The KX modifier is probably correct, it is stating you have appropriate documentation on file to support the medical necessity for the DME product. KX modifier indicates that the provider has written this order, it was used to order the equipment/drugs/supplies needed to treat the patient. This order must be kept on file by the supplier and made available to the carrier on request. This should indicate the diagnosis/reason for the equipment/medication and the date, the provider's signature as with any other order.
I also found this: KX: SPECIFIC REQUIRED DOCUMENTATION ON FILE. (EFFECTIVE DATE 7/1/2002)This modifier may be used to indicate that specific required documentation is on file in the patient's medical record. Documentation must be submitted upon request. Applicable policies include: Manual and power mobility bases and accessories, Glucose monitors & supplies, PAP devices and accessories, Respiratory Assist Devices (RAD), Commodes, Hospital beds and accessories, Therapeutic Shoes for Diabetics, Heavy duty walkers, Urological Supplies, Epoetin, Support surfaces - Groups 1, 2, and 3, Refractive Lenses - Anti reflective coating, tint, and oversize lenses, polycarbonate lenses, Cervical Traction devices - Codes E0849 and E0855, External infusion (insulin) pumps, High Frequency chest wall oscillation devices, Nebulizers (Brovana or Perforomist) - J7605 and J7606, Negative Pressure Wound Therapy, Patient lifts - E0636 and E1035, Speech generating devices, Wheelchair seating, Orthopedic Footwear, Home Dialysis supplies, Oral Antiemetic - J8502 and J8540.
I hope this helps!!