Understanding Clinical Trials: Phases Terms and Lab Results
This page explains Clinical Trial Phases, common Research Terms, and frequently used Blood and Urine Lab Test Codes- all in plain language to help participants better understand what they may see during the study.
Clinical Trial Phases Defined
PHASE 1 - First time in human dosing. Focuses on safety, dose levels, and how the drug moves through the body (PK).
PHASE 2 - Looks at how well the drug works and continues to monitor safety. Uses a larger group and helps to optimize effective dosing.
PHASE 3 - Confirms effectiveness and safety in a much larger populations. Often used for FDA approval decisions.
PHASE 4 - Happens after FDA approval. Monitors long-term safety, side effects, and real world use.
Healthy Volunteer vs Patient Studies
While clinical trials are often described by Phases (Phase 1, Phase 2, Phase 3 etc), the type of participants can differ.
Healthy volunteer studies most commonly occur in Phase 1 and focus on safety, dosing, and how a drug behaves in the body. These studies are often compensated and do not provide any medicinal benefit to the participant .
Patient (disease-specific) studies enroll humans who already have the condition being studied. These are more common in Phase 2 and Phase 3 trials and focus on how well the drug works. Compensation in these studies is usually limited to travel or expense reimbursement rather than study pay compensation.
Common Clinical Trial Terms & Definitions
Adverse Event (AE) – Any unwanted medical issue that happens during a study, whether or not it is caused by the study drug.
Baseline – Measurements taken before the study begins, used for comparison later.
Blinded / Blinding – When participants and/or researchers do not know who is receiving the study drug or placebo.
Cohort – A group of participants in a study who receive the same dose or treatment.
Comparator – A drug or placebo used to compare against the study drug.
Compliance – How closely a participant follows study instructions.
Concomitant Medications – Other medications a participant is taking during the study.
Contract Research Organization (CRO) – A company hired to manage or run clinical trials for sponsors.
Data Safety Monitoring Board (DSMB) – An independent group that reviews safety data during a study.
Dose Escalation – Gradually increasing doses to evaluate safety and tolerability.
Double-Blind – Neither participants nor researchers know who receives the drug or placebo.
Efficacy – How well the study drug works.
Eligibility Criteria – The rules that determine who can or cannot join a study.
Endpoints (Primary / Secondary) – The main outcomes a study is designed to measure.
FDA (Food and Drug Administration) – The U.S. agency that regulates drugs and clinical trials.
First-in-Human (FIH) – The first time a drug is tested in humans, usually in Phase 1.
Half-Life – How long it takes for half of a drug to leave the body.
Healthy Volunteer – A participant without the condition being studied.
Inclusion Criteria – Requirements a participant must meet to join a study.
Informed Consent Form (ICF) – The document that explains the study and participant rights.
Institutional Review Board (IRB) – A committee that reviews studies to protect participantafety and rights.
Investigational Product (IP) – The drug or treatment being studied.
Open-Label – Everyone knows what treatment is being given.
PD (Pharmacodynamics) – How the drug affects the body.
PK (Pharmacokinetics – How the drug moves through the body (absorption, distribution, metabolism, elimination).
Placebo – A substance with no active drug used for comparison.
Placebo-Controlled – A study that compares a drug to a placebo.
PI-(Principal Investigator) -The lead doctor responsible for conducting the study at a research site .
Protocol – The written plan for how a study is conducted.
Sentinel Dosing – Giving the drug to a small number of participants first to check safety.
Serious Adverse Event (SAE) – A severe medical event such as hospitalization or death.
Single-Blind – The participant does not know which treatment they receive, but researchers do.
Sponsor – The company or organization funding the study.
Study Arm – A specific group in a study receiving a certain treatment
Tolerability – How well participants handle the drug’s side effects.
Washout Period – Time allowed for previous drugs to leave the body before a study starts.
Lab Tests: Codes & Definitions
A-G
Blood
Albumin (ALB) - Protein made by the liver; helps keep fluid in the bloodstream and reflects nutrition and liver function.
Alkaline Phosphatase (ALP / ALKP) -Enzyme related to liver and bone health.
Alanine Aminotransferase (ALT / SGPT) -Liver enzyme; elevated levels can indicate liver injury.
Amylase- Enzyme related to pancreas function and digestion.
Aspartate Aminotransferase (AST / SGOT)- Enzyme found in liver and muscles; used with ALT to assess liver health.
Basophils (BAS / BASO) - Type of white blood cell involved in allergic and inflammatory responses.
Bilirubin, Total (TBIL) -Breakdown product of red blood cells; reflects liver function and bile flow.
Blood Urea Nitrogen (BUN)- Waste product filtered by the kidneys; reflects kidney function and hydration.
Calcium (CA) -Mineral important for bones, muscles, nerves, and heart function.
Carbon Dioxide, Total (CO2) - Helps evaluate acid–base balance and lung/kidney function.
Chloride (CL) - Electrolyte that helps maintain fluid balance and acid–base status.
Creatine Kinase (CK)-Enzyme released with muscle injury or strain.
