1 / 40

ITRODUCTION TO

ITRODUCTION TO. Clinical chemistry. Laboratory Technologists and Technicians. Important members of the modern medical team Half of hospital laboratory work involves the clinical chemistry laboratory. Clinical Chemistry.

jerrik
Télécharger la présentation

ITRODUCTION TO

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ITRODUCTIONTO Clinical chemistry Dr. Adnan S. Jaran

  2. Laboratory Technologists and Technicians • Important members of the modern medical team • Half of hospital laboratory work involves the clinical chemistry laboratory Dr. Adnan S. Jaran

  3. Clinical Chemistry • Fundamental science when it seeks to understand the physiologic and biochemical processes in normal and abnormal states. • Applied science when analyses are performed on body fluids or tissue specimens to provide important information for diagnosis or treatment of disease. • The dual nature of clinical chemistry requires that its practitioners be skilled in both phases. • They should have an understanding of the physiologic and biochemical processes occurring in the body as well as technical skills to perform the various tests. Dr. Adnan S. Jaran

  4. The Cell • The basic unit of the body is the Cell • The place where most of the body’s chemical reactions occur. • The cell is an integrated structure with many component parts. • The cell has an outer membrane that separates it from other cells and from the interstitial fluids that bathe them. Dr. Adnan S. Jaran

  5. The Cell • Mammalian cells have a nucleus that contains the genetic material (DNA), and many organized structures or compartments (organelles) in the cytoplasm. • Most of the cellular reactions take place in the organelles. • Organelles are specialized to perform different functions. • The nucleus stores the genetic information Dr. Adnan S. Jaran

  6. The cell • Oxidative reactions for energy production occur in mitochondria. • Protein synthesis takes place on ribosomes. • Cytoplasmic enzymatic reactions occur on cytoplasmic reticulum. • Secretory granules store material for later release. • The cell membrane controls the passage of substances into or out of the cell. • Each organelle perform its function by a series of linked, enzymatic reaction. Dr. Adnan S. Jaran

  7. The cell • Malfunction of a cell may be caused by a variety of factors, such as • Destruction by trauma or invasive agents, including pathogenic microorganisms, viruses and toxins • Genetic deficiency of vital enzyme • Insufficient supply of one or more essential nutrients (amino acids, vitamins, or minerals). Dr. Adnan S. Jaran

  8. The cell 4. Insufficient blood supply 5. Insufficient oxygen supply 6. Malignancy 7. Accumulation of waste products 8. Failure of a control system 9. A defect in the cellular recognition of certain signals Dr. Adnan S. Jaran

  9. ROLE OF THE CLINICAL CHEMISTRY LABORATORY • Most clinical chemistry tests entail measuring the concentration of a particular constituent (Analyte) in body fluids, primarily Blood Plasma or Serum. • Not easy to interpret what is happening at the cellular level when the concentration of an analyte is abnormally high or low; Additional information is needed. Dr. Adnan S. Jaran

  10. Role of the clinical chemistry laboratory • An elevated concentration could be caused by: • Excessive intake • Excessive body synthesis • Deficient utilization • Deficient excretion • Sever dehydration • The reverse is true for a low concentration • Information derived from physical examination and patient's history helps to elucidate the problem • Additional selected tests may be necessary. • Gross abnormalities always indicate thatsomething is wrong! Dr. Adnan S. Jaran

  11. Role of the clinical chemistry laboratory • Diagnosis is difficult to make early in a disease, when symptoms are obscure or absent and changes in concentrations are minimal. • When concentration changes are small, the validity of the test result may be questioned • Precision and Quality control (QC) are necessary and your contributions are essential for good patient care. Dr. Adnan S. Jaran

  12. BASIC PRICIPLES • The clinical chemistry lab. measures chemical changes in the body for diagnosis, therapy, and prognosis of disease. • Primary work of Technologists is the assay of various chemical constituents in blood, urine, and other fluids and tissues. • Normally, the concentrations of constituents are relatively constant. • But, in disease states levels of constituents become altered, the magnitude of change usually paralleling the degree of disease. • In advanced disease, the abnormalities are large and easily detected and present no challenge to the Lab. Dr. Adnan S. Jaran

  13. BASIC PRICIPLES • Early detection of organ dysfunction is much more difficult. • Chemical changes are usually slight and have to be distinguished from possible errors in the performance of the test. • Test accuracy is a prerequisite for proper interpretation of Lab. Test. • Technologist must always keep in mind that each specimen is taken from a person with a real or potential health problem. • Technologist is an essential part of highly skilled team. Dr. Adnan S. Jaran

