapeutic Drug Test Codes and Advice

Like the definitive drug test codes, CPT^® also provides codes for therapeutic drug tests listed alphabetically in the range 80143 (Acetaminophen) to 80203 (Zonisamide), plus code 80299 (Quantitation of therapeutic drug, not elsewhere specified). 

Remember: You’ll only use one of these codes when a clinician has prescribed a drug for a patient and is evaluating the patient’s response to the drug, the dosage being prescribed, or any adverse reactions. If the clinician has not prescribed the drug and the patient is abusing a drug, you’ll need to turn to a definitive drug test code, even if the drug is listed in the Therapeutic Drug Assay section.

And Note the Medicare Exception

For Medicare beneficiaries, you’ll use one of the following:

• G0480 (Drug test(s), definitive, utilizing (1) drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers) … (2) stable isotope or other universally recognized internal standards in all samples …  and (3) method or drug-specific calibration and matrix-matched quality control material … qualitative or quantitative, all sources, includes specimen validity testing, per day; 1-7 drug class(es), including metabolite(s) if performed)
• G0481 (... 8-14 drug class(es), including metabolite(s) if performed)
• G0482 (... 15-21 drug class(es), including metabolite(s) if performed)
• G0483 (... 22 or more drug class(es), including metabolite(s) if performed)
• G0659 (Drug test(s), definitive, utilizing drug identification methods able to identify individual drugs and distinguish between structural isomers (but not necessarily stereoisomers) … qualitative or quantitative, all sources, includes specimen validity testing, per day, any number of drug classes).

Fortunately, Medicare does not distinguish between presumptive and therapeutic tests; it simply differentiates between testing methodologies and number of drug classes tested for correct code choice.

Stay tuned for the second part of this series, in which we’ll look at the correct diagnosis coding to prove medical necessity for drug testing.

Bruce Pegg, BA, MA, CPC, CFPC, Managing Editor, AAPC