Creatinine (CREA) - Waste product filtered by kidneys; key marker of kidney function.
Cystatin C (CYSTC)- Alternative kidney function marker, sometimes used with eGFR.
D-Dimer - Marker related to blood clot formation and breakdown.
Eosinophils (EOS) - White blood cells involved in allergies, asthma, and parasitic infections.
Estimated Glomerular Filtration Rate (eGFR) - Calculated value showing how well the kidneys are filtering blood.
Fibrinogen (Clauss) - Protein involved in blood clotting.
Glucose (GLU) Blood sugar level; reflects energy metabolism.
Gamma-Glutamyl Transferase (GGT) Liver enzyme often used with other liver tests.
Globulin -Group of blood proteins involved in immune function.
Alcohol, Ethyl (Urine Ethanol)- Screens for recent alcohol use.
Amphetamines _ Drug screen for stimulant substances.
Appearance -Aisual clarity of urine (clear, cloudy, etc.).
Bacteria - Checks for presence of bacteria that may indicate infection.
Barbiturates -Drug screen for sedative medications.
Benzodiazepines -Drug screen for anti-anxiety or sedative medications.
Bilirubin -May indicate liver or bile duct issues if present.
Blood / Occult Blood -Detects blood not visible to the eye.
Cannabinoids (Marijuana Metabolites / THC) -Drug screen for marijuana use.
Chloride (Urine) -Electrolyte balance assessment (less common in screening).
Cocaine Metabolites -Drug screen for cocaine use.
Color -Normal urine color ranges from pale yellow to amber.
Creatinine (Urine) -Used to assess urine concentration and sample validity.
Ethanol, Urine Qualitative -Confirms presence or absence of alcohol.
Glucose - Detects sugar in urine; may indicate diabetes or stress response.
Hemoglobin (HGB)- Protein in red blood cells that carries oxygen.
Hematocrit (HCT) Percentage of blood made up of red blood cells.
Immature Granulocytes (IMG) - Early white blood cells; may increase during infection or inflammation.
Lactate Dehydrogenase (LD / LDH) - Enzyme released with tissue damage.
Lipase - Pancreatic enzyme; elevated levels may indicate pancreatic issues.
Lymphocytes (LYM) - White blood cells important for immune response.
Magnesium (MG) - Mineral important for muscle, nerve, and heart function.
Mean Corpuscular Hemoglobin (MCH) - Average amount of hemoglobin per red blood cell.
Mean Corpuscular Hemoglobin Concentration (MCHC) - Average concentration of hemoglobin in red blood cells.
Mean Corpuscular Volume (MCV) - Average size of red blood cells.
Mean Platelet Volume (MPV) - Average size of platelets.
Monocytes (MONO) - White blood cells involved in immune defense and inflammation.
Neutrophils (NEU) - White blood cells that fight bacterial infections.
Phosphorus / Phosphate - Mineral important for bones, energy, and kidney function.
Platelets (PLT) - Cells involved in blood clotting.
Potassium (K) - Electrolyte critical for heart and muscle function.
Protein, Total (TP) -Total amount of albumin and globulin in blood.
Red Blood Cells (RBC) - Cells that carry oxygen throughout the body.
Red Cell Distribution Width (RDW) - Measure of variation in red blood cell size.
Sodium (NA) - Electrolyte that regulates fluid balance and nerve function.
Uric Acid (URIC) - Waste product; elevated levels can be associated with gout.
White Blood Cells (WBC) - Cells that fight infection and inflammation.
Urine
H-Z
H-Z
hCG (Pregnancy Test) -Detects pregnancy hormone.
Ketones -May indicate fasting, dehydration, or altered metabolism.
Leukocyte Esterase -Marker of white blood cells; may suggest infection.
Marijuana Metabolites (THC) - Drug screen for cannabis use.
Methadone -Drug screen for opioid replacement therapy.
Nitrite -Suggests bacterial infection if positive.
Opiates -Drug screen for opioid substances.
pH =Measures acidity or alkalinity of urine.
Phencyclidine (PCP) -Drug screen for PCP.
Protein -Protein in urine may indicate kidney stress or dehydration.
Red Blood Cells (RBC) -Microscopic blood in urine.
Specific Gravity -Shows how concentrated or diluted urine is.
Squamous Epithelial Cells -Indicates sample quality or contamination.
Urobilinogen -Related to liver function and red blood cell breakdown.
White Blood Cells (WBC) -May indicate infection or inflammation.
Special Note: Not all clinics test for every item listed here.
Required labs vary by study, protocol, and sponsor. This list is intended to provide a comprehensive reference of commonly used blood tests so volunteers can better understand lab results they may encounter during screening or participation
Most clinics will provide screening and laboratory results to participants upon request. Some clinics release results during the study, while others may provide them after study completion, and assigned HIPAA authorization is often required.
Having access to these results can help volunteers feel more informed, prepared, and confident about their health. HVA encourages participants to request and retain copies of their screening and laboratory results, as they can be valuable for tracking health before and after study participation!