HPI stands for "History of Present Illness" and refers to a set of interview questions that a healthcare provider will ask a patient about their chief complaint in order to assist with diagnosing the patient. The HPI is a chronological description of the development of the patients present illness from the first sign and/or symptom or from the previous encounter to the present. It includes elements such as location, quality, severity, duration, timing, context, modifying factors, and associated signs and symptoms. The medical record should describe at least four elements of the present illness (HPI), or the status of at least three chronic or inactive conditions. The HPI is a critical first step in determining the etiology of a patients problem. The combination of the HPI and a physical exam has proven useful in diagnosing the cause of patient complaints. The Centers for Medicare & Medicaid Services (CMS) has defined criteria for a reimbursable HPI, which includes timing, onset, location, duration, quality, severity, content, modifying factors, and associated signs and symptoms.