Modifier 90 | Reference (Outside) Laboratory Explained

Modifier 90 describes a reference (outside) laboratory and indicates that an outside lab performed a laboratory or pathology test instead of the treating or reporting provider.

1. What is modifier 90?

Modifier 90 is a billing modifier that indicates that an outside lab performed a laboratory or pathology test instead of the treating or reporting provider.

It is used to bill the patient’s insurance for the lab code with modifier 90. Physicians would need to pay the lab separately for their services since the lab would not bill the patient’s insurance.

2. When to use modifier 90?

Modifier 90 is appropriate when reference or outside the laboratory performs the test instead of the treating or reporting provider. Independent labs should use the modifier when sending specific tests to a reference lab. However, Medicare and most payers restrict the appropriate use of this modifier.

3. Description

The official description of modifier 90 is “reference (outside) laboratory”.

4. Examples

Procedures requiring modifier 90 include genetic testing, specialized blood tests, and complex pathology tests.

5. Documentation

To use modifier 90, the referring and reference laboratories’ names, addresses, and CLIA numbers must be included on the Medicare claims.

Proper documentation is necessary to ensure the claim is paid at the rate used for the reference lab’s jurisdiction.

6. Billing

To bill for services using modifier 90, physicians and other providers must collect specimens for lab tests and then send the specimens to an outside lab for testing.

They can then bill the patient’s insurance for the lab code with modifier 90 appended. Physicians would need to pay the lab separately for their services since the lab would not bill the patient’s insurance.

7. Common mistakes

Medical coders make common mistakes when using modifier 90, including misusing it or failing to include the necessary documentation.

To avoid these mistakes, coders should ensure that they understand the appropriate use of the modifier and follow the necessary documentation requirements.

8. Other modifiers related to modifier 90

Other modifiers related to modifier 90 include modifier 91, which is used to indicate a repeat clinical diagnostic laboratory test, and modifier 92, which is used to indicate a laboratory test performed outside the usual laboratory.

9. Tips

When using modifier 90, it is essential to ensure the necessary documentation is included and the modifier is used appropriately. Coders should also be aware of other modifiers related to modifier 90 and how they are used.