Chapter 20 Laboratory Assistant Skills Copyright 2017 Cengage

Chapter 20 Laboratory Assistant Skills Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 1 Operating the Microscope • Instrument used to magnify and visualize objects too small for human eye • Monocular microscope: one eyepiece • Binocular microscope: two eyepieces • Quality varies • Refer to Procedure 20: 1 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 1 Operating the Microscope • Compound, bright-field microscope is commonly used • Epifluorescence microscope – Used with fluorescent dye stain • Electron microscope – Used to view extremely small objects Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 1 Operating the Microscope • Microscope parts (refer to Figure 20 -2 in Text) – Base – Arm – Eyepiece(s) – Objectives – Revolving nosepiece – Stage Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 1 Operating the Microscope • Microscope parts – Coarse adjustment – Fine adjustment – Condenser and iris diaphragm – Illuminating light – Body tube Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 2 Obtaining and Handling Cultures • Culture specimen is obtained when physician wants to identify causative agent of a disease • Sample specimen is examined right away or grown and then examined • Sterile collection container and swab to collect culture • Container with proper medium for culture Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 2 Obtaining and Handling Cultures • Direct smear or bacteriological smear • Agar plate (culture plate, petri dish) or culture media tube • Culture and sensitivity (C&S) study – Resistant organisms – Sensitive organisms Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 2 Obtaining and Handling Cultures • Fixing a slide • Gram’s stain technique – Gram positive, gram negative • Rapid identification tests for common bacteria • Use standard precautions • Refer to Procedures 20: 2 A– 20: 2 E in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 3 Puncturing the Skin to Obtain Capillary Blood • Blood tests used to assist physicians in making diagnoses • Responsibility for obtaining blood for blood tests varies – Check your state regulations – Always know what you are permitted to do Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 3 Puncturing the Skin to Obtain Capillary Blood • Types of blood draw – Skin puncture – Venipuncture – Arterial blood • Follow careful aseptic technique • Refer to Procedure 20: 3 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 3 Puncturing the Skin to Obtain Capillary Blood • Know common puncture sites (refer to Figure 20 -15 in Text) • Placement of skin puncture • Always remove first drop of blood • Procedure after puncture specimen obtained • Always use standard precautions Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 4 Performing a Microhematocrit • Also called HCT or “crit” • Measures volume of packed red blood cells (RBCs), or erythrocytes, in blood – Erythrocytes carry oxygen from lungs to body and carbon dioxide from body cells to lungs • Described as percentage of RBCs per volume of blood Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 4 Performing a Microhematocrit • Different methods • Microhematocrit requires less blood and takes less time than other methods • Centrifuge separates blood into RBCs, buffy coat, and plasma • Leukocytes (white blood cells) fight infection Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 4 Performing a Microhematocrit • Anticoagulants and special capillary tubes • Normal values vary slightly – Low hematocrit: anemia – High hematocrit: polycythemia • Physician must interpret test results for patient • Refer to Procedure 20: 4 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 5 Measuring Hemoglobin • Hemoglobin (Hgb) determines oxygen-carrying capacity of the blood • Hemolysis – Destruction of RBCs, release of hemoglobin • Hemoglobinometer – Measures hemoglobin concentration in blood Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 5 Measuring Hemoglobin • Disposable cuvette, test slide, or test strip with hemolyzing solution used to obtain blood sample • Normal values vary by test type • Double-check readings for accuracy • Physician must interpret test results • Refer to Procedure 20: 5 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 6 Preparing and Staining a Blood Film or Smear • Prepared by placing small drop of blood on a slide, then spreading blood in thin layer using another slide, coverslip, or spreader • Uses of blood film or smear – Differential count of WBCs – Examine erythrocytes Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 6 Preparing and Staining a Blood Film or Smear • Equipment must be extremely clean • Cells must be stained for microscope viewing – Wright’s stain – Quick stain (three-step method) • Follow manufacturer’s instructions • Refer to Procedures 20: 6 A– 20: 6 B in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 7 Testing for Blood Types • Blood types inherited from parents • Type of blood determined by presence of antigens on red blood cells • Antigen causes production of antibody – ABO blood type system – Rh system Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 7 Testing for Blood Types • Blood types – Type A contains antigen A on RBCs – Type B contains antigen B on RBCs – Type AB contains antigens A and B of RBCs – Type O contains neither antigen on