Intro to Diagnostic Imaging 2024 copy.pdf

Basic Lab Tests: Overview Rebecca Muller, PA-C, MSPAS August 8, 2024 Objectives Explain how specificity and sensitivity may be applied to diagnostic testing Locate the normal values associated with a complete blood count (CBC) with and without differential, blood cultures, basic...

Basic Lab Tests: Overview Rebecca Muller, PA-C, MSPAS August 8, 2024 Objectives Explain how specificity and sensitivity may be applied to diagnostic testing Locate the normal values associated with a complete blood count (CBC) with and without differential, blood cultures, basic metabolic panel (BMP), comprehensive metabolic panel (CMP), urinalysis (UA), and urine pregnancy test (UPT) Describe what each component of these tests are, and to which test they are a part Determine how each test is collected and how information is gleaned from each blood sample Apply when these tests can be utilized in a clinical setting and understand examples of when they can be used (e.g. BUN used to determine kidney function)  Outline Diagnostic Testing Sensitivity and Specificity Complete Blood Count (CBC) CBC with Differential Blood Cultures Basic Metabolic Panel (BMP) Comprehensive Metabolic Panel (CMP) Urine Tests Diagnostic Testing Tests that help a provider to determine information about patient’s problem Point of care testing Tests that can be resulted outside of a clinical laboratory E.g. POC glucose testing  Sensitivity Test’s ability to identify patient’s with disease E.g. In a group of patients who have +strep test, how many of those patients have strep Clinically applied: Tests with high sensitivity help provider have high confidence when (-) that patient truly does not have disease  Specificity Test’s ability to identify patient’s without disease E.g. In a group of patient’s who have (–)strep tests, how many truly did not have strep Clinically applied: Tests with high specificity help provider have high confidence when + that patient truly has disease Clinically Applying Complete Blood Count (CBC)  Test Range WBC 4500-11,000/mm3 (4.5 – 11 x103) RBCmale 4.3 – 5.9 million/mm3 RBCfemale 3.5 – 5.5 million/mm3 Hgbmale 13.5 – 17.5 g/dL Hgbfemale 12 – 16 g/dL CBC Hctmale Hctfemale 41- 53% 36 - 46% MCV 80 – 100 μm3 MCH 25.4 – 34.6 pg/cell MCHC 32 – 36 g/dL RDW 11.5 – 14.5% Platelets 150,000 – 400,000/mm3  Documentation med students will write this before rounds fish-bones https://upload.wikimedia.org/wikipedia/commons/c/cb/Hematology_Fishbone_Schematic.png?20130716075104 Formed Elements of Blood Plasma White blood cells (WBC) Red blood cells (RBC) Platelets https://upload.wikimedia.org/wikipedia/commons/1/1d/Blausen_0425_Formed_Elements.png  CBC White blood cell count  WBC or leukocyte count Leukocytosis vs leukopenia Red blood cell count  RBC or erythrocyte count Erythrocytosis vs erythrocytopenia Hemoglobin  Hgb Amount of hemoglobin in the blood Hematocrit  Hct % blood volume which contains erythrocytes Platelets  thrombocytes Thrombocytosis vs thrombocytopenia Size and Shape of Erythrocytes – Indices Mean Corpuscular Volume  MCV **size** Average size of RBC Based on this can further classify cells: Macrocytic Microcytic Normocytic Mean Corpuscular Hemoglobin Concentration  MCHC **color** Average amount of hemoglobin per volume within each individual RBC When outside range further classify cells as: Hyperchromic Hypochromic Size and Shape of Erythrocytes – Indices Mean Corpuscular Hemoglobin  MCH Amount of hemoglobin present in a cell Red Blood Cell Distribution Width  RDW Average width of RBC Indices: Clinical Significance For example: Determining kind Microcytic, hypochromic anemia of anemia E.g. Iron deficient anemia Collection Collected via peripheral venous puncture Must be collected in a special tube that contains EDTA (anticoagulant) Blood spun in centrifuge to separate components Plasma Buffy coat (WBCs and platelets) antecubital fossa RBCs https://www.flickr.com/photos/nihgov/29466760926 CBC with Differential  Test Normal Values Segmented 54 – 62% Neutrophils Bands 3 – 5% Differential Eosinophils 1 – 3% Basophils 0 - 0.75% Lymphocytes 25 – 33% Monocytes 3 - 7%  CBC w Diff Differential is an additional order to a CBC Differential  percentages of different types of WBCs Neutrophils Bands Lymphocytes Monocytes Eosinophils Basophils White Blood Cells Neutrophils Acute infection and inflammatory response Bands Acute infection (new neutrophils) baby neutrophils Eosinophils Parasitic infections Allergic reactions Basophils Hypersensitivities Lymphocytes Viral infections Monocytes Chronic infections, late phase infections White Blood Cells https://byjus.com/full-form/wbc-full-form/ Collection Same as CBC Two types of