The following information is provided as clarification on how to bill the Drug Screen Testing codes. G0431 Drug screen, qualitative; multiple drug classes by high complexity test method (e.g. immunoassay, enzyme assay), per patient encounter Effective 01/01/2010 G0431 QW Effective 01/01/10-03/31/11 G0434 Drug screen, other than chromatographic; any number of drug classes, by CLIA waived test or moderate complexity test, per patient encounter Effective 01/01/2011 G0434 QW Effective 04/01/2011 A lab with a CLIA certification type 2 can perform CLIA waived tests only. A lab with a CLIA certification type 4 can perform CLIA waived and Provider Performed Microscopy Procedures (PPMPs) only. Providers with CLIA Certification Type 2 or 4 must submit G0431 QW for dates of service from January 1, 2010 through March 31, 2011 only. Providers must submit G0434 QW for dates of service on and after April 1, 2011. If you submitted G0434 or G0434 QW with dates of service 01/01/11 through 03/31/11, request a reopening for the claims to change the procedure code to G0431 QW.