Lab Data Interpretation PDF

Diagnostic Tests Hanan Muzeyin(B.Pharm, Msc) 1  Objectives At the end of this session, you will be able to:  Identify the different diagnostic modalities used in clinical practice  Differentiate abnormal lab values from normal (refer...

Diagnostic Tests Hanan Muzeyin(B.Pharm, Msc) 1  Objectives At the end of this session, you will be able to:  Identify the different diagnostic modalities used in clinical practice  Differentiate abnormal lab values from normal (reference ones)  Interpret different laboratory results of a patient  Monitor patient response using laboratory values  Identify drugs that will interfere with normal lab values  Devise treatment strategy and develop pharmaceutical care plan based on patient lab investigations 2 Diagnostic Tests (General principles) Diagnostic test findings  should be used to compliment other subjective and objective findings.  and must not be evaluated in isolation.  Diagnostic test findings can be helpful  in assessing clinical disorders  establishing a diagnosis,  evaluating disease progression and assessing drug therapy  The findings must be assessed in the context of the clinical situation since different factors affect the test results. 3  Diagnostic Tests(General principles) Which factors affect lab values? – Patient factors, Lab factors, human factors Normal values may vary from laboratory to laboratory, techniques and reagents Drugs (masking) – Amitriptyline (blue green urine) – Rifampin (orange urine) Normal values may also vary depending on the patient's – age (organ function); gender (Hgb), weight/height (SCr), and other factors.  Diagnostic Tests(General principles) Laboratory error – technical error, improper calculation, inadequate specimen, incorrect sample timing, improper sample preservation, food or medication interference with laboratory tests. – If laboratory error is suspected, the test should be repeated. Remember: ALWAYS Treat the Patient not the Lab Value!  Diagnostic Tests(General principles) Reference Ranges vs Normal Range  The term reference range is preferred in clinical practice several factors contribute to the “normal” value for each individual. Test Reliability Indicators of test reliability include accuracy, precision, sensitivity, and specificity. Precision: refers to the repeatability of a laboratory test  (i.e., test results fall within a similar value when repeated)  Accuracy: the ability of a test to provide a result that is reflective of the “true” value  (i.e., the test result matches the actual real value). 6  Diagnostic Tests(General principles) Quality control and assurance practices at each laboratory are monitored regularly to ensure reliability of results. Typically, if a result is obtained that is significantly outside the reference range, the laboratory will repeat the test to confirm or refute the finding. Research studies generally establish the sensitivity and specificity of laboratory tests. Clinically these are essential to distinguish the presence or absence of a disease or condition. 7  Diagnostic Tests(General principles) Sensitivity: the ability of the test to correctly identify the disease or condition.  If a test is 95% sensitive, then 95% of the individuals will be correctly identified as having the disease or condition, but 5% will have a negative test result even though they have the disease or condition (false negative). Specificity: the ability of the test to rule out individuals who do not have the disease or condition.  If a test is 95% specific, then 95% of the individuals without disease will have a correct negative result, but 5% will be identified as having the disease or condition even though they are negative (false positive). 8  Diagnostic methods A. Biochemical methods B. Physical methods Blood tests 1. Mechanical  Enzyme tests Blood pressure  Test for evaluation of serum Body temperature concentration - Na, K, measurement Ca..., glucose, Urea Auscultation  Organ function test Palpation Urine & other bodily fluid analysis Percussion 9  Diagnostic methods 2. Electrical 6. X- ray Imaging ECG, EEG, Audiometry... Computer tomo-graphy 3. Electromechanical (CT), CXR….. Spirometry 7. Methods of Nuclear 4. Optic and Optoelectric Medicine Light microscopy, Electron Radioi-sotopes , microscopy, Ophtalmoscopy, Gammagraphy, Positron Otoscopy, Bronchoscopy... Emmision Tomography (PET).... 