Q&A: Choosing therapeutic drug monitoring or colonoscopy as principal

Q: I’m working on a case where a patient with atrial and mitral prosthetic heart valves on warfarin is being admitted for a heparin drip bridge prior to a colonoscopy. I’m having some trouble determining the principal diagnosis. The encounter is for heparin bridge and the closest code I can find is Z51.81, Encounter for therapeutic drug level monitoring. Is that an appropriate principal diagnosis? The other option would be Z12.11, Encounter for screening for malignant neoplasm of colon).

A: The last time this was addressed was in Coding Clinic, Third Quarter, 2002, p. 14 (emphasis added):

Question: A patient is admitted with severe dental caries and periodontal disease. She has been on Coumadin in the past for clotting of her dialysis access. This had to be stopped prior to her dental procedure and she needed to be switched to IV Heparin. The documentation states that the patient was admitted for anticoagulant adjustment prior to her surgery.

In addition, the history of present illness specifies, "the primary reason for admission is not for her teeth extraction but because she has had chronic clotting problems of her vascular access for dialysis. Every time her Coumadin is stopped, the patient's access clots." It appears that the dental extraction would have been carried out as an outpatient if the patient had not had clotting problems. What should be the principal diagnosis in this case? The dental condition or V58.61 or V07.8?

Answer: Assign code 521.09, Other dental caries, as the principal diagnosis. The dental condition required care, and the patient's medications had to be adjusted in preparation for the dental surgery. Code 523.9, Unspecified gingival and periodontal disease, code V58.83, Encounter for therapeutic drug monitoring, and code V58.61, Long-term (current) use of anticoagulants, should be assigned as secondary diagnoses.

Applying the rationale from Coding Clinic above, the reason for admission would be the condition for which the colonoscopy is being done. You would also add the Z79.82 code for long term (current) use of antithrombotic/antiplatelet. If this truly is a screening colonoscopy, then the Z12.11 could be the principal diagnosis. This seems appropriate to me over Z51.81 as drug monitoring is not the goal of the episode of care, but rather a necessary step in order to accomplish the colonoscopy. In other words, they are not bringing in the patient with the sole objective of monitoring and bridging anticoagulation therapy; the objective is the colonoscopy. You should also use an additional code to identify any pervious personal history or family history of neoplasms and or GI issues which might support the screening colonoscopy.

Remember, though, that these types of questions are generally best left to your coders. Regardless of my answer, how the coder interprets the record will supersede anything you or I can come up with, and that code assignment is somewhat subject to change based on the subjective tone and terms used by the physician in the admission note. Be that as it may, I tried to come up with a possible code here just for informational sake.

One last point. Submitting these codes as highlighted in the Official Guidelines may very well generate denial questions as the insurance company may have specifically stipulated they do not cover certain admissions reported with specific ICD-10 codes. If this happens, you will have to work within the payer contract and directly with the payer in order to determine how the reporting they require differs from that stated in the Official Guidelines. I would like to say that sort of analysis may also need to occur for Medicare cases where following guidelines might actually create a recovery audit denial but unfortunately when it comes to CMS, the Official Guidelines have to be followed exactly—no exceptions. This means you may find yourself on the losing end of an appeal in such circumstances.

Editor’s note: Allen Frady, RN, BSN, CCDS, CCS, CRC, CDI education specialist for BLR Healthcare in Middleton, Massachusetts, answered this question. Contact him at AFrady@hcpro.com. For information regarding CDI Boot Camps visit http://hcmarketplace.com/clinical-doc-improvement-boot-camp-1.