Reference

Clinical Research Glossary

Thirty plain-language definitions to help patients, partners, and the curious read clinical trial materials with confidence.

A

ABI: Ankle-Brachial Index - the ratio of ankle to arm systolic blood pressure, used to screen for and grade peripheral artery disease.
Active Comparator: A trial design in which the investigational therapy is compared against an established active treatment rather than a placebo.
Adverse Event: Any untoward medical occurrence in a clinical trial participant, regardless of whether it is considered related to the investigational therapy.
Ambulatory Surgery Center: A licensed outpatient facility where same-day procedures are performed under sterile conditions, often as an alternative to the hospital setting.
Arrhythmia: An abnormal heart rhythm — too fast, too slow, or irregular. Examples include atrial fibrillation and ventricular tachycardia.
Atherectomy: A catheter-based procedure that removes or modifies plaque from inside an artery, often used in calcified peripheral artery disease.

B

BLA: Biologics License Application - the FDA submission used to approve biologic products such as vaccines, monoclonal antibodies, and gene therapies.

C

CABG: Coronary Artery Bypass Graft - open-heart surgery that uses a vein or artery graft to route blood around blocked coronary arteries.
CDA: Confidential Disclosure Agreement - a contract that protects proprietary information exchanged between a sponsor and a site during feasibility and contracting discussions.
Chronic Venous Insufficiency: A condition in which the leg veins do not return blood to the heart efficiently, causing swelling, skin changes, and venous ulcers.
ClinicalTrials.gov: A U.S. government registry and results database of publicly and privately supported clinical studies conducted around the world.
Composite Endpoint: A single outcome measure built from two or more individual events (for example death, MI, or stroke), used to increase statistical efficiency.
Coronary Artery Disease: Atherosclerotic narrowing of the arteries that supply the heart muscle, which can cause angina, myocardial infarction, or heart failure.
CRA: Clinical Research Associate - the sponsor or CRO representative who monitors a study site to verify data accuracy, regulatory compliance, and participant safety.
CRC: Clinical Research Coordinator - the on-site staff member who manages day-to-day trial operations, including visits, source documentation, and participant communication.
CRF: Case Report Form - the structured document (paper or electronic) used to record protocol-required data for each participant in a clinical trial.
CRO: Contract Research Organization — a company that supports sponsors with trial monitoring, data management, regulatory submissions, and other operational tasks.

D

Data Safety Monitoring Board: DSMB - an independent group of experts that periodically reviews accumulating safety and efficacy data during a trial and can recommend modification or early stopping.
Double-Blind: A trial design in which neither participants nor the treating team know which treatment a participant is receiving, to reduce bias.

E

EDC: Electronic Data Capture - a validated software system used to collect, store, and manage clinical trial data in place of paper case report forms.
Endpoint: A pre-specified outcome measured during a trial to evaluate the safety or efficacy of an intervention.
Exclusion Criteria: Conditions or situations that make a person ineligible for a specific clinical trial, typically for safety or scientific reasons.

F

First Patient In: FPI - the date the first participant in a clinical trial signs informed consent or undergoes the first protocol-defined procedure.
First-in-Human Study: The first time an investigational drug, biologic, or device is administered to human participants, after extensive preclinical testing and regulatory review.

G

GCP: Good Clinical Practice — an international ethical and scientific quality standard for designing, conducting, and reporting clinical trials in human participants.

H

HFmrEF: Heart Failure with mildly reduced Ejection Fraction - heart failure with an LVEF between 41 and 49 percent.
HFpEF: Heart Failure with preserved Ejection Fraction - heart failure with an LVEF of 50 percent or greater, often driven by diastolic dysfunction.
HFrEF: Heart Failure with reduced Ejection Fraction - heart failure with an LVEF of 40 percent or less.

I

ICH-GCP: The International Council for Harmonisation Good Clinical Practice guidelines (currently E6 R3), the global standard for clinical trial conduct and quality.
Inclusion Criteria: The clinical and demographic characteristics a person must have to be eligible for a specific clinical trial.
IND: Investigational New Drug - the FDA application a sponsor submits to legally ship and study an unapproved drug in U.S. clinical trials.
Informed Consent: A written and verbal process in which a participant learns the purpose, procedures, risks, benefits, and alternatives of a study before deciding whether to take part.
Intent-to-Treat: An analysis approach that includes all randomized participants in the groups to which they were originally assigned, preserving the benefits of randomization.
IRB: Institutional Review Board — an independent ethics committee that reviews and approves clinical research protocols and consent documents to protect human participants.

