Principles of Inpatient Coding: Principal Diagnosis (PDX) And Other Diagnoses (ODX)

Coding skills are divided into basic and advanced. Basic skills are learned in a didactic milieu, and advanced skills are acquired through experience. Basic skills involve knowing what, where, how, and when to code. Advanced coding skills are developed by experience, i.e., the countless hours spent perusing medical records, and understanding all the nuances and myriad of clinical scenarios - in effect, understanding the underpinnings of the official coding guidelines.

In addition to all of the above skills, clear and concise medical record documentation is crucial to arrive at the correct ICD-9-CM code. Good documentation reduces gray areas in coding. It pre-empts misinterpretation and creative (a.k.a. assumptive) coding.

Medical record documentation encompasses notations from physicians, nurses, and other health care practitioners, as well as results of ancillary diagnostic and therapeutic procedures. ICD-9-CM codes are only applied to diagnoses that are shown to have clinical significance as documented by the physician. It is imperative that physician documentation in the progress notes address laboratory data and other diagnostic tests.

Diagnosis coding is a more difficult area than procedure coding because of the complexity of arriving at precise diagnoses and the sequencing of diagnoses and this article will focus on these areas.

The principles governing the correct code assignment and sequencing are based on the American Hospital Association's (AHA) Coding Clinic guidelines, developed by the Cooperating Parties for ICD-9-CM. The National Center for Health Statistics (NCHS) and the Centers for Medicare and Medicaid Services (CMS), formerly HCFA, receive assistance from AHIMA and the American Hospital Association (AHA) in determining official advice for interpretation of the basic principles intended by the classification systems. An Editorial Advisory Board develops official advice, with approval from the Cooperating Parties, for dissemination in "Coding Clinic for ICD-9-CM," a quarterly publication available through the Central Office on ICD-9-CM of the American Hospital Association 1.

Diagnosis Documentation Specificity

The documented diagnosis has to be specific. Case in point - pneumonia caused by specific bacteria should be documented as to the specific organism (e.g., pneumonia due to Klebsiella pneumoniae). If the physician documents only "Pneumonia," even with positive sputum culture(s) for Klebsiella pneumoniae and orders therapy with antibiotics to which the organism is sensitive, this will be coded to 486 - Pneumonia, organism unspecified, rather than 482.0 - Pneumonia due to Klebsiella pneumoniae.

It is important to note that coders cannot assume a diagnosis from clinical information in the medical record 2. "Clinical information" refers to laboratory, pathology and other ancillary results. The physician is required to clearly document the diagnosis in the medical record before the coder can assign the appropriate ICD-9-CM code. There are many factors and nuances that go into diagnosing patients that physicians have been educated and trained to recognize. Coders are not trained as physicians to distinguish false positive or true negative results, e.g., pathology reports, cultures, and chest x-rays.

Pathology reports come back with pathological diagnoses that may or may not be clinically significant. A breast specimen from a radical mastectomy may be negative for carcinoma after an initial local excision biopsy captures all the cancer tissue, but it does not mean that the patient does not have a diagnosis of breast CA. Blood and sputum cultures can be negative because of factors such as: fastidious organisms, prior antibiotic therapy, growth inhibitory factors, and human or mechanical errors.

Chest x-rays may be negative in some patients with pneumonia because of low white blood cell count (WBC) or diminished fluid volume. Pneumonic infiltrates result from the body's defense mechanisms against foreign invaders. Killer white blood cells and other immune system elements in the plasma extravasate into the lung's alveoli to fight the offending bacteria, forming alveolar or interstitial infiltrates seen on chest x-ray. Patients who either have low WBC or decreased fluid volume will not be able to mount a counter-attack in the form of infiltrates. Hence, a false negative chest x-ray. It would be inappropriate to expect coders to pick up these subtle distinctions and assume that a diagnosis is present or not.

Another example of the importance of precise documentation is in the diagnosis of "Anemia." Unless the physician documents that the anemia is due to acute blood loss or is posthemorrhagic (or words to that effect), this will be coded to 285.9 - Anemia, unspecified. It does not matter if there is a documented source of bleeding (e.g., GI bleeding), low hemoglobin/hematocrit, or even that the patient was transfused. Coders cannot assume diagnoses. Acute drops in hemoglobin/hematocrit can also be due to dilutional anemia, wherein the patient's hemoglobin/hematocrit falls because of an artificially expanded fluid volume caused by a medically indicated aggressive intravenous hydration therapy. The use of blood transfusions is not limited to blood loss.