counting methods for cells Manual differential Automated differential Blood Cultures  Normal Values “No growth after…hours” Requires inoculation Takes 3-5 days for final result depending on organisms being tested  Clinical Indication BACTEREMIA Infection in the blood Possible causes of bacteremia: Sepsis Endocarditis Meningitis Septic arthritis Infection from an implantation (cardiac device, intracranial device, etc) Collection Both an anaerobic bottle and aerobic bottle should be obtained Two sets of cultures are collected at the same time Different sites are used for each set of cultures Helps to rule out contamination of skin bacteria Collected prior to antibiotic administration Collection Blood culture bottles contain culture media Inoculated in a lab for up to 5 days MOST bacteria will grow within 24-48 hours Fungus takes longer to grow (~5 days) If positive additional testing performed to obtain sensitivity of bacteria to antibiotics/antifungls Susceptibility Testing If growth is found on the culture media further testing is required Susceptibility testing  exposure of media to antibiotics to determine which medication organism is susceptible to Susceptibility Testing Results https://clsi.org/about/blog/ast-news-update-2019-case-study/ MIC  minimum inhibitory concentration Smallest amount of antibiotic that is needed to kill the organism Basic Metabolic Panel (BMP)  Test Abbreviation Value Sodium Na 136 – 145 mEq/L Potassium K 3.5 – 5.0 mEq/L Chloride Cl 95 – 105 mEq/L Bicarbonate HCO3 22- 28 mEq/L BMP Glucose Fasting Glu 70 – 99 mg/dL 2 hr postprandial < 120 mg/dL Blood Urea Nitrogen BUN 7-18 mg/dL Creatinine Cr 0.6 – 1.2 mg/dL Glomerular Filtration Rate GFR >60 mL/min/1.73 m3  Fishbones https://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Electrolyte_diagram.png/1200px-Electrolyte_diagram.png?20120712182759  Clinical Indication Electrolyte Volume status Acid/base Nutrition Renal status status status function  Sodium (Na) Maintains hydration in the tissues Hyponatremia/hypernatremia Potassium (K) Protein synthesis and muscle contraction Hypokalemia/hyperkalemia Electrolytes Chloride (Cl) Maintains cellular electrical neutrality Hypochloremia vs hyperchloremia Glucose (Glu) Important for energy Hypoglycemia vs hyperglycemia  Bicarbonate (HCO3) Participates in acid-base equilibrium of the body Estimate of the CO2 in the body Most accurate way to assess is with an arterial blood gas (different type of test requiring analysis of arterial vs venous blood) Increased levels indicate alkalosis (high pH) Decreased levels indicate acidosis (low pH)  Blood Urea Nitrogen (BUN) Urea is the waste product produced by protein metabolism Kidney’s job is to filter this out Kidney damage/pathology will result in higher levels of BUN  Creatinine (Cr) Creatinine phosphate produced as byproduct when skeletal muscles contract Kidney damage/pathology will result in higher levels of Cr  Glomerular Filtration Rate (GFR) A calculation based on Cr, age, sex, ethnicity (Modification of Diet in Renal Disease Study Equation) Used to help determine kidney function Many medications are renally cleared and so used for pharmacologic dose adjustments Mosby’s  Collection Peripheral venous puncture Collected in a tube without anticoagulant to evaluate serum BMP is evaluated by serum Plasma without clotting factors No blood products  ability to evaluate other components in blood such as electrolytes https://www.majordifferences.com/2018/07/difference-between-blood-serum-and.html Comprehensive Metabolic Panel (CMP)  Test Normal Value Albumin 3.5-5.5 g/dL Total Protein 6.0-7.8 g/dL Total Bilirubin 0.1-1.0 mg/dL Aspartate 8-20 U/L CMP (minus BMP) Aminotransferase (AST) Alanine Transaminase 8-20 U/L (ALT) Alkaline Phosphatase 20-70 U/L Calcium 8.4-10.2 mg/dL  CMP Everything in a BMP and the following tests Albumin Total protein Bilirubin (total) Transaminases Aspartate aminotransferase (AST) Alanine aminotransferase (ALT) Alkaline phosphate Calcium (Ca)  Albumin and Total Protein Total protein Total measure of protein in the serum ~60% of this is albumin, but also includes prealbumin and globulins Albumin Protein made in the liver Helps to maintain intravascular pressure Transports metabolites (e.g. drugs and hormones) throughout the body  Bilirubin Product of red blood cell catabolism Bilirubin production occurs in multiple organs, including liver Different values associated with each area of catabolism: total, direct, indirect Total bilirubin = indirect + direct Total bilirubin is the only value included in CMP Hyperbilirubinemia/hypobilirubinemia  Aspartate aminotransferase (AST) Enzyme present in skeletal, cardiac, and liver cells After injury occurs, AST