  14. General Laboratory Information • Most test procedures are quantitative and require careful, precise measurements. • Understanding of the principles of the testing method and some knowledge of the medical uses of the determinations provide the necessary background knowledge for performing the test and understanding their rationale. • Technologists must understand The tools of the trade: equipment, reagents, and the principle and calculations involved in the assay. Dr. Adnan S. Jaran

  15. General Laboratory InformationUnits of Measure • All quantitative measurements must be expressed in clearly defined units that are accepted and understood by all scientists. • The metric system is used in scientific measurements; gram, meter, liter, and seconds are employed as the basic units for expression of Weight, Length, Volume, and Time, respectively. Dr. Adnan S. Jaran

  16. Units of Measure • The recommended units and mode of expression are known as The Systéme Internationale or the SI units. • Table 1. Dr. Adnan S. Jaran

  17. Units of Measure • Units of Length, Weight, and Volume in the metric system were designed to be interrelated with each other. • The liter was originally defined as the volume occupied by one kilogram of water at the temperature of its greatest density (4o C), but in 1964 the definition was changed by international agreement so that the liter is now defined as exactly equal to a cubic decimeter. • The old liter was 1.000028 times as large as the new one. • The cubic centimeter (CC) and milliliter (mL) are synonymous , only mL is accepted in SI. Dr. Adnan S. Jaran

  18. Units of Measure • Measurement of Weight: Balances are used, Analytical balance, single-pan and Top loading, Electronic balance. • Measurement of Length: The meter is used. • Measurement of Volume: Volumetric Equipment are used, Pipets, Volumetric flasks, and Burets, • Measurement of Temperature: The centigrade scale (Celsius or o C), places freezing point of water at 0oC, and boiling point at 100oC. For calculations involving temperature, a scale based on absolute zero is needed. The Kelven scale (o K) employs units identical to those in Celsius system, but its zero point corresponds to absolute zero (0o K) = - 273.15o C. o K = o C + 273. SI, Temp. are expressed as o K, but clinical Labs. Use o C. Dr. Adnan S. Jaran

  19. Units of Measure • Reagent Water: Water is the most commonly used solvent in the clinical Lab. The quality of lab. reagents, and consequently the quality of the laboratory testing, depends on the type of water used. • Laboratory Chemicals: Reagents used for clinical chemistry assays must be made from highly purified chemicals. Analytical grade, HPLC grade. • Primary Standards: a substance that can be accurately weighed or measured to produce a solution of an exactly known concentration and free of impurities. • Laboratory calculations: % solution, weight/volume, vol/vol, weight/weight. SI recognize moles per liter (Mol/L) as mass per volume. Dr. Adnan S. Jaran

  20. Moles, Molarity: molecular weight of a compound expressed in grams. One-molar (1M) solution containing one mole of solute per liter of solution • Gram Equivalent weight: weight of a substance that can combine with or displace, 1.008 g of Hydrogen. • Example: Gram Equivalent weight of Calcium (atomic weight 40.08) • CaCO3 and H2CO3, shows that 40.08 g Calcium (1 mole) displaces 2.016g Hydrogen. Setting up the ratio gives: • 40.08 2.016 2 • ------------ = -------- = --- • Eq wt Ca 1.008 1 • 40.08 • Eq wt Ca = --------- = 20.04 • 2 • This means that the equivalent weight of an element is equal to the atomic weight divided by the number of atoms of Hydrogen with which one atom of that element can combine or that it can replace. Dr. Adnan S. Jaran

  21. Normality : The number of equivalents of solutes present per liter of solution • Hydrated salts : Anhydrous (Na2SO4); Mwt. 142. Heptahydrate (Na2SO4.7H2O) Mwt 268 • Dilutions: Expressed as a ratio of the original volume to the total final volume V1C1 = V2C2 • Conversion of units • Hydrogen ion concentration: pH = - log [H+] • Buffer solutions : A mixture of weak acid and its salt of strong base. Dr. Adnan S. Jaran

  22. QUALITY CONTROL • Every analysis in the lab. generates a result • The validity of that result cannot be taken for granted, however, without some body of supporting evidence. • The most convincing evidence is the establishment of a rigorous comprehensive Quality control program that is faithfully followed • This the only way to guard against the possible deterioration of an analytic system, to become altered to imprecision of results when they occur, and have confidence in test result when everything is in control Dr. Adnan S. Jaran

