Introduction to clinical chemistry

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

Introduction to clinical chemistry: 

Introduction to clinical chemistry Abdul zinco

Introduction cont.: 

Introduction cont. Definition : Clinical chemistry (also known as clinical biochemistry , chemical pathology , medical biochemistry or pure blood chemistry ) is the area of pathology that is generally concerned with analysis of bodily fluids .

Introduction cont.: 

Introduction cont. The discipline originated in the late 19th century with the use of simple chemical tests for various components of blood and urine. Subsequently other techniques were applied including the use and measurement of enzyme activities, spectrophotometry , electrophoresis and immunoassay .

Introduction cont: 

Introduction cont Most current laboratories are now highly automated and use assays that are closely monitored and quality controlled

Introduction cont.: 

Introduction cont. Tests that require examination and measurement of the cells of blood, as well as blood clotting studies, are not included as in the UK these are usually grouped under hematology , but in many countries these specialties along with immunology and microbiology are grouped under laboratory medicine.

Introduction cont.: 

Introduction cont. All biochemical tests come under chemical pathology. These are performed on any kind of body fluid , but mostly on serum or plasma . Serum is the yellow watery part of blood that is left after blood has been allowed to clot and all blood cells have been removed.

Introduction cont.: 

Introduction cont. This is most easily done by centrifugation which packs the denser blood cells and platelets to the bottom of the centrifuge tube, leaving the liquid serum fraction resting above the packed cells. Plasma is essentially the same as serum, but is obtained by centrifuging the blood without clotting. Plasma therefore contains all of the clotting factors, including fibrinogen .

Introduction cont.: 

Introduction cont. A large medical laboratory will accept samples for up to about 700 different kinds of tests. Even the largest of laboratories rarely do all these tests themselves and some need to be referred to other labs.

Introduction cont.: 

Introduction cont. This large array of tests can be further sub categorised into sub-specialities of: General or routine chemistry Endocrinology - the study of hormones Immunology - the study of the immune system and antibodies Pharmacology or Toxicology - the study of drugs

Common chemical pathology tests include:: 

Common chemical pathology tests include: Electrolytes Sodium ; Potassium ; Chloride ; Bicarbonate ;

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Renal (Kidney) Function Tests Creatinine ; Blood urea nitrogen ; Urate

Common chemical pathology tests include:: 

Common chemical pathology tests include: Liver Function Tests Total protein ; Albumin ; Bilirubin ; direct; indirect; total AST ; ALT ; GGT ; ALP ;

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Cardiac Markers Troponin Myoglobin CK-MB ANP (A type Natriuretic peptide)

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Minerals Calcium ; Phosphate ; Magnesium ;

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Blood Disorders Iron ; Transferrin ; TIBC Vitamin B12 Folic acid

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Lipids profiles Cholesterol TG HDL-cholesterol VLDL-cholesterol LDL-cholesterol

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Hormones Testosterone Prolactin Progesterone Estrogen LH FSH TSH T3,T4

Common chemical pathology tests include: cont.: 

Common chemical pathology tests include: cont. Miscellaneous Globulins ; Glucose ; C-reactive protein ; Glycated hemoglobin (HbA1c). Arterial blood gases Stone analysis(Renal and Gall stones)

Solute and solvent: 

Solute and solvent In a solution, solvent is defined as the base substance, wherein the solute is being dissolved. While a solute is a substance that is dissolved into the solvent. It is not mandatory that a solution should be made up of only one solute and one solvent. In short, a solution can be prepared by combining two or more substances, provided the solutes are dissolving in the solvents.

Solute, Solvent, and Solution cont. : 

Solute, Solvent, and Solution cont. It is important to distinguish between three closely related terms solute, solvent , and solution . Solute – The substance that dissolves to form a solution Solvent – The substance in which a solute dissolves Solution – A mixture of one or more solutes dissolved in a solvent

Solute, Solvent, and Solution cont.: 

Solute, Solvent, and Solution cont. The following rules can be used to decide which component of a solution is the solute and which is the solvent. There are three states of matter: solids, liquids, and gases. Any reagent that undergoes a change in state when it forms a solution is the solute . If neither reagent changes state, the reagent present in the smallest amount is the solute .

