Q&A: Assigning a principal diagnosis

Q: When a patient comes in with two diagnoses and the documentation reflects that either could be the principal diagnosis, do we choose the principal as the diagnosis that is being treated more intensely, or do we choose the higher paying DRG? Is it true that when a patient comes in with two diagnoses with both being treated equally, you can choose either as the principal diagnosis? In a case where one diagnosis is being treated more intensely, however, do you choose that one even though it is a lower weighted DRG? I usually choose the one that is being treated more intensely even though it might be lower weighted.

A: I am in 100% agreement with you. Everyone must go with the culture of their employer but speaking of CDI as an industry, it is unwise in my opinion for a CDI department to be driven by financial outcomes when determining which diagnoses should be principal in the scenario you outlined. I always go by the old motto of "doing the right thing for the right reasons" because good only follows that premise. Having said that, there will be times when the diagnosis with the highest relative weight is going to be the principal diagnosis between multiple diagnoses; however, resource consumption should be equal in those cases and follow-up will be needed to determine if the principal diagnosis has been denied by the payer.

As a former auditor, I would deny cases I saw where the ONLY determining factor for principal diagnosis selection was relative weight and resource consumption was heavier on another diagnoses. I would weigh the resource consumption for all of the diagnoses and make my determination accordingly. I have created two patient scenarios for you to compare.

Scenario #1:

A patient presents with a chief complaint of shortness of breath (SOB). A hospitalist is the attending on this case. This patient is admitted to a medical-surgical unit.

The patient has a past medical history of atrial fibrillation (A fib) on coumadin and hypertension (HTN).

• Vital signs upon arrival:
  • Heart rate (HR): 150
  • Respiratory rate (RR): 28
  • Blood pressure (BP): 160/95
  • Oxygen saturations: 93% on room air
• EKG reveals A fib with rapid ventricular response (RVR) with a rate of 153.
• Chest x-ray reveals cardiomegaly and vascular congestion with atelectasis.
• The emergency department physician documents the following: Patient presents with worsening SOB over two days. Dyspnea noted on exertion and patient can speak in full sentences at this time. Patient reports no history of congestive heart failure (CHF).
• Physical Exam: Audible wheezing with rales in the left lower lobe. Pitting edema 2+ in bilateral ankles. Tachypneic.
• Repeat chest x-ray: Cardiomegaly, vascular congestion, and bilateral atelectasis. Possible pulmonary edema noted.
• Labs: Brain natriuretic peptide (BNP) is drawn and result at 592.
• Treatment: 2L oxygen via nasal cannula is applied with saturation at 96%. Foley is inserted and 40mg IV Lasix is given. Metoprolol 10mg IV x 1 dose is given. The patient is admitted for acute onset CHF and A fib RVR.
• The patient demonstrates 1L UOP s/p diuretic, HR has converted to sinus rhythm with a rate in the low- to mid-90s. The patient is receiving continuous telemetry. The patient continues on 2L oxygen with lowest saturation of 93%.
• ECHO ordered and demonstrated moderate right atrial and ventricular hypertrophy, ejection fraction (EF) at 55%, mitral regurgitation (MR) +2, left ventricular hypertrophy (LVH).
• Cardiac consult ordered. A fib RVR and acute diastolic CHF, new onset, are documented. A repeat chest x-ray showing an improvement in vascular congestion without pulmonary edema on repeat film. The patient is weaned to room air with resolution of SOB.
• The patient does not return to A fib and is discharged on day two on a cardiac diet, Coreg 3.375mg (PO) BID, 20mg furosemide PO on prescription with a follow-up appointment for the cardiologist in two weeks.

For this scenario, I would code the principal diagnosis as the combination code for hypertensive heart disease and code the acute diastolic CHF as the MCC and then code the A fib as a secondary diagnosis (regardless of relative weights). In the tabular list for hypertensive heart disease there is an instructional note to “use additional code to identify type of heart failure.”

My rationale is that the CHF consumed most of the resources provided and the A fib resolved without return with one dose of metoprolol IV.

