Biological Tests: A Comprehensive Guide PDF

# INSFPM Annexe CHU Mustapha Module Explorations Biologiques Mme O.Benhabiles ## Les Examens Biologiques * Biological tests conducted in a laboratory to analyze biological fluids such as: blood, pleural fluid, urine, cerebrospinal fluid, synovial fluid, ascites, stool, throat swabs, genital swabs,...

# INSFPM Annexe CHU Mustapha Module Explorations Biologiques Mme O.Benhabiles ## Les Examens Biologiques * Biological tests conducted in a laboratory to analyze biological fluids such as: blood, pleural fluid, urine, cerebrospinal fluid, synovial fluid, ascites, stool, throat swabs, genital swabs, etc. * Used to detect abnormalities or confirm normal levels, based on age and sex-specific standards. * Crucial for confirming or disproving diagnoses, monitoring disease progression, and tailoring treatment to the patient's condition. ## Categories of Biological Tests * **Biochemical Tests** * **Glycemia** * **Definition:** Blood glucose level. * **Source:** Derived from food and is the main energy source for cells. Excess glucose is stored as glycogen for later use. * **Regulation:** Blood glucose levels are controlled by pancreatic hormones: insulin and glucagon. * **Indications:** Requested due to symptoms suggesting hyperglycemia or hypoglycemia. * **Diagnostic:** Diabetes is indicated by: * Polydipsia * Polyuria * Glycosuria * Presence of diabetes risk factors, including: * Hypertension * History of gestational diabetes * Obesity * Diabetes monitoring * **Sample:** Venous blood collected after a 8-12 hour fast (preferred) or 2 hours after a meal (postprandial) * **Common Values:** 0.70 to 1.10 g/L (plasma) or 3.9 to 6.1 mmol/L (plasma) * **Urea & Creatinine** * **Definition:** Urea is a small, freely diffusible molecule with identical concentrations in plasma and blood cells. It is a waste product of protein metabolism, produced in the liver, and primarily excreted in the urine. Creatinine is a waste product of muscle metabolism, produced and excreted in the urine. * **Indications:** Used jointly to evaluate kidney function. * **Sample:** Venous blood, preferably fasting. * **Common Values:** * Urea: 0.15 to 0.50 g/L (plasma) or 2.5 to 10 mmol/L (plasma) * Creatinine: * Males: 9 to 13 mg/L (60 to 105 mmol/L) * Females: 7 to 10 mg/L (45 to 80 mmol/L) * Children < 5 years: 15 to 40 mmol/L * **Notes:** Increased levels in both urea and creatinine indicate kidney failure. Decreased levels suggest liver insufficiency. * **Creatinine Clearance** * **Definition:** A measure of glomerular filtration rate, a key indicator of kidney function. * **Calculation:** Calculated from creatinine levels in both urine and blood. * **Indications:** Evaluates kidney function, monitors chronic kidney disease, and helps adjust medication dosages. * **Sample:** 24-hour urine collection and a blood sample at the end of the urine collection. * **Common Values:** 75 to 125 mL/minute. * **Ionogram** * **Definition:** Measurement of electrolytes in blood: sodium (Na+), potassium , calcium (Ca2+), magnesium (Mg2+), chloride (Cl-), and bicarbonate (HCO3-). * **Importance:** Detects electrolyte imbalances that can disrupt metabolism, and monitors intravenous fluid replacement. * **Sample:** Venous blood (5 mL) collected ideally without a tourniquet. * **Common Values:** * Sodium: 135 to 145 mmol/L * Potassium: 3.5 to 4.5 mmol/L * Magnesium : 1.8 to 2.2 mg/L (0.75 to 0.9mmol/L) * Chloride : 95 to 115mmol/L * Bicarbonate : 22 to 26mmol/L * **Lipid Profile** * **Definition:** Measures: * **Total Cholesterol (TC):** Essential component of cell membranes, produced by the liver and obtained from food. * **High-Density Lipoprotein Cholesterol (HDL-C):** "Good Cholesterol" * **Low-Density Lipoprotein Cholesterol (LDL-C):** "Bad Cholesterol" * **Triglycerides (TG):** Fats stored for energy and obtained from diet and liver synthesis. * **Indications:** Assess cardiovascular risk and help detect liver issues. * **Sample:** Venous blood, ideally fasting. * **Common Values:** * TC: 4.1 to 6.2 mmol/L (1.6 to 2.4 