Guidelines on Standard Operating Procedures for CLINICAL CHEMISTRY: 

Guidelines on Standard Operating Procedures for CLINICAL CHEMISTRY General introduction: Health care delivery is no longer a simple process of examining the patient and giving him a prescription. Over the years there has been rapid expansion in the various branches of health care services. As part of this expansion process and explosion of scientific medical knowledge, laboratory diagnosis has gained tremendous importance in today's practice

General introduction cont.: 

General introduction cont. Through the use of quality control (QC) the laboratory can ensure that the results being issued by it are reliable enough to allow decisions to be taken with confidence. QC is the study of those errors which are the responsibility of the laboratory, and of the procedures used to recognize and minimize them.

General introduction cont.: 

General introduction cont. Incorrect laboratory results may lead to wrong management decisions with possible fatal results. The reliability of laboratory results is therefore most important. It is not sufficient to ‘ think’ that ‘ my’ results are satisfactory. This has to be proved with scientific evidence.

General introduction cont.: 

General introduction cont. Laboratory personnel must know that QC is an obligation to the patient, that it is designed to give the analyst confidence in the methods used and that its purpose is not to find scapegoats or to punish those making mistakes

  Quality Manual : 

Quality Manual Towards achieving quality, international accreditation programmes strongly recommend the production of a quality manual by the laboratory. The quality manual of a laboratory is a document or a set of documents describing the organizational structure, responsibilities, procedures and processes by which the laboratory achieves its objectives and gains confidence in its work

  Quality Manual cont.: 

Quality Manual cont. .The manual is indispensable for achieving and maintaining good overall quality. Furthermore, the preparation of a quality manual may induce the laboratory to improve quality. Even a non-mandatory quality manual may be a valuable document for a clinical laboratory in demonstrating to clinicians and the hospital administration a commitment to quality.

Quality Manual cont.: 

Quality Manual cont. "The laboratory shall define and document its policies and objectives for, and its commitment to, good laboratory practice. The hospital management shall ensure that these policies and objectives are documented in the quality manual and communicated to, understood by, and implemented by all laboratory personnel concerned. The quality manual contents are as follows

Contents of quality manual : 

Contents of quality manual These are: Quality Policy and Quality System Organization Quality Control Personnel Accommodation and Environment Equipment Reference Materials Test Procedures Handling of Reagents Sample Collection, Storage and Disposal Maintenance of Records Laboratory Reports and Despatch of Reports

Quality policy: 

Quality policy The aim of the laboratory is to provide clinically useful information through laboratory measurement of samples from patients, taking into account the allocated resources. The quality policy is implemented by the following means; (2) Proper sample collection, stabilization, transport, sample preparation and identification.

Quality policy cont.: 

Quality policy cont. Reliable analytical work so that systematic and random errors do not exceed specified limits. Turn-around time within specified limits for routine and emergency measurements, and for rare routine measurements.

Quality policy cont.: 

Quality policy cont. Data reported in a clear form and supplemented with relevant information, including reference intervals to allow reliable clinical interpretation. Appropriate communication to the clinicians so that the results will be interpreted correctly and logically integrated into further (clinical and laboratory) evaluation of the patients, and that the clinicians become aware of unexpected problems and errors

Standard operating procedures    : 

Standard operating procedures The preparation of test procedures comes under the broad heading of Standard Operating Procedures (SOPs). SOP is a clear, concise and comprehensive written instruction of a method or procedure which has been agreed upon and authorized as the operating policy of the department.

PowerPoint Presentation: 

In general, SOPs, which mainly contain detailed descriptions of each analytical method, are essential for maintaining the same analytical quality over a long period of time. The procedures are a prerequisite to correct transfer of methods from one laboratory to another.

The contents of SOP are as follows: : 

The contents of SOP are as follows: Introduction Principle of method Specimen types, collection and storage Reagents, standards and control - preparation and storage Equipment, glassware and other accessories Detailed procedure Calculations, calibration curve

The contents of SOP are as follows: cont. : 

The contents of SOP are as follows: cont. Analytical reliabilities – (QC and Statistical assessment) Hazardous reagents Reference range and clinical interpretation

The contents of SOP are as follows: cont.: 

The contents of SOP are as follows: cont. Limitations of method (e.g. interfering substances and troubleshooting) References Date and signature of authorization (Effective date + Schedule for review)

Laboratory errors : 

Laboratory errors Analytical errors are classified into random errors and systematic errors. It is clear that random errors indicate poor precision while systematic errors indicate poor accuracy. A few examples of random errors are pipetting error, transcription error, wrong sample numbering and labelling, and fluctuating readings on the colorimeter

Laboratory errors cont.: 

Laboratory errors cont. . Systematic errors could occur due to wrong procedure, incorrect standard and calibration procedure. Errors can occur in any of the limb of the cycle of events taking place in a hospital, starting from the physician examining the patient and back to the physician (pre-analytical/ analytical/post-analytical).