will leech into blood stream Alanine aminotransferase (ALT) Enzyme present in liver cells After injury ALT leeched into blood stream Liver Enzymes Alkaline phosphatase Enzyme present in liver, bone, and biliary tract Enzyme found in multiple systems can give information about pathology/physiology in multiple systems E.g. increased alk phos in children whose bones are growing  Calcium exists in the body bound to albumin and floating in serum Ionized calcium is floating in serum (~50% total) Bound to albumin ~50% Calcium (Ca) Ca in a CMP is the total amount of Ca (including both ionized and bound) To assess ionized Ca (free-floating Ca) can order a specific test, or use a calculation Corrected Calcium mg/dL = (0.8 * (Normal Albumin - Pt's Albumin)) + Serum Ca  Collection Peripheral venous puncture Values are evaluated via serum Different institutions have different CMP values that are reported, but generally includes: Liver function tests Total bilirubin Ca Urine Tests  Tests Normal Values Appearance Clear Color Yellow pH 4.6-8.0 Proteinmale 0-60 mg/24 hrs Proteinfemale 0-90 mg/24 hrs Specific Gravity 1.002-1.028 Urinalysis Leukocyte Esterase Nitrites Negative Negative Ketones Negative Bilirubin Negative Urobilinogen 0.1-1.8 mg/dL Glucose Negative WBC 0-4 RBC ≤2  Tests run include Physical Chemical Microscopic Screening tools Metabolic disorder Renal/urinary disorder Infectious disorder Inflammatory disorder Hepatic disorder Hemolytic disorder Multiple tests run: Appearance/color pH Protein Specific gravity Leukocyte esterase Nitrites Urinalysis Ketones Bilirubin Urobilinogen Glucose WBC RBC  pH Determine acid/base status of a patient NB. Many things can affect pH of urine (e.g. medications and food) pH and Specific Aid in determination of type of renal stone Gravity Specific gravity Measurement of how heavy urine is compared to distilled water E.g. Higher when glucose or protein in urine  Should all be negative Proteinuria Occurs in kidney/autoimmune pathology and can be seen in disorder of pregnancy Protein, Glucose, Glucosuria Ketones Occurs with some diabetic medication use and hyperglycemia Ketonuria Occurs from fatty acid catabolism (e.g. can occur in state of severe hyperglycemia  DKA)  Bilirubin can be present from state of hyperbilirubinemia Bilirubin and Should be negative Urobilinogen Normal breakdown of urobilinogen leads to a small amount of excretion via kidney  Leukocyte Esterase Positive when broken and intact leukocytes detected in the urine Leukocyte Esterase Nitrites Positive when bacteria present in urine and Nitrites Bacteria produce an enzyme that converts nitrates to nitrites Often interpreted together to determine whether a urinary tract infection is present Urine Microscopy Presence of WBCs and RBCs in urine may indicate: Urinary tract infection Renal stone Contaminant from other organ (e.g. vaginitis, menses, skin cells from surrounding organs, etc) https://tidsskriftet.no/en/2014/09/perspectives/urine-microscopy-important-diagnostic-tool  Qualitative test for pregnancy +/- Detects human chorionic gonadotropin (HCG) in urine HCG secreted by placental trophoblast after conception Urine Pregnancy Test HCG levels may not be detectable in urine until ~2 weeks depending on the test **In people with vulvas ALWAYS be thinking about the possibility of pregnancy**  References 1. Doern GV. Detection of Bacteremia: Blood Cultures and other diagnostic tests. UpToDate. Accessed August 28, 2023. https://www.uptodate.com/contents/detection-of-bacteremia-blood-cultures-and-other- diagnostic- tests?search=blood+cultures&source=search_result&selectedTitle=1~150&usage_type=default&display _rank=1. 2. Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Tests Reference. 16th ed. Elsevier; 2023. 3. Slide deck adapted from Victoria Miller, PA-C 4. Cavallazzi R, Bennin CL, Hirani A, Gilbert C, Marik PE. Is the band count useful in the diagnosis of infection? An accuracy study in critically ill patients. J Intensive Care Med. 2010 Nov-Dec;25(6):353-7. doi: 10.1177/0885066610377980. Epub 2010 Sep 13. PMID: 20837634. 5. Mark DB, Wong JB. Decision-Making in Clinical Medicine. In: Loscalzo J, Fauci A, Kasper D, Hauser S, Longo D, Jameson J. eds. Harrison's Principles of Internal Medicine, 21e. McGraw-Hill Education; 2022. Accessed August 01, 2024. https://accessmedicine-mhmedical- com.jwupvdz.idm.oclc.org/content.aspx?bookid=3095&sectionid=261076027 6. https://www.medicinenet.com/what_does_urobilinogen_in_urine_indicate/article.htm 7. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.bristol.ac.uk/media- library/sites/vetscience/documents/clinical-skills/Urine%20Sediment%20Preparation.pdf 8. NCCPA “Normal Laboratory Values”