L

Last Patient Visit: LPV - the date the last enrolled participant completes their final protocol-required study visit.
LVEF: Left Ventricular Ejection Fraction - the percentage of blood pumped out of the left ventricle with each beat, used to classify heart failure and guide therapy.

M

MACE: Major Adverse Cardiovascular Events - a composite endpoint commonly defined as cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke.

N

NCT Number: A unique 8-digit identifier (e.g., NCT01234567) assigned to a study registered on ClinicalTrials.gov.
NDA: New Drug Application - the formal request submitted to the FDA to approve a new pharmaceutical for sale and marketing in the United States.
NSTEMI: Non-ST-Elevation Myocardial Infarction - a heart attack with elevated cardiac biomarkers but without ST-segment elevation on ECG, typically managed with urgent but not emergent revascularization.
NT-proBNP: N-terminal pro B-type natriuretic peptide - a blood biomarker released by stretched cardiac muscle, used to diagnose and monitor heart failure.
NYHA Class: New York Heart Association functional class - a four-level scale (I-IV) describing how heart failure symptoms limit a patient's daily physical activity.

P

PCI: Percutaneous Coronary Intervention - a catheter-based procedure that opens narrowed coronary arteries, usually with balloon angioplasty and stent placement.
Per-Protocol Analysis: An analysis that includes only participants who completed the trial as specified in the protocol, complementing the intent-to-treat analysis.
Peripheral Artery Disease: Atherosclerotic narrowing of arteries outside the heart, most often in the legs, that can cause claudication, non-healing wounds, or critical limb ischemia.
Placebo: An inactive comparator used in some trials. Placebo arms are used only when ethically appropriate and typically combined with background standard of care.
Primary Endpoint: The principal outcome a trial is designed to measure, used to determine whether the therapy meets its main objective.
Principal Investigator: The physician-scientist responsible for the conduct of a clinical trial at a given site, including participant safety and protocol compliance.
Protocol Amendment: A formal, IRB-approved written change to an active trial protocol, used to update procedures, eligibility, endpoints, or safety language.
Protocol Deviation: Any departure from the approved trial protocol, ranging from minor visit-window misses to major safety or eligibility violations that must be reported.

R

Randomized Controlled Trial: A study in which participants are assigned by chance to one or more treatment groups, considered the gold standard for evaluating clinical interventions.
Run-In Period: A pre-randomization phase used to standardize background therapy, confirm adherence, or screen out participants unlikely to complete the trial.
Rutherford Class: A 0-to-6 clinical scale describing the severity of peripheral artery disease, from asymptomatic to major tissue loss.

S

SAE: Serious Adverse Event — an adverse event that is fatal, life-threatening, requires or prolongs hospitalization, causes lasting disability, or is otherwise medically important.
Sample Size: The number of participants planned for a clinical trial, calculated to give the study enough statistical power to detect a clinically meaningful effect.
Secondary Endpoint: Additional outcomes measured to provide supportive information beyond the primary endpoint.
Sham Control: A control group that undergoes a procedure mimicking an investigational intervention without the active component, used to isolate the true effect of the therapy.
Site Initiation Visit: SIV - the formal training visit that activates a site for enrollment after contracts, IRB approval, and regulatory documents are in place.
Site Qualification Visit: SQV - a sponsor or CRO visit to evaluate a prospective site's facilities, staff, equipment, and patient population before selecting it for a trial.
Sponsor: The organization (often a pharmaceutical or device company, or an academic group) that initiates, manages, and funds a clinical trial.
Statistical Power: The probability that a trial will detect a true treatment effect of a specified size, conventionally set at 80 to 90 percent.
STEMI: ST-Elevation Myocardial Infarction - a heart attack caused by complete coronary artery occlusion, identified by ST-segment elevation on ECG and requiring emergent reperfusion.
Stratified Randomization: A randomization technique that balances treatment assignment within subgroups (such as age, sex, or disease severity) to ensure comparable arms.
Structural Heart Disease: Disease of the heart's valves, walls, or chambers, often treated with transcatheter or surgical procedures such as TAVR, mitral repair, or septal closure.
Sub-Investigator: A qualified physician or clinician who performs trial-related procedures under the supervision of the principal investigator at a study site.

T

TAVR: Transcatheter aortic valve replacement — a minimally invasive procedure that replaces a diseased aortic valve through a catheter, most often via the femoral artery.

W

Washout: A drug-free interval before or between treatment phases, used to clear prior medications and avoid carryover effects on study outcomes.