g/L). * HDL-C: * Males: 0.4 to 0.5 g/L (1 to 1.3 mmol/L). * Females: 0.5 to 0.6 g/L (1.3 to 1.6 mmol/L). * TG: * Males: 0.45 to 1.75 g/L (0.5 to 2 mmol/L) * Females: 0.35 to 1.40 g/L (0.40 to 1.60 mmol/L) * **Hematological Tests** * **Complete Blood Count (CBC)** * **Definition:** Comprehensive blood test that analyzes: * White blood cells (WBCs) * Red blood cells (RBCs) * Platelets. * **Purpose:** Diagnose and monitor a wide range of conditions, including: * Anemia * Infection * Blood clotting issues * Leukemia * Cancer * **Sample:** Venous blood, ideally collected with minimal delay. * **Common Values:** * RBCs: 4,200,000 - 5,200,000/mm3 (females) or 4,500,000 - 5,500,000/mm3 (males). * Hemoglobin: 12-16 g/100 mL (females), 13 to 17 g/100 mL (males). * Hematocrit: 38 to 48% (females), 42 to 52% (males). * Platelets: 150,000 to 400,000/mm3. * WBCs: 4,000 to 10,000/mm3. * Neutrophils: 40% to 70%. * Eosinophils: 1% to 4%. * Basophils: less than 1%. * Lymphocytes: 20% to 40%. * Monocytes: 4% to 10%. * **Blood Typing and Rh Factor** * **Definition:** Identifies blood types based on the presence or absence of antigens (A, B, or both) on red blood cells and the Rh factor (D protein). * **Importance:** Critical for safe blood transfusions and preventing Rh incompatibility, which can lead to complications during pregnancy for mothers with Rh-negative blood. * **Sample:** Venous blood. * **Coagulation Tests** * **Definition:** Measures how long it takes for blood to clot, aiding in the diagnosis and management of bleeding disorders and in monitoring the efficacy of medications that influence coagulation. * **Common Tests:** * **Prothrombin Time (PT)** * **International Normalized Ratio (INR):** Standardized measure of PT, important for monitoring warfarin therapy. * **Partial Thromboplastin Time (PTT):** Checks the intrinsic clotting pathway. * **Fibrinogen:** Measures fibrinogen levels, a clotting factor produced in the liver. * **Activated Clotting Time (ACT):** Sensitive test used to monitor heparin therapy. * **Sample:** Venous blood. * **Hepatitis B Serology** * **Definition:** Detects hepatitis B virus (HBV) markers in the blood, to determine the presence of infection, past exposure, or immunity from vaccination. * **Importance:** Helps diagnose and manage all stages of the disease, including acute infection, chronic hepatitis, and HBV carriage. * **Tests:** * **Hepatitis B surface antigen (HBsAg):** Indicates active HBV infection, often present during the acute phase. * **Hepatitis B core antibody (anti- HBc):** Present in all stages of infection. * **Hepatitis B e antigen (HBeAg):** Indicates active replication and high infectivity. * **Anti-HBe antibody:** Present in resolved infection or during recovery. * **Anti-HBs antibody:** Indicates immunity from previous infection or vaccination. * **Sample:** Venous blood. * **HIV Serology** * **Definition:** Detects HIV antibodies or viral RNA. * **Importance:** * Diagnoses HIV infection * Monitors disease progression * Guides treatment decisions. * **Tests:** * **ELISA:** Initial screening test. * **Western blot:** Confirmatory test for positive ELISA results. * **Viral Load:** Measures the amount of HIV RNA in the blood, critical for monitoring treatment response. * **Sample:** Venous blood. * **Other Serological Tests** * Depending on your doctor's evaluation and the suspected or known exposure, your doctor may order serology tests for other conditions, such as rubella, cytomegalovirus (CMV), syphilis, or toxoplasmosis, among other infections. ## General Considerations - **Sample Collection** * **Blood:** Usually drawn from a vein in the arm, sometimes from the fingertip. * **Urine:** May require a 24-hour collection. * **Other Bodily Fluids:** Collected as needed, based on the test. - **Timing:** * Many tests require fasting for a specific period before blood is drawn. * Some tests may need to be done at a particular time of day. - **Medication Effects:** Be sure to inform your doctor about all medications and supplements you are taking, as these can affect test results.