Urine drug screen

We are receiving a lot of denials from insurances that say we should be billing with a modifier for multiple units for G0431 and 80102.  What would be the appropriate modifier for a lab to use for these codes? 
Thanks in advance for your assistance. 

re: Urine drug screen

Look at: Modifier 59: Used for distinct procedural services such as multiple services submitted by a laboratory for the same member on the same day.
80102, each procedure-drug confirmation.
http://www.codemap.com/clc/clcwp.pdf
Code G0431
This code “will be used to report more complex testing methods, such as multi-channel chemistry analyzers, where a more complex instrumented device is required to perform some or all of the screening tests for the patient. Note that the descriptor has been revised for CY 2011. This code may only be reported if the drug screen test(s) is classified as CLIA high complexity test(s) with the following restrictions:
“G0431 may only be reported when tests are performed using instrumented systems (i.e., durable systems capable of withstanding repeated use).
“CLIA waived tests and comparable non-waived tests may not be reported under test code G0431; they must be reported under test code G0434.
“CLIA moderate complexity tests should be reported under test code G0434 with one (1) Unit of Service (UOS).
“G0431 may only be reported once per patient encounter.
“Laboratories billing G0431 must not append the QW modifier to claim lines.”
http://www.medac.com/index.php/news-a-events/billing-a-compliance-alerts/231-cms-clarifies-drug-screen-codes