Effective for dates of service on or after May 1, 2010, CPT code 83518 (immunoassay for analyte other than infectious agent antibody or infectious agent antigen, qualitative or semiquantitative; single step method [eg, reagent strip]) is no longer considered a Clinical Laboratory Improvement Amendments (CLIA)-waived test. Therefore, providers can no longer bill code 83518 with a QW modifier (a kit is being used).