5. Ultrasound (Dopplers) Blood flow test, Sonography, 8. Magnetic scanning Nuclear Magnetic Echocardiography... Resonance Tomography (NMRT) 10  Diagnostic Tests- Microbiology Microbiologic Studies Direct examination of a specimen (eg, sputum, blood, or urine) may aid in a presumptive diagnosis. Microbial cultures are obtained with a Gram stain of the cultured material. A Gram stain of collected specimens can give rapid information that can be applied immediately to patient care. Gram Stain Developed in 19th Century for distinguish and classify bacterial species. 11  Diagnostic Tests- Microbiology Gram Stain Three classifications – color; shape & organization Color - Two classes of bacteria – Gm +ve – stain purple – Gm –ve stain pink or red – Bacteria indwelling intracellularly…? Chlamydia, Mycobacterium (without cell wall) identified by alternative staining techniques Shape – Cocci (round); Bacilli (rod) Organization – Pairs or clusters; chains  Culture and susceptibility Culture and susceptibility testing provides additional information to the clinician to select appropriate therapy. Specimens are placed in or on culture media that provide proper growth conditions.  Once the bacteria grow on culture media, they can be identified through biochemical tests.  When a pathogen is identified, susceptibility tests can be performed to various antimicrobial agents. Reported as: Sensitive (S) vs Intermediate (I) vs Resistant (R) 14 Diagnostic Tests: Hematology 15  Case R.L., a 45-year-old man, is WBC Differentials 1. Neutrophils-76% hospitalized with a sustained 2. Bands- 13% high fever of 39.4 C, SOB. o 3. Lymphocytes- 10% His cough is productive of rusty 4. Monocytes- 0 sputum, and he appears to be in 5. Eosinophils- 1% acute distress. 6. Basophils- 0 The results of the CBC and On the basis of this laboratory leukocyte differential are as report and other findings, a follows: diagnosis of pneumococcal 1. Total WBC count- pneumonia is suspected. 18,000/µL How R.L.’s laboratory report consistent with bacterial infection? 16  HEMATOLOGY Hematology involves the diagnosis and treatment of diseases of the blood and includes the examination of peripheral blood and the blood precursor cells found in the bone marrow. There are several different hematologic cell types that originate from the hematopoietic stem cell. Each cell line has a defined role and unique contribution to the overall homeostatic process, and may be found in the bone marrow, lymph system, or blood. Typically, routine clinical laboratory testing involves measuring concentrations of mature myeloid cells found in the blood. 17 Complete blood count (CBC) CBC is one of the most An abbreviated method commonly ordered clinical of noting hematologic laboratory tests. parameters in clinical A CBC measures the red blood practice is noted in the cells (RBCs), hemoglobin (Hgb), following figure. hematocrit (Hct), mean cell volume (MCV), mean cell Hgb concentration (MCHC), and total white blood cells (WBCs). Depending on the laboratory, CBC may also include platelets, reticulocytes, or leukocyte differential. 18 White Blood Cells (4–11 × 103/μL) 19 The neutrophil (40–70% of WBC) Segmented neutrophil Life span of about 10 days Moves from bone marrow to blood to tissues Mature more quickly under stressful conditions Granulocytes Primary defense against bacterial infection  Locate, ingest, and kill bacteria and other foreign invaders 20 The neutrophil: neutrophilia  Increase in neutrophil count 1. Pathologic 3. Increased Production of Bacterial infection WBCs Certain viruses and fungi 4. Physiologic Inflammatory responses to tissue  Pseudo-neutrophilia shift of death cells  Catecholamine  Burns ® Acute stress  Snake bites 5. Other inflammatory 2. Drugs responses Steroids  Neoplastic growth Lithium-increase marrow input  Metabolic disorders 21  The neutrophil: neutropenia 1. Decreased Production 3. Pseudo-neutropenia of WBCs Viral infections Bone marrow diseases Hypothermia-marigination Malignancies that affect the bone marrow 2. Increased Neutrophil Destruction Overwhelming infection Certain bacteria Immune reactions 22  Agranulocytosis & Absolute Neutrophil Count Degree of Neutropenia: Infection Risk ANC ANC6.5% A Random blood sugar> 200 mg/dL Blood glucose Cause: