Which diagnosis is principal?

Most coders and clinical documentation improvement (CDI) specialists are familiar with the Uniform Hospital Discharge Data Set (UHDDS) definition of principal diagnosis: the condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.

That seems like a very straightforward definition on the surface, but in practice it’s not always so clear cut. Remember that the reason the patient came in is not always the same as the reason the physician admitted the patient.

The circumstances of the patient's admission into the hospital always govern the selection of principal diagnosis (scope of care, diagnostic workup, and therapy provided), says Jennifer Avery, CCS, CPC-H, CPC, CPC-I, AHIMA-approved ICD-10-CM/PCS trainer, senior coding instructor for HCPro, a division of BLR, in Danvers, Massachusetts. However, the coding conventions/guidelines for ICD-9-CM or AHA's Coding Clinic for ICD-9-CM may often provide guidance on principal diagnosis selection.

For example, a patient comes into the ED with a closed skull fracture and cerebral edema and is admitted to the hospital. Which diagnosis is principal? Either diagnosis could be the reason the patient was admitted, says Kim Carr, RHIT, CCS, CDIP, CCDS, AHIMA-approved ICD-10-CM/PCS trainer, AHIMA ICD-10 ambassador, and clinical documentation director for HRS in Baltimore.

Think about which condition is more severe, Carr says. The physician likely had to get the cerebral edema under control before performing any procedures to fix the fracture. However, coders and CDI specialists could look at it another way. Maybe the physician performed surgery on the fracture, which could make the fracture the principal diagnosis, if treating the fracture was the reason for the admission.

Coders and CDI specialists may need to query for this case and have the physician state which injury was more severe, Carr says.

Coding Clinic, First Quarter, 2010, p. 8, addressed a question related to cerebral edema due to stroke. “Cerebral edema is very tricky because as an MCC, and as a relatively high-weighted condition in APR-DRGs and MS-DRGs, there should be some clinical evidence that it’s significant,” James S. Kennedy, MD, CCS, president of CDIMD in Smyrna, Tennessee.

This Coding Clinic addressed a question regarding whether it is appropriate to code vasogenic edema when the physician documents it for a patient admitted and diagnosed with intracerebral hemorrhage.

The response indicated that it is appropriate to assign code 431 (intracerebral hemorrhage) as the principal diagnosis and code 348.5 (cerebral edema) as an additional diagnosis. But coders should be able to defend this with documentation of clinical circumstances, such as if the patient is:

• In the intensive care unit
• Intubated
• Receiving glycerol, diuretics, or high-dose steroids
• Possibly undergoing surgery

Two or more possible principal diagnoses
In some cases, two conditions could be equally responsible for the admission. ICD-9-CM Official Guidelines for Coding and Reporting specifically address this possibility. Section II.c states:

In the unusual instance when two or more diagnoses equally meet the criteria for principal diagnosis as determined by the circumstances of admission, diagnostic workup and/or therapy provided, and the Alphabetic Index, Tabular List, or another coding guidelines does not provide sequencing direction, any one of the diagnoses may be sequenced first.

Consider a patient who is admitted for acute respiratory failure due to exacerbation of congestive heart failure (CHF).

Either condition could be the principal diagnosis, says Cheryl Ericson, MS, RN, CCDS, CDIP, CDI education director for HCPro, a division of BLR in Danvers, Massachusetts. When a patient is admitted with acute respiratory failure and another condition, coders and CDI specialists don’t always agree on the principal diagnosis.

Many coders view these diagnoses as equal and apply the coding guideline regarding two diagnoses that equally meet the definition of the principal diagnosis. The CDI specialist may consider acute respiratory failure as the principal diagnosis, leading to one MS-DRG, while the coder uses congestive heart failure as the principal diagnosis, resulting in a different MS-DRG assignment.

Who wins? Which diagnosis ends up listed as principal? More importantly, do both conditions actually meet the definition of a principal diagnosis? The ICD-9-CM guideline I.B.8.3 for sequencing acute respiratory failure specifically instruct coders:

If the documentation is not clear as to whether acute respiratory failure and another condition are equally responsible for occasioning the admission, query the provider for clarification.

"My goal is to clarify the documentation so that it reflects the provider's intent and accurately paints the clinical picture of which condition occasioned the admission," Ericson says.

In this case, both conditions may not meet the definition of principal diagnosis. Patients with CHF usually are not admitted to the hospital unless they are in acute respiratory distress. Otherwise they won't meet inpatient criteria, Ericson says.

No established diagnosis
Several guidelines identify the appropriate reporting when the physician has not established a definitive diagnosis. If the physician's diagnostic statement identifies a symptom followed by contrasting/comparative diagnoses, the ICD-9-CM Official Guidelines for Coding and Reporting instruct coders to sequence the symptom first (principal diagnosis) and report the contrasting/comparative diagnoses as additional diagnoses.

For example, if the physician's diagnostic statement said chest pain, coronary artery disease (CAD) vs. pneumonia, then chest pain would be the principal diagnosis based on the coding guideline, Avery says.

However, if the physician simply lists two or more contrasting/comparative diagnoses then either can be sequenced first. So if the physician simply wrote CAD vs. pneumonia, then either could be sequenced as principal diagnosis, Avery says. The coder should use the circumstances of the admission, therapy provided, etc., to make the determination if one outweighs the other.

Editor's Note: This article originally published on www.JustCoding.com.