Here's medical coding guidance on proper use of the -QW modifier from coding expert Betsy Nicoletti.
Question: I added the –QW modifier to a lab test that was CLIA-waived but did not have the –QW listed on the CLIA list. If you double-check the CLIA list, some CPT codes have –QW and some do not. Those that do not have the –QW do not require it when filing. We received denials for invalid modifier and I was required to remove the –QW from those codes I had previously added it to because I thought if a lab test was waived it required the –QW. Does that seem right?
Answer: We checked in with coding expert Betsy Nicoletti, who offered this further explanation:
“Many tests, such as measuring a patient’s glucose, have many ways to perform them - quantitative, qualitative, via an assay, via a culture, via a test kit that changes colors. Tests that may be performed via test kit - which do not require a lab tech’s clinical skill, etc. - can be performed in the office and are placed on the CLIA-waived list. It is important to check the list and make sure that the exact test for glucose that you are performing is on the list, and that you are using the correct CPT code for that test. You don’t want to use the code for “strep test done by culture” without the –QW modifier (and get paid for that service) when you have performed the quick strep test done by kit (87880), which is on the CLIA-waived list. In this case, do two things:
1. Check the CLIA-waived test list and make sure the test/manufacturer is on the list.
2. Check the CPT book and make sure that you select the correct CPT code for that test.”