Unit 18 Laboratory Assistant Skills

18:1 Operating the Microscope Many different models Monocular microscopes – one eye piece Binocular microscopes – two eye pieces Quality varies Calculation of magnification Care and cleaning of microscope Basic principles for operating a microscope Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Types of Microscopes Compound, bright-field Epiflourescence Electron Purpose: magnify or enlarge objects so they become more visible Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Parts of a Microscope Base Arm Eyepieces or ocular viewpieces Objectives Revolving nosepiece Stage Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Parts of a Microscope (continued) Coarse adjustment Fine adjustment Iris diaphragm Illuminating light Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:2 Obtaining and Handling Cultures Obtained when doctor wants to identify the causative agent of a disease Sample specimen is either examined at that time or grown and then examined Use sterile applicator swab to collect specimen Keep specimen moist and free from contact with anything else Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Obtaining and Handling Cultures (continued) Direct smear or bacteriological smear Agar plate, culture plate, petri dish, culture media tube Culture and sensitivity Resistant organisms Sensitive organisms Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Obtaining and Handling Cultures (continued) Fixing a slide Gram’s stain Standard precautions Basic principles for obtaining a culture specimen Basic principles for preparing a direct smear Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Obtaining and Handling Cultures (continued) Basic principles for streaking an agar plate Basic principles for transferring culture from agar plate to slide Basic principles for staining with Gram’s stain Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:3 Puncturing the Skin to Obtain Capillary Blood Often used to assist physician in making a diagnosis Responsibility for obtaining blood for various blood test varies Check your state regulations Always know what you are permitted to do Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Methods of Obtaining Blood Skin puncture Venipuncture Arterial blood Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Skin Puncture Aseptic technique Common puncture sites Points to check prior to skin puncture Proper type of puncture Always remove first drop of blood After puncture specimen obtained Always use standard precautions Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:4 Performing a Microhematocrit Also called HCT or “crit” Measures volume of packed red blood cells (RBCs) or erythrocytes in the blood Often described as percentage of RBCs per volume of blood Different methods Microhematocrit centrifuge Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Performing a Microhematocrit (continued) Capillary tubes Normal values Abnormal readings Accuracy is essential Careful recording of tests Physician’s responsibility to report test results to patient Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:5 Measuring Hemoglobin Used to determine oxygen-carrying capacity of the blood Hemolysis Hemoglobinometer Automated photometer Normal values Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Measuring Hemoglobin (continued) Abnormal values Accuracy is essential Basic principles of using a hemoglobinometer Basic principles of using a photometer Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 18:6 Counting Blood Cells Erythrocyte and leukocyte counts are done to determine the number of blood cells in the blood Methods used Hemacytometer counting chamber Must dilute blood first Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Counting Blood Cells (continued) Microscopic powers used Normal values Accuracy is essential Basic principles for counting blood cells Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:7 Preparing and Staining a Blood Film or Smear Preparation of blood film or smear Uses of blood film or smear Equipment must be extremely clean Wright’s stain Quick stain (three-step method) Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Preparing and Staining a Blood Film or Smear (continued) Basic principles for preparing Basic principles for staining with Wright’s stain Basic principles for staining with a quick stain kit Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:8 Testing for Blood Types Blood types inherited from parents Type of blood determined by presence of certain factors called antigens on red blood cells Antigen ABO blood type system Rh type system Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Testing for Blood Types (continued) Antigen-antibody reaction Typing and crossmatch Hemolytic disease of the newborn (HDN) Using anti-serums for blood typing Basic principles for testing for blood types with anti-serum Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:9 Performing an Erythrocyte Sedimentation Rate (ESR) Measures the distance that red blood cells have fallen or settled to the bottom of a glass test tube in a specific period of time Also called sedimentation rate or sed rate Basic procedure for test Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Performing an ESR (continued) Special rack used for ESR Measurements usually taken at specific time periods Normal values can vary slightly Abnormal readings Basic principles for performing erythrocyte sedimentation rate Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:10 Measuring Blood-Sugar (Glucose) Level Glucose metabolism Diabetes mellitus Control of diabetes mellitus Fasting blood sugar (FBS) Glucose tolerance test (GTT) Glycohemoglobin test (HbA1C or HbA1) Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Urine Tests Previously, diabetics used urine tests to check level of glucose High glucose in urine would indicate high glucose in blood Urine tests are not as accurate because kidney function varies between individuals Most diabetics use blood testing now Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Blood Glucose Advantages of checking blood glucose versus urine glucose Testing blood with reagent strips Proper care of reagent strips Proper use and care of glucose meter Instructions to patients Basic principles for measuring blood-sugar/glucose level Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Summary Different blood tests are used to diagnose disease Accuracy is essential with any test Standard precautions must be observed at all times Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 18:11 Testing Urine Often done to determine physical condition of patient Abnormal urine tests are often the first indication of disease Important to know normal and abnormal characteristics of urine Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Testing Urine (continued) Volume Color Transparency Odor pH reaction Specific gravity Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Testing Urine (continued) Glucose Albumin or protein Acetones or ketones Blood Pus Bacteria Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Testing Urine (continued) Red blood cells (erythrocytes) White blood cells (leukocytes) Bilirubin Urobilinogen Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Urinalysis Examination of the urine Includes physical, chemical, and microscopic testing Physical examination usually done first Chemical testing Microscopic examination Urine should be fresh – more accurate Standard precautions Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:12 Using Reagent Strips to Test Urine Commonly used for chemical testing of urine Reagent strips Storage of strips Chemical reactants – note expiration Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Using Reagent Strips to Test Urine (continued) pH Protein Glucose Ketone or acetone Blood Bilirubin Urobilinogen Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Using Reagent Strips to Test Urine (continued) Types of reagent strips Automated strip readers or analyzers Read instructions carefully Fresh urine specimen should be used Record results of test correctly Basic principles of testing urine with reagent strips Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:13 Measuring Specific Gravity Specific gravity defined Low specific gravity of urine High specific gravity of urine Urinometer Refractometer Basic principles for measuring specific gravity Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

18:14 Preparing Urine for Microscopic Examination Purpose Fresh, first-voided morning specimen preferred Only portion examined Size of drop of concentrated urine examined is important Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Preparing Urine for Microscopic Examination (continued) Urinary sediment should be examined immediately Identification of substances present Basic principles for preparing urine Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.

Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED. Summary Substances present in urine are often first indication of disease Variety of urine tests performed to check for these substances Observe standard precautions while performing any urine tests Copyright © 2004 by Thomson Delmar Learning. ALL RIGHTS RESERVED.