Clinical laboratory science consists of various specialties such as clinical chemistry, hematology, immunology, microbiology, serology, toxicology and pathologyClinical Chemistry is an exciting field that combines analytics and instrumentation with information technology and management of workflow, staff efficiencies and high volume automation. The field is ever-changing and demands staff have skills in the methodologies and their limitations, technology and troubleshooting equipment, as well as management and ability to adapt operations to evolving clinical needs. At the heart, the laboratory is a service to the physician providing test results that are critical to diagnosing and managing patients. But, the laboratory is also a vital member of the healthcare team and gets involved in utilization, operational efficiencies and improving patient outcomes. course contentsIntroduction to clinical chemistryanalytes that are measured using clinical chemistry testsTypes of biologic specimens that may be used for testing How the results of tests are interpreted Measurement principales optical (photometric) and electrochemical (potentiometric) that are most often used to determine concentrations of analytes in the clinical chemistry laboratory. he difference between an endpoint and a rate reactionthe principle of potentiometric measurementChemical reactions of analytes produce products that can be detected by using optical methods; changes in light absorbed, scattered or emitted by these products are used to determine the concentration of the analyte.2. In potentiometric methods, changes in concentrations of ions are sensed as potential differences between two electrodes. 3. Calibrators, solutions of known concentration, are used to establish the relationship between the magnitude of an optical or electrical signal and the corresponding concentration of analyte. Quantitation of routine chemistry analytes is typically based on one of two measurement principles measurement of light (photometry or spectrophotometry) or measurement of electrochemical potential (potentiometry). There are many variations of photometry and potentiometry, but all have in common that the signal the amount of light or electrical voltage is predictably related to the amount of analyte in solution. Accurate test result is our aimDistinguish between precision and accuracy Describe how calibrator values are assigned Identify the roles of proficiency testing (PT)/external quality assurance (EQA) and quality control testing programs in ensuring accuracy of test results1. Laboratory tests must meet precision and accuracy standards.2. Accuracy, closeness to a true value, depends on a valid calibration process.3. Calibrator value assignment is linked to a certified reference material, a recognized reference method or a consensus process that provides traceability.4. Laboratories use quality control and proficiency testing to monitor the precision and accuracy of test methods. Test for analytes in amixturesMeasurement of one substance when it is part of a complex mixture of substances provides special challenges. A measurement method that works well for determining the amount of an analyte in a relatively pure form may be completely unsatisfactory when the analyte is in a mixture of cells, proteins, lipids, carbohydrates and trace minerals. Methods for the analysis of analytes in complex biologic mixtures require special approaches to minimize or eliminate interference from other substances. Some of the approaches frequently used in clinical chemistry such as blanking, rate methods, pretreatment, reagent specificity and ion-selective electrodes are described in more detail in the following sections. where you can find errors?preanalytical, analytical and postanalytical errors1. Patient preparation and proper collection and handling of specimens are important preanalytical steps to ensure the validity of a test result.2. Hemolysis, icterus and lipemia (HIL) are three of the most common sources of interfering substances found in blood serum and plasma samples. Hemolyisis refers to color of hemoglobin released from destroyed red blood cells Icterus refers to color from bilirubin Lipemia refers to turbidity from high lipid concentrations, usually triglycerides If unrecognized, their presence may cause overestimation or underestimation of the analyte concentration.3. Automated instrumentation includes numerous algorithms to detect potential sources of error and alert the operator. common clinical chemistry tests 1. Clinical chemistry tests measure a wide variety of analytes that reflect many different organ systems and diseases.2. Some test results are specific indicators for a single organ system or disease; others are general indicators of a disease or disorder, but do not pinpoint the specific organ or disease process. 3. Tests are performed for different reasons. Some tests help diagnose a disease, others monitor the course of the disease progression or effectiveness of therapy, and still others are used to screen for risk