Laboratory errors cont.: 

Laboratory errors cont. The physician, after examining the patient, decides and orders a test, and collects and transports the patient’s samples; this constitutes the pre-analytical limb of the cycle of events. In the analytical limb the sample is received by the laboratory and analysed. The post-analytical limb consists of the transfer of the result to the physician and a meaningful interpretation of the laboratory data by the physician, followed by necessary action.

   Definition: : 

Definition: Accuracy is the degree of agreement between a measured value and its ‘true/consensus’ value. On the contrary, inaccuracy, which is represented by analytical bias, is defined as the % of the difference between the measured value and the ‘true’ value over the true value. Therefore , good accuracy means least analytical error.

   Definition:: 

Definition: Precision refers to reproducibility. It refers to the agreement between replicate measurements. It is quantitatively expressed as the standard deviation (SD) or more precisely as percent coefficient of variation (CV), which is defined as SD times 100 divided by the mean value of the results in a set of replicate measurements. Therefore, good precision means least CV.

     Pre-analytical : 

Pre-analytical The pre-analytical system shall take care of the following aspects (3) ,as each can have a major effect on the accuracy of the result: Patient preparation Request forms

     Pre-analytical cont.: 

Pre-analytical cont. Specimen collection, containers, labelling and phlebotomy equipment and procedure Specimen transport Specimen preparation Specimen storage

  Analytical: 

Analytical The following aspects(3) shall be monitored, evaluated, implemented and maintained to ensure the accuracy and precision of the test carried out: Quality of distilled water Calibration of measuring and testing instruments including balances, thermometers, incubators, waterbaths , autoclaves, centrifuges and semi-automatic pipettes, and regular servicing and maintenance of equipment.

Analytical cont.: 

Analytical cont. It is essential to use a standard calibrator which is traceable to national/international reference material. The laboratory shall obtain evidence of traceability to the reference material from the supplier. Precision can be maintained through the use of suitable QC material, either commercial or prepared in-house.

Analytical cont.: 

Analytical cont. The QC material should be analysed at predetermined intervals along with patient samples to monitor systematic and random errors. Such QC material shall also be traceable to a national/international certified reference material so that the accuracy of measurements can be monitored.

Analytical cont.: 

Analytical cont. All data relating to the laboratory’s internal QC practices and performance in external quality assessment schemes (scoring, ranks, etc.) shall be recorded, reviewed and corrective actions implemented.

Analytical cont.: 

Analytical cont. Stability of reagents Laboratory personnel should be aware that the stability of all reagents kept at room temperature will go down from the stated values if the temperature exceeds 35 0 C.

Analytical cont.: 

Analytical cont. Use of calibration graphs A fresh standard curve should be carried out for the analyses described in this manual whenever: the calibrator is changed new reagents are introduced problems with QC are encountered

   Post-analytical: 

Post-analytical In order to avoid transcriptional errors in the results of the test, the reporting/signatory technicians shall verify the results entered manually or through on-line instrument interfaces before the results are reported or despatched.

Rectification of laboratory errors: 

Rectification of laboratory errors It is therefore essential to continually ask the following questions. Is there an analytical error? If so, what type of error is this? What could have been the causes for this error? How to rectify this error?

Rectification of laboratory errors cont.: 

Rectification of laboratory errors cont. It is important to identify analytical errors and classify them as either random or systematic errors. Towards this end, the laboratory should implement internal QC procedures. This involves preparation of a QC pool, either human or bovine, quantification of unavoidable laboratory errors, construction of Levey -Jennings chart and daily analysis of QC along with every batch of patients’ samples .

Homework: 

Homework Photometry Fluorometry – Nephelomety and Turbidimetry Osmometry Theory or electrophoresis Chromatography Colormeters Spectrophotometer /types Ion selective electrode Flame photometers