Revenue Cycle Insider

Make sure you answer the mini quiz at the end.

Last month, we looked at the difference between presumptive, definitive, and therapeutic drug testing, and the correct way to code for each type of test. Now, in the second part of the series, we turn our attention to the diagnosis codes used to demonstrate medical necessity for these tests. And, to see if you’ve been paying attention, we’ve added a couple of test-yourself questions for you to answer.

Check Out This LCD for Presumptive Drug Test Necessity

A good place to find diagnosis codes that justify presumptive/definitive drug tests is the Medicare local coverage determination (LCD) >A56818 (Billing and Coding: Urine Drug Testing). The document provides an exhaustive list of ICD-10-CM codes that justify orders for CPT^Ò presumptive drug test codes 80305-80307 (Drug test(s), presumptive…) and HCPCS codes G0480-G0483 and G0659 (Drug test(s), definitive …). 

Unsurprisingly, the list includes numerous drug abuse codes from the F10-F19 (Mental and behavioral disorders due to psychoactive substance use) group as well as codes from the T36-T50 (Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances) and T51-T65 (Toxic effects of substances chiefly nonmedicinal as to source) code sets.

The list also contains a number of encounter (Z) codes that the ordering clinician may use. More on them in a moment.

Understand T36-T65 Codes and the Table of Drugs and Chemicals

Another tool that helps you determine the intent of the lab ordered by a clinician is the ICD-10-CM Table of Drugs and Chemicals. This lists the codes in categories T36-T65, which are combination codes identifying the substance the patient took as well as the intent behind the ingestion of the substance. In addition to being broken down by substance type (indicated by the 4^th character), the codes are also broken down by the intent behind the adverse effect:

Poisoning means a negative reaction to the use of a medication. ICD-10-CM distinguishes these different types of poisoning:

• Accidental or unintentional poisoning, indicated by 5^th or 6^th character 1. This category includes poisoning resulting from an error in the drug prescription or from a provider’s or another’s improper administration of a drug to the patient.
• Intentional poisoning, or the intent to cause self-harm, indicated by 5^th or 6^th character 2. This category includes intentional overdosing on the part of the patient.
• Poisoning by another, or assault, indicated by 5^th or 6^th character 3.
• Undetermined poisoning, indicated by 5^th or 6^th character 4.

Toxic effect means the ingestion of, or contact with, a harmful substance that is generally not medicinal in nature, such as alcohol, recreational drugs, and substances that are not meant for ingestion, such as insecticides.

For therapeutic drugs, ICD-10-CM lists two other negative reactions that can be coded with a code from T36-T50:

• Adverse effect means a problem that arises after taking a drug that has been correctly prescribed and properly administered, indicated by 5^th or 6^th character 5.
• Underdosing: means taking less of a medication than is prescribed, indicated by 5^th or 6^th character 6. In situations such as this, you’ll see ICD-10-CM noncompliance (Z91.12-, Z91.13-) or complication of care (Y63.6-Y63.9) codes.

For further clarification of the ICD-10-CM definitions of these terms, make sure you consult official guideline I.C.19.e “Adverse Effects, Poisoning, Underdosing and Toxic Effects.”

And Understand These Z Codes Nuances

For therapeutic drug monitoring lab orders, you’ll frequently see Z51.81 (Encounter for therapeutic drug level monitoring). But it’s important this code is accompanied by a code from Z79.- (Long term (current) drug therapy) to pinpoint the specific type of therapeutic drug the clinician is monitoring. Even so, per guideline I.21.c.7, remember that a code from Z51.- can be used as a first-listed code.

Also, if the ordering clinician uses a patient or caregiver noncompliance code, make sure the order follows ICD-10-CM Code also instructions that accompany Z91.1.- (Patient’s noncompliance with medical treatment and regimen) and Z91.A- (Caregiver’s noncompliance with patient's medical treatment and regimen). These tell you to add a code from T36-T50 as applicable for many of the codes.

Putting it all Together

Test Yourself 1: Your lab receives an order from a clinician for a test on the serum level of methotrexate using two diagnosis codes: Z79.631 (Long term (current) use of antimetabolite agent) and T45.1X5- (Adverse effect of antineoplastic and immunosuppressive drugs).

As this order is for testing on a therapeutic drug, and as the drug is a prescribed drug and the test is to measure the negative effects on the patient when the drug has been prescribed and administered correctly, you’ll turn to the definitive drug test code range 80320-80373. There, you will find 80204 (Methotrexate), which is the code you will use to report the drug assay test. For Medicare patients, Medicare may require G0480 (Drug test(s), definitive, … 1-7 drug class(es), including metabolite(s) if performed).

Test Yourself 2: A clinician prescribes morphine to a patient recovering from a back injury, and the patient returns to the clinician’s office requesting a continuation of the prescription. As the patient has a past history of cocaine use, and following state guidelines, the clinician orders your lab to perform a drug test using Z79.891 (Long term (current) use of opiate analgesic) and F14.11 (Cocaine abuse, in remission).

In this situation, as the clinician is requesting a presumptive drug test, you’ll use a presumptive drug code, most likely 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), Again, Medicare may require G0480 if the patient is a Medicare enrollee.

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