Scenario #2:

A patient presents with a chief complaint of SOB and chest pain. A hospitalist is the attending on this case. This patient is admitted to the ICU.

The patient has a past medical history of A fib on coumadin, HTN and chronic CHF.

• Vital signs upon arrival:
  • HR: 150
  • RR: 28
  • BP: 160/95
  • Oxygen Saturations: 93% on room air
• EKG reveals A fib RVR with a rate of 153.
• The emergency department physician documents the following: Patient presents with worsening SOB x 2 days. Dyspnea noted on exertion and patient can speak in full sentences at this time. Patient reports a history of diastolic CHF.
• Physical exam: Audible wheezing with rales in the left lower lobe. Pitting edema 2+ in bilateral ankles. Tachypneic.
• Chest x-ray: Cardiomegaly, vascular congestion, and bilateral atelectasis. Possible pulmonary edema noted. Further correlation is needed.
• Labs: BNP is drawn and results at 1200. Troponin 0.02, 0.03.
• Treatment: 2L oxygen via nasal cannula is applied with saturation at 96%. Foley is inserted and 40mg IV Lasix is given. Metoprolol 10mg IV x 1 dose is given without restoration of sinus rhythm. The patient is admitted to the intensive care unit (ICU) for A fib RVR with the need for an amiodarone drip and acute CHF exacerbation.
• The patient demonstrates 1L UOP s/p diuretic, and HR remains between 142 and 158. EKG continues to demonstrate A fib RVR on continuous telemetry. The patient continues on 2L oxygen with lowest saturation of 93%.
• Treatment: 180mg IV Amiodarone given as bolus. An IV drip of Amiodarone is initiated. The patient’s A fib RVR continues.
• Cardiac consult ordered.
• Cardiology documents a prior EF of 55% from two months prior also showing MR 2+, moderate right atrial and ventricular hypertrophy and LVH, cardiomegaly. Cardiology orders 40mg IV Lasix x 1 dose (additional dose) and begins Cardizem.
• Continuous EKG demonstrates that the patient remains in A fib RVR. 20mg Cardizem IV push is administered with the Cardizem converting the rhythm to sinus rhythm. IV drip of Amiodarone is discontinued, and an IV drip of Cardizem is initiated to titrate to a target HR of 80-90, maintaining rate at 10- 15mg/hr.
• A fib RVR refractory to amiodarone and acute diastolic CHF are diagnosed. A repeat chest x-ray showing resolution in vascular congestion without pulmonary edema on repeat film. The patient’s complaints of chest pain and SOB have resolved, and the patient is weaned to room air.
• A query was submitted asking which diagnosis was responsible for the admission and the physician’s answer was the A fib was the predominate reason for admission due to the need for rate control which contributed to the exacerbation of CHF.
• The patient is discharged on day two with a follow-up appointment with the cardiologist in one week. Electrophysiology study is ordered as an outpatient service.

In this scenario, A fib RVR consumed most of the resources resulting in an ICU bed which has an increase in nurse-to-patient ratio. The focus was predominately on resolving the A fib RVR as the patient was resistant to the initial pharmacotherapy. The onset of SOB and the need for chest x-rays can be attributable to both conditions since it appears that the A fib RVR is what precipitated the CHF exacerbation as the query answer indicated. Therefore, I would code the A fib RVR as the principal diagnosis with the combination code for the HTN and HF and the acute on chronic CHF as the MCC. Lastly, don’t forget that a query can be sent if the documentation is unclear on which diagnosis is responsible for the admission for the only person who can answer this question when it’s unclear is the provider.

Editor’s Note: Dawn Valdez, RN, LNC, CDIP, CCDS, CDI education specialist and CDI Boot Camp instructor for HCPro in Middleton, Massachusetts, answered this question. For information, contact her at dvaldez@hcpro.com. For information regarding CDI Boot Camps, click here. This article was originally published in August 2019 and has been updated according to the latest coding and documentation guidelines.