Clinical Biochemistry Tests PDF

Clinical biochemistry First grade Dr. Sarah I. Abbas  Clinical Biochemistry In this class you will gain the range of tests to help clinicians diagnose, treat, and monitor the recovery of patients. Detecting pathological changes in biological systems requires an under...

Clinical biochemistry First grade Dr. Sarah I. Abbas  Clinical Biochemistry In this class you will gain the range of tests to help clinicians diagnose, treat, and monitor the recovery of patients. Detecting pathological changes in biological systems requires an understanding of the 'biomarker' changes that occur - and the reliability of tests that can detect those changes. Clinical Biochemistry involves the use of biochemical measurements to support the diagnosis, treatment, prevention and monitoring of disease. Whole blood / Plasma / serum Whole blood / Plasma / serum  Clinical Biochemistry The analysis of individual constituents, proteins, enzymes, nutrients, waste products, metabolites, hormones, etc. in blood or body fluids that provides information regarding the function or integrity of a tissue or organ. The clinical chemistry laboratory measures change in biochemical compounds as an indicator of health status or disease processes.  Specimens Collection in Biochemistry Laboratory Phlebotomy Procedure: 1- Wash hands thoroughly before beginning any phlebotomy procedure. Be sure to check the expiration dates on tubes before proceeding. 2- Confirm that the identity of the patient is matching with the requisition form before collecting the specimen. 3- Explain the procedure including small risks of hematoma, slight pain and some light-headedness. 4- On a table desk, assemble all necessary equipment: cotton/gauze, tubes, safety needle, alcohol swab, tourniquet, gloves and band aid.  Specimens Collection in Biochemistry Laboratory 5- Position the patient so that they seated comfortably in a chair with their arm extended on a desk to form a straight line from the shoulder to the wrist. The patient's arm and elbow should be firmly supported and not bent at the elbow. 6- Check both arms to select the larger and fuller veins. Palpate and trace the path of the veins several times with your finger. Tap the vein at the site of the draw with two fingers; this will cause the vein to dilate. The following factors should be considered in site selection: a) Extensive scarring: Healed burns areas or scar tissue should be avoided.  Specimens Collection in Biochemistry Laboratory b) Specimen collected from an area with a hematoma may yield false test results. If another vein site is not available, the specimen should be collected distal to the hematoma. 7- Apply the tourniquet. 8- Ask the patient to open and close his fist so his vein becomes prominent. tough hand pumping is not necessary to activate blood flow and should be avoided. 9- Clean the vein puncture site with the alcohol swab in a circular motion from the center of the area to the outside. Allow the area to air dry to prevent hemolysis and a burning sensation to the patient.  Specimens Collection in Biochemistry Laboratory 10- Insert the needle into the vein with the bevel facing upward and provide stability on the arm, once the blood flow has begun have the patient open his fist. 11- Fill the tube and place a cotton/gauze piece over the site. All used needles must be disposed. Apply pressure to the site for 2-5 minutes. Place a band aid over the puncture site. 12- Again verify that the information on the sample tubes match the requisition form. 13- Remove gloves and dispose of in a properly container. Wash hands thoroughly after phlebotomy  Specimens Collection in Biochemistry Laboratory Additional Vein Puncture Considerations 1- Prevention of Hematoma: a) Puncture only the uppermost wall of the vein. b) Release the tourniquet before removing the needle from the vein. c) Use only major veins (not superficial veins). d) Make sure that the needle fully penetrates the uppermost wall of the vein. Partial penetration may allow blood to leak into the soft tissues surrounding the vein by way of the needle bevel. e) Apply a small amount of pressure to the area with the cotton/gauze pad when bandaging the arm.  Specimens Collection in Biochemistry Laboratory 2- Prevention of Hemolysis: a) Mix anticoagulant specimen thoroughly by inverting each tube gently 8-10 times. Don't shake, tough mixing may cause hemolysis. b) Avoid drawing blood from an area with a hematoma. c) Ascertain that the vein puncture site is dry without touching it. If a blood sample is unobtainable: a) Change the position of the needle. If the needle has penetrated too far into the vein, pull it back slightly. If it has not penetrated far enough, advance it farther into the vein. Rotate the needle a half turn. a) Try another tube, the tube may not have sufficient vacuum.  Specimens Collection in Biochemistry Laboratory c) Loosen the tourniquet. It may be applied too tightly, thereby stopping the blood flow. Reapply the tourniquet loosely. d) Probing for the vein is not recommended as it is painful to the patient. In most cases, another puncture in a site below the first site is advised. e) Never attempt a vein puncture more than twice. Have another person attempt to draw the specimen. Specimen Handling: 1- Gently invert all tubes with anticoagulants 8-10 times.  