Patient classification system that categorizes patients who are medically related with respect to principal diagnosis, presence of a surgical procedure, age, presence or absence of significant complications, treatment, and who are statistically similar in length of hospital stay. Medicare hospital insurance payments are based on fixed dollar amounts for a principal diagnosis as listed in DRGs regardless of the amount of charges accrued. See all patient diagnosis-related group (APDRG or AP-DRG) and inpatient prospective payment system (IPPS) .

Medical service performed such as biopsy, thyroid function test, or radiographic procedure to establish the cause of the patient’s complaints and symptoms.

Registration of a patient either as an inpatient or outpatient primarily for diagnostic purposes in a health care facility.

Book published by the American Psychiatric Association that lists diagnostic criteria and terminology that is widely accepted as the preferred language of mental health clinicians and researchers.

Diagnostic code book used by mental health clinicians as the system for substance abuse and mental health patients.

1. Numerical three-, four-, or five-digit code located in the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code book and assigned to a patient’s medical condition, symptoms, or reason for the encounter as documented in the patient’s medical record. 2. Up to seven-digit code located in the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) . The code is assigned to a patient’s medical condition, symptoms, or reason for the encounter that is documented in the patient’s medical record (see Figure D-1, A ). 3. When the physician’s office or an outpatient hospital is billing, the primary diagnosis code(s) is inserted in Block 21 of the CMS-1500 insurance claim form. For inpatient hospital billing, the principal diagnosis code is inserted in Field 66 and subsequent diagnosis codes in Fields 67 through 75 of the UB-04 insurance claim form. Diagnostic codes.