RBCs • Rh type and antigen-antibody reaction Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 7 Testing for Blood Types • • Blood typing and crossmatch Blood banks also do antibody screen Hemolytic disease of the newborn (HDN) Blood typing with anti-serums (refer to Figure 20 -28 and Procedure 20: 7 in Text) Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 8 Performing an Erythrocyte Sedimentation Rate • Erythrocyte sedimentation rate (ESR) – Measures distance red blood cells fall and settle in a special glass test tube in a specific period of time – Also called sedimentation rate or sed rate • Must be performed at room temperature • Special rack used for ESR Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 8 Performing an ESR Measurements taken at specific time periods Wintrobe or Westergren methods Normal values can vary slightly Abnormal rates may indicate inflammation, polycythemia, and other diseases • Refer to Procedure 20: 8 in Text • • Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 9 Measuring Blood Sugar (Glucose) Level • • Glucose Form of sugar found in bloodstream Insulin allows metabolism of glucose Insufficient insulin: diabetes mellitus – Hyperglycemia, glycosuria – Treated with diet, insulin injections Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 9 Measuring Blood Sugar (Glucose) Level • Tests for glucose level – Fasting blood sugar (FBS) – Glucose tolerance test (GTT) – Glycohemoglobin test (Hb. A 1 C or Hb. A 1) Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 9 Measuring Blood Sugar (Glucose) Level • Diabetics used urine tests to check level of glucose – Urine tests are not as accurate because kidney function varies between individuals • Most diabetics use blood testing now – Reagent strips for rapid blood testing Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 9 Measuring Blood Sugar (Glucose) Level • Proper storage of reagent strips • Proper use and care of glucose meter • Most diabetic patients—even children— monitor their own blood sugar levels • Refer to Procedure 20: 9 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 10 Testing Urine • Often done to determine physical condition of patient • Abnormal urine tests are often the first indication of a disease process • Know normal and abnormal characteristics of urine (refer to Table 20 -1 in Text) Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 10 Testing Urine • Urinalysis: physical, chemical, and microscopic texting of urine • Physical testing of urine includes – Color – Transparency —Odor —Specific gravity Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 10 Testing Urine • Chemical testing of urine includes – – Ph Protein Glucose Ketone – Bilirubin – Urobilinogen – Blood Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 10 Testing Urine • Microscopic testing of urine includes – Cells – Casts – Crystals – Amorphous deposits Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 10 Testing Urine • Collection of urine in specimen containers • Urine should be fresh and warm for more accurate results – Examined within 1 hour or refrigerated • Follow standard precautions Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 11 Using Reagent Strips to Test Urine • Read and follow manufacturer’s directions • Reagent strips contain chemical reactants that react to a specific substance – If the substance is present, the reagent strip changes color • Store reagent strips properly Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 11 Using Reagent Strips to Test Urine • Reagent strips test for – Ph – Protein – Glucose – Ketones/acetones —Blood —Bilirubin —Urobilinogen —Phenylalanine • Many different reagents strips are available Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 11 Using Reagent Strips to Test Urine • Color comparison chart on or with bottle • Daily quality-control checks • Automated strip readers – More accurate but expensive • Record results of test properly • Refer to Procedure 20: 11 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 12 Measuring Specific Gravity • Specific gravity – Measurement of concentration of urine • Low specific gravity of urine – Below 1. 005; diluted urine • High specific gravity of urine – Above 1. 030; concentrated urine Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 12 Measuring Specific Gravity • Measurement with a urinometer • Measurement with a refractometer or digital refractometer – Test for accuracy before use • Refer to Procedure 20: 12 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 13 Preparing Urine for Microscopic Examination • To examine urinary sediment – Certain substances indicate disease conditions • Fresh, first-voided, early morning specimen preferred – Most concentrated specimen Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 13 Preparing Urine for Microscopic Examination • Only a portion of urine specimen is examined • Size of drop of concentrated urine examined is important • Urinary sediment should be examined immediately after placement on a slide Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

20: 13 Preparing Urine for Microscopic Examination • Identification of substances present – Refer to Figure 20 -43 in Text – Requires training and experience • Must be legally qualified to examine sediment • Refer to Procedure 20: 13 in Text Copyright © 2017 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.