Laboratory Methods Flashcards
What are the different types of specimens that can be collected for laboratory testing?
Blood Body fluid Urine Microscopic Stool
What are the different types of medical labs?
Hospital lab
Reference lab = sample gets sent outside of place it is taken
STAT lab = more expensive
Point of Care Testing = bedside
What is lab standardization?
Provides accurate and reproducible results
Ensures credible and comparable data across laboratories
What organization is in charge of lab standardization?
National Accrediting Agency for Clinical Lab Sciences (NAACLS)
What is considered CLinical Pathology?
Hematology Chemistry Immunology Serology Immunohematology Microbiology Support Services
What is considered Anatomic Pathology?
Histology
Cytology
Autopsy
Who sets the regulations for medical labs?
Center for Medicare and Medicaid Services (CMS)
These people aren’t medical workers
Who do laboratories work under for regulations?
Clinical Laboratory Improvement Act (CLIA)
What do we currently use to code and classify disease?
ICD-10
What are the two main purposes of HIPAA?
1) Provide continuous health insurance coverage for workers who lose or change their job
2) Reduce administrative burdens/cost of healthcare by standardizing the electronic transmission of administrative and financial transactions = this is where the privacy piece comes in
What is lab quality control?
Gives confidence that results are accurate and Reliable
What does internal lab control evaluate?
Test is working as it should
Enough sample is added
Sample is moving correctly
Electronic functions of instrument working correctly
What does external lab control evaluate?
Entire testing process is performed correctly
Control results are in expected ranges or values as found in manufacturer’s instructions
What is the reference range of a test?
Upper and lower limits generally given as range in healthy people
Normal values vary from person to person
What are therapeutic ranges for lab tests?
Upper and lower limits to measure medication efficacy
MIC
What is Diagnostic cutoff or threshold?
Presence of disease associated with value above a certain threshold
A compromise between sensitivity and specificity
It wants to minimize false negatives and false positives
What is Sensitivity?
Capacity to identify all individuals with disease
What is specificity?
Statistical term indicating effectiveness of test to correctly identify those without disease
What is a positive predicative value?
Likelihood that positive test identifies with disease
What is the negative predictive value?
Likelihood that negative test results identifies someone without disease
What test is an example where the threshold is selected to maximize sensitivity?
HIV screening
What is accuracy?
The ability of a test to actually measure what it claims to measure
Proportion of all test results (both positive and negative) that are correct
What is precision?
Ability of a test to reprocess the same results when reacted on the same patient or sample
What is the pretext probability effect?
Probability you have disease
What are the indications for ordering a lab test?
1) Screening
2) Establish diagnosis
3) Monitor disease
4) Monitor Therapy or medical management of disease
5) Testing related to specific event like a needle stick of sexual assault
What is the process for lab testing?
1) Order test
2) Patient prep for testing
3) Collect sample
4) Transport sample to lab
5) Lab receives sample
6) Lab prepares sample for testing
7) Lab reports results
What are preanalytical values for ordering lab studies?
1) Patient Age
2) Patient Gender
3) Body Mass
4) Preparation of the patient for testing
5) Differences in results with sample type
What are the standard precautions for lab studies?
Sharps Box
Gloves
Eyewear
What are blood studies ordered for?
1) Assess quantities of RBCs and WBCs
2) Levels of enzymes, lipids, clotting factors, and hormones
3) To establish a diagnosis = Elevate BUN and creatinine levels indicate renal failure
4) Rule out clinical problem = Normal K level rules out hyperkalemia
5) Monitor Therapy = PTT values to regulate heparin therapy
6) Establish prognosis = Declining CD4 counts reflect a poor clinical prognosis for the AIDS patient
7) Screen for disease = PSA levels to detect prostate cancer
8) Determine effective drug dosage and to prevent toxicity = peak and trough levels
What is the primary type of blood collected for blood studies and where is it collected from?
Venous blood
From antecubital fossa of the arm where basilic, cephalon, and median cubical superficial veins can be found
If you can’t use the upper extremities to obtain a blood sample, where is the next best place to obtain a venous blood sample from?
Femoral V.
What type of blood study is the first sample to be drawn?
Blood Cultures
What is serum?
Lacks clotting factor
Clotted blood sample
Clear
What is plasma?
Clotting factors present
Anticoagulated blood sample
Slightly more cloudy
What is the order of recommended blood draw?
1) Blood Cultures tubes
2) Nonadditive tubes
3) Coagulation tubes
4) Heparin tubes
5) EDTA-K3 tubes
6) Oxalate-fluoride tubes
What is arterial blood used to measure?
Oxygen
PH
CO2
What arteries are most often used for arterial blood gases?
Radial and Brachial arteries
What is the Allen Test?
Used to assess arterial blood flow to hand and determine potency of radial and ulnar aa.
When is the Allen test performed?
Prior to radial cannulation as placement may results in thrombosis
Used to reduce the ischemia to the hand
What does a positive Allen test reveal?
Patient does not have a dual blood supply to the hand
What type of body fluids can be obtained for lab study?
Sputum CSF Peritoneal Fluid Pleural fluid Semen
What types of swabs can be performed for lab studies?
Wound
Throat and ENT
Genital
Axilla or groin
What are transudate effusions caused by?
Venous Engorgement
Hypoproteinemia
Fluid Overload
What are exudate effusions caused by?