Specimens Collection in Biochemistry Laboratory 2- Ensure all tubes are labeled with identification number and second identifier (first and last names of patient). 3- Allow at least 10- 20 minutes (no more than 45 minutes) for the blood to clot prior to centrifuging in upright position. Centrifuge the tube for 5- 10 minutes at 2500-3500 RPM and transfer the serum into a properly labeled pour-off tube using a disposable pipette. 4- Some other factors that can affect the sample are: a) Hemolysis: it is the breaking down of red blood cells (RBC) because of:  Specimens Collection in Biochemistry Laboratory i) Time: Holding blood over 2 hours before centrifuging can and usually lead to hemolysis. ii) Temperature: Never store blood in too warm area, hot cars, hot sun, etc. Allowing blood to freeze in cold weather will also produce hemolysis. iii) Trauma: Going through the vein, accessing a collapsed vein or using a small needle can cause hemolysis. Squeezing the finger is the main cause of hemolysis. b) Lipemia: it is an abnormal amount of fat in the blood. This is usually caused by the patient not fasting Hematoma Hemolysis  Collection Tubes : 1- Mottled Red Top: contains clot activator with gel separator in the bottom for collection of serum samples. 2- Red Top: contains no anticoagulants for collection of serum samples. 3- Purple Top: contains EDTA (ethylenediaminetetraacetate) for collection of hematology and hemoglobin analysis samples. 4- Green Top: contains sodium heparin for hematology and chemistry samples. 5- Gray Top: contains sodium fluoride and potassium oxalate which are glycolysis inhibitors. 6- Light Blue Top: contains sodium citrate for coagulation samples. 7- Royal Blue Top: may contain sodium heparin for trace metal studies. Centrifuge  Factors affecting of parameters Age. Gender. Ethnicity. Altitude. Physiological conditions (e.g. at rest, after exercise, standing, lying). Sampling methods (e.g. with or without using tourniquet). Storage and age of sample. Container used, e.g. for blood sample, anticoagulant. Method of analysis  Reliability of diagnosis Evaluation of all of the below increases the reliability of diagnosis: 1. No diagnosis should be made on the basis of a single test result 2. Information from initial patient consultation 3. Physical examination findings 4. Personal and family history 5. Previous test results  Disorders of Carbohydrates metabolism (Diabetes Mellitus) Diabetes Mellitus (WHO): ▪ 1980: 108 million people diagnosed ▪ 2014: 422 million people diagnosed ▪ 2016: 1.6 million deaths (The seventh leading cause of death) Its is a major cause of : 1) Blindness 2) Kidney failure 3)Heart attacks 4)Stroke 5)Lower limb amputation.  Regulation of Carbohydrate Metabolism The liver, pancreas, and other endocrine glands are all involved in controlling the blood glucose concentrations within a narrow range. During a brief fast, glucose is supplied to the blood from the liver through glycogenolysis. When the fasting period is longer than 1 day, glucose is synthesized from other sources through gluconeogenesis.  Control of blood glucose is under two major hormones: insulin and glucagon, both produced by the pancreas. Their actions oppose each other. Other hormones and neuroendocrine substances also exert some control over blood glucose concentrations, permitting the body to respond to increased demands for glucose or to survive prolonged fasts. It also permits the conservation of energy as lipids when excess substrates are ingested. Carbohydrate Digestion Some tissues, such as the brain, red blood cells (RBCs), kidney medulla, lens and cornea of the eye, testes, and exercising muscle, require a continuous supply of glucose as a metabolic fuel. Liver glycogen, an essential postprandial source of glucose, can meet these needs for only 10–18 hours in the absence of dietary intake of carbohydrate. During a prolonged fast, however, hepatic glycogen stores are depleted, and glucose is formed from noncarbohydrate precursors such as lactate, pyruvate, glycerol (derived from the backbone of triacylglycerols and α-keto acids (derived from the catabolism of glucogenic amino acids.  Blood Glucose Abnormalities Dysglycemia: Dysglycemia is a broad term that refers to an abnormality in blood sugar stability. This can include hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar). HYPERGLYCAEMIA AND DIABETES MELLITUS Hyperglycaemia may be due to: intravenous infusion of glucose-containing fluids, severe stress (usually a transient effect) such as trauma, myocardial infarction or cerebrovascular accidents, diabetes mellitus or impaired glucose regulation Diabetes mellitus It has been defined by the World Health Organization (WHO), on the basis of laboratory findings: if the venous plasma glucose concentration is 7.0 mmol/L or more (fasting) and/or 11.1 mmol/L or more 2 h after the oral ingestion of the equivalent of 75 g of anhydrous glucose. Diabetes mellitus can be classified into the following categories: 1) Type 1 diabetes mellitus Previously called insulin-dependent diabetes mellitus, this is the term used to describe the condition in patients for whom insulin therapy is essential because it is caused by an absolute or relative insulin deficiency. It usually presents during childhood or adolescence. Most of these cases are due to immune-mediated processes and may be associated with other autoimmune disorders. 