  23. QUALITY CONTROL • A comprehensive quality control (QC) program consist of all the means used by a laboratory to ensure the reliability of every assay performed on specimens arriving in the lab. • The program includes much more than the analysis of a control serum with every run, and it involves: (1) lab. Director, (2) Technologists, (3) all other personnel who are an integral part of the specimen collecting, and (4) The analytical system. Dr. Adnan S. Jaran

  24. QUALITY CONTROL • Responsibility of the director or supervisor • Select the most accurate and precise analytical method • Adequately train and supervise the activities of lab. Staff • Make available printed procedures for each method, with directions, an explanation of the chemical principles, reference values (Normal range). • Select good instruments and institute a regular maintenance • Institute a good quality control program, provide control sera, inspect control charts. • Conduct continuing education sessions with technologists • Document the preceding steps for accrediting group. Dr. Adnan S. Jaran

  25. QUALITY CONTROL • The role of the Technologist • Fellow assay directions explicitly • Use the proper control serum for each run, chart the results, and take appropriate action when the control serum result is beyond the established limts. • Always use sound, analytical techniques • Be conscientious in instrument maitenance • Notify the supervisor immediately when analytical problems develop and when unusual or life-threatening results are obtained on a patient. Dr. Adnan S. Jaran

  26. Precision & Accuracy • The first step in the establishment of a quality control program is to ascertain the limits of uncertainty for each test. • Every measurement, every analysis carries with it a degree of uncertainty, a variability in the answer as the test is performed repeatedly. • It is essential to determine the precision of each test, which reflects the reproducibility of the test. • Precise means "exact, as in performance, execution, or amount. "In physical science it means "repeatable, reliable, getting the same measurement each time." • The less the variation, the grater the precision. Dr. Adnan S. Jaran

  27. Precision & Accuracy • Precision must not be confused with Accuracy. • Accuracy is the deviation from the true results. • Accurate means "capable of providing a correct reading or measurement." In physical science it means 'correct'. A measurement is accurate if it correctly reflects the size of the thing being measured. • An analytical method may be precise but inaccurate because of a bias in the test method, e.g. Folin-Wu glucose method. Dr. Adnan S. Jaran

  28. High accuracy, but low precision Dr. Adnan S. Jaran

  29. High precision, but low accuracy Dr. Adnan S. Jaran

  30. This is a precise pattern, but not accurate. The darts are clustered together but did not hit the intended mark. This is a randomlike pattern, neither precise nor accurate. The darts are not clustered together and are not near the bull's eye. Dr. Adnan S. Jaran

  31. This pattern is both precise and accurate. The darts are tightly clustered and their average position is the center of the bull's eye. This is an accurate pattern, but not precise. The darts are not clustered, but their 'average' position is the center of the bull's eye. Dr. Adnan S. Jaran

  32. Precision & Accuracy • The degree of precision of a measurement is determined from statistical considerations of the distribution of random error; it is best expressed in terms of Standard Deviation • A normal frequency curve (bell-shaped, Gaussian curve) is obtained by plotting the values from multiple analysis of a sample against the frequency of occurrence. Dr. Adnan S. Jaran

  33. Accuracy indicates proximity to the true value, precision to the repeatability or reproducibility of the measurement Dr. Adnan S. Jaran

  34. Precision & Accuracy • Control Specimens: • Every assay performed in the Lab. generates a set of numbers (usually a patient’s test results), requested by the physician. • Even though the procedures and methods used in the tests is known to be satisfactory, there is no guarantee that every thing is working perfectly on any particular day. Dr. Adnan S. Jaran

  35. Precision & Accuracy • The instrument may be out of calibration, Standards or reagents may be deteriorating, The technologist may have made an error. • Therefore, it is necessary to check every assay, every time its done in the Lab. the simplest way is to include a control specimen in the run. • Control specimens may be purchased, or use pooled serum, more than one control specimen is used with each run, High, Low and Normal. Use of blind control and external control. Dr. Adnan S. Jaran

  36. Precision & Accuracy • Evaluation of a new methodology • Every laboratory seeks to improve its methodology as technology advances, new technology are designed, and new assays are introduced. • New method cannot be accepted on faith; it must be rigorously tested and shown to meet the criteria established by the clinical laboratory. Dr. Adnan S. Jaran

  37. Precision & Accuracy • First step in testing the new method is with-run precision (used to test one sample repeatedly) • Second step day-to-day precision at normal and abnormal levels over 20 day period. • The new method is then compared to the current method or a reference method (40 samples split between the methods) and assayed, The a correlation curveis done to compare. Dr. Adnan S. Jaran

  38. Dr. Adnan S. Jaran

  39. Dr. Adnan S. Jaran

  40. Dr. Adnan S. Jaran

More Related