It is only the physician attending to the patient who will be able to recognize the intricacies that each individual case brings. He or she bears the responsibility to document these fine points in the patient's medical record - not just for purposes of coding, but also for continuity of patient care. Physician documentation should provide an accurate depiction of the patient encounter because it inherently affects the quality of patient care. It has been said before - the medical record should be able to stand alone and provide a clear picture of the patient encounter. Contrary to the old adage, "the less said - the better," insufficient documentation only brings more inquiries and potential liability.

Principal Diagnosis (PDX)

This refers to the condition established after study to be chiefly responsible for occasioning the patient's admission to the hospital for care3. The selection of principal diagnosis is determined by the circumstances of admission, diagnostic workup and/or therapy provided4. The condition that best satisfies the three criteria is the principal diagnosis. The documented circumstances of admission, diagnostic workup, and treatment should support and reflect the principal diagnosis. Among the three criteria, the circumstances of inpatient admission always govern the selection of the principal diagnosis. Circumstances of admission refer to the chief complaint, as well as signs and symptoms of the patient on admission. The reason for the patient's admission has to be clearly identified. The principal diagnosis is the definitive diagnosis that was established and should relate to the chief complaint on admission. If it is unclear, the physician should be queried and the outcome should be corroborated with supporting documentation in the medical record.

When two or more diagnoses equally meet the criteria for principal diagnosis as determined by the circumstances of admission, diagnostic work-up, and/or therapy provided (and the Alphabetic Index, Tabular List, or another coding guideline does not provide sequencing direction), any one of the diagnoses may be sequenced first 5. For example, a patient presents with multiple problems: shortness of breath, fever, and chest pain. Chest x-ray demonstrates an exacerbated CHF, examination reveals acute bronchitis, and prior history and current EKG findings are consistent with unstable angina. The three conditions were treated with medications. All three diagnoses equally meet the criteria for the definition of principal diagnosis and the hospital can sequence any one as the principal diagnosis. But let's say this patient undergoes coronary arteriography revealing coronary artery disease (CAD) with 85-90% blockage of two prominent branches and has a percutaneous transluminal coronary angioplasty (PTCA). In this scenario, the workup and therapy criteria clearly distinguish CAD, identified as the etiology of the patient's unstable angina, to be the principal diagnosis.

Other Diagnoses (ODX)

Also known as "secondary diagnoses," or "additional diagnoses," these are conditions that either coexist at the time of admission or develop subsequently and affect patient care for the current hospital episode. "Affecting patient care" signifies conditions requiring any of the following: clinical evaluation, therapeutic treatment, diagnostic procedures, extended the length of hospital stay, or increased nursing care and/or monitoring 6. Thus, a diagnosed condition causing consumption of significant additional hospital resources is considered a valid secondary diagnosis.

Compliance

Compliance mandates that all codes and supporting documentation should be in the medical record prior to billing. Hospital processes should be in place to ensure it. Appropriate use of the physician query process facilitates clarification of gray areas and ensures that supporting documentation is in place. Physician champions, concurrent coders/documentation specialists, and case managers' involvement in concurrent documentation review aids in the timely resolution of emerging problems.

The OIG Compliance Guidance 7 states,

"With respect to reimbursement claims, a hospital's written policies and procedures should reflect and reinforce current federal and state statutes and regulations regarding the submission of claims and Medicare cost reports. The policies must create a mechanism for the billing or reimbursement staff to communicate effectively with the clinical staff. Policies and procedures should:

The Quality Improvement Organization8 (QIO) medical record review process is intended to validate that the medical record information substantiates the diagnosis and procedure codes that the hospital submitted on its claim for Medicare payment. Medical records requested for retrospective QIO review are selected from Medicare's paid claims file - therefore, all of the coding and documentation should already be in place.

This material was prepared by IPRO under a contract with the Centers for Medicare & Medicaid Services (CMS). The contents presented do not necessarily reflect CMS policy.
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