2) Type 2 diabetes mellitus Previously called non-insulin-dependent diabetes mellitus, this is the most common variety worldwide (about 90 per cent of all diabetes mellitus cases). Insulin may sometimes be needed. Onset is most usual during adult life; there is a familial tendency and an association with obesity. 3) Gestational diabetes mellitus In the UK, about 4–5 percent of pregnancies are complicated by gestational diabetes mellitus (GDM). It is associated with increased fetal abnormalities, for example high birth weight, cardiac defects. In addition, birth complications, maternal hypertension and the need for caesarean section may occur. Women at high risk for GDM include those who have had GDM before, have previously given birth to a high-birth weight baby, are obese, have a family history of diabetes mellitus and/or are from high- risk ethnic groups, for example black or South Asian. If fasting venous plasma glucose is 7.0 mmol/L or more and/or the random measurement gives a concentration of 11.1 mmol/L or more (some doctors prefer to use a lower cut-off of about 9.0 mmol/L in pregnancy), the woman has GDM. These women should be screened at the earliest opportunity and, if normal, retested at about 24– 28 weeks, as glucose tolerance progressively deteriorates throughout pregnancy.  Monitoring of diabetes mellitus Glycosuria Glycosuria can be defined as a concentration of urinary glucose detectable using relatively insensitive, but specific, screening tests. These tests often depend on the action of an enzyme, such as glucose oxidase, incorporated into a diagnostic strip. Glycosuria, as defined above, occurs only when the plasma, and therefore glomerular filtrate, concentrations exceed the tubular reabsorptive capacity. This may be because the plasma and glomerular filtrate concentrations are more than about 10 mmol/L. , and therefore the normal tubular reabsorptive capacity is significantly exceeded.  Very rarely, if the glomerular filtration rate is much reduced, there may be no glycosuria despite plasma glucose concentrations more than 10 mmol/L. A diagnosis of diabetes mellitus should never be made on the basis of glycosuria.  Blood glucose Blood glucose concentrations may be measured using glucose testing reagent strips. The colour change of the strip can be assessed visually or by using a portable glucose meter and the reaction often involves an enzyme determination of glucose, for example glucose oxidase. Although the measurement of blood glucose concentrations involves the discomfort of several skin punctures, many motivated patients are able to adjust their insulin dose more accurately based on these results than on those obtained by testing their urine. Glycatedhaemoglobin (HbA1c) is formed by non-enzymatic glycation of haemoglobin and is dependent on: the mean plasma glucose concentrations and on the lifespan of the red cell; falsely low values may be found in patients with haemolytic disease. Measurement of blood HbA1c may not reveal potentially dangerous short-term swings and nor does HbA1c detect hypoglycaemic episodes and thus plasma glucose estimations may also be useful.  This was expressed as a percentage of total blood haemoglobin concentration and gives a retrospective assessment of the mean plasma glucose concentration during the preceding 8-12 weeks. The higher the glycatedhaemoglobin, the poorer the mean diabetic or glycaemic control. (Normal range: 4.6-6.4%). It has been suggested that an HbA1c of greater than 6.5 per cent is diagnostic of diabetes mellitus, but this is not universally agreed as other factors such as haemoglobin variants and abnormal erythrocyte lifespan may affect HbA1c levels.  Procedure of Oral glucose tolerance test (OGTT) Before starting this test, contact your laboratory: local details may vary. The patient should be resting and should not smoke during the test. The patient fasts overnight (for at least 10 h but not more than 16 h). Water, but no other beverage, is allowed. A venous sample is withdrawn for plasma glucose estimation. A solution containing 75 g of anhydrous glucose in 300 mL of water is hyperosmolar, and not only may cause nausea and occasionally vomiting and diarrhoea, but also, because of delayed absorption, may affect the results of the test.  HYPOGLYCAEMIA By definition, hypoglycaemia is present if the plasma glucose concentration is less than 2.5 mmol/L in a specimen collected into a tube containing an inhibitor of glycolysis, for example fluoride oxalate. Blood cells continue to metabolize glucose invitro, and low concentrations found in a specimen collected without such an inhibitor can be dangerously misleading (pseudohypoglycaemia). Symptoms of hypoglycaemia may develop at higher concentrations if there has been a rapid fall from a previously raised value, when adrenaline secretion is stimulated and may cause sweating and tachycardia..  Case: A 26-year-old man was referred to the local diabetes clinic in coma. He had been diagnosed as having type 1 diabetes 3 years previously and his control was poor (HbA1c 9.6%). Several close family members also had diabetes, FBS:2.5 mmol/L. He was injected with glucose saline, FBS: 12 mmol/L. give your explanation.