Payers not following coding clinic?

Our facility has been receiving an increase in DRG downgrades recommending deletion of the code P9683 meconium staining. We appealed these downgrades by citing AHA Coding Clinic, fourth quarter 2013 pg. 95 Effective with discharges: October 21, 2013. The response I received from the payer who upheld one of these downgrades stated the following:

"... this is not a traditional DRG coding audit, it is a clinical validation audit. . . . we are not only confirming the presence of meconium based on documentation, but also reviewing the overall clinical significance the presence of meconium staining had the newborn. In this case, it was acknowledged that meconium staining was present at the time of delivery. However, the infant did not display any symptomatology that would be indicative of the meconium having had any had any effect on the health and well-being of this infant upon delivery and thereafter. . . . it is their (provider) responsibility to ensure that the medical record documentation fully and completely support the diagnosis . . . "

Is it a legitimate argument on the part of the payer to disregard the coding clinic in this scenario? How do I dispute this? I have since educated the providers regarding what the rules are to capture additional conditions, but I have a problem with disregarding coding clinics. Any recommendations or education are appreciated. Thank you!