Inflammatory
Infectious
Neoplastic diseases
What does a lumbar puncture sample?
CSF
What does an arthrocentesis sample?
Joint fluid
What does a pericardiocentesis sample?
Heart
What does an amniocentesis sample?
uterus
Why is a urine sample one of the most performed bodily fluid samples?
1) Can diagnose renal or urinary tract disease
2) Can monitor renal or urinary tract disease and treatment of it
3) Can detect metabolic or systemic diseases not directly related to the kidneys
4) Identification of UTI
5) 24 hour urine collection to reflect homeostasis and disease
6) Results of blood test may be normal while urinalysis indicates the presence of metabolites
7) Serum product being tested may be affected by renal clearance
What does a first morning urine sample test for?
Proteinuria
What does a random urine sample test for?
Drug testing
What does a timed urine sample test for?
Postprandial glucose
What does a clean catch urine sample test for?
Culture
What are microscopic studies used for?
1) To evaluate hematologist disorders = bone marrow biopsy and blood smear
2) To detect sexually transmitted diseases
3) To evaluate dysfunctional uterine bleeding = endometrial biopsy
4) To determine liver pathological conditions = liver biopsy
5) To detect lung cancer = lung biopsy
6) To screen for cancer of the vagina, cervical, and uterus = Papanicolaou test
7) To determine the sensitivity of breast cancer to hormonal therapy = Estrogen and progesterone receptor assays
8) To detect renal disease, such as malignancy, glomerulonephritis, and transplant rejection = renal biopsy
9) To detect TB = TB culture or AFB stain
10) TO evaluate and treat infections = body fluids, wound and soft tissue culture and sensitivity
What are stool tests?
Used to evaluate function and integrity of bowel
Represents waste products of digested food
INcludes bile, mucus, shed epithelial cells, bacteria, and other inorganic salts
What is a stool test performed for?
Intestinal bleeding Infections INfestations Inflammation Malabsorption Diarrhea
How do you obtain a stool sample?
Explain method in a matter of fact way
Don’t mix toilet paper or urine with specimen
If female menstruating, blood may contaminate specimen
Ask patient to defecate in designated container then place small amount in sterile collection container
What is endoscopy?
General term referring to inspection of internal body organs and cavities with an endoscope
Named for the organ or body area to be visualized and/or treated
What does an endoscopy permit?
Biopsy of suspicious tissue
Removal of polyps
Injection of variceal blood vessels
Performance of many surgical procedures
What does arthroscopy inspect?
Joints
What does Bronchoscopy inspect?
Larynx
Trachea
Bronchi
Alveoli
What does a colonoscopy inspect?
Rectum and COlon
What does a Colposcopy inspect?
Vagina and cervix
What does a cytoscopy inspect?
Urethra
Bladder
Ureters
Prostate
Why would a lab specimen be rejected?
Improperly labeled Improper storage Wrong tube/sample Insufficient sample Hemolysis Clotted
What errors can occur in lab performance?
1) Pre-analytical phase errors
2) Analytical phase errors
3) Post-analytical errors
What are pre-analytical errors that can occur in lab performance?
Time from patient prep, through sample collection, until the sample arrive in the lab
When do most erros in lab test performance usually occur?
In the pre-analytical phase
What are analytical errors?
Time that sample is being analyzed in the lab
Errors can occur during this, but much less common now because of automation of many lab instruments
What is post-analytical phase errors?
Begins when result is generated and ends when the results is reported to the physician
Delay in time to enter a completed results into the lab information system
Reporting results for wrong patient
What is latex agglutination?
Common lab method in which latex beads are coated with antibody molecules
When mixed with patient’s specimen containing a particular antigen, agglutination with be visibly abvious
What does latex agglutination identify?
C-reactive protein
What is alternative latex agglutination?
Latex beads are coated with specific antigen
In presence of antibodies in patient’s specimen to that specific antigen on the latex particles, visible agglutination occurs
What tests utilize alternative latex agglutination?
Pregnancy testing
Rubella testing
What is hemagglutination?
Used to identify antibodies to antigens on the cell surface of RBCs
RBC agglutination would be visible
What is hemagglutination used for?
Blood typing for transfusions
What is an alternative hemagglutination method?
Different antigens can be bound to RBC surface
When added to the patient’s specimen, specific antibodies can be identified by RBC agglutination
What is electrophoresis?
Analytic lab method where electrical charge is applied to medium on which patient’s specimen has been placed
Migration of charged molecules in specimen can be separated in an electrical field
Proteins can then be identified based on their rate of migration
What is an immunoassay?
Biochemical test that measures presence or concentration of a molecule in a solution using an antibody or immunoglobulin
Relies on antibody to recogniZe and bind specific macromolecule (antigen)
What is the analyte in immunoassay?
Macromolecule detected by the immunoassay
What is the epitope in immunoassay?
Site on the molecule/antigen that the antibody binds
What are the different types of Immunoassays?
Enzymes (ELISA) Radioactive Isotopes (RIA) DNA receptors Fluorogenic reporters Electrochemiluminescent tags Labeless immunoassay
What is a Direct ELISA?
Antibody is absorbed onto the well and sensitized the plate
Test antigen is added; if complementary, antigen binds to the antibody
Enzyme linked antibody specific for test antigen then binds to antigen, forming a double antibody sandwich
Enzyme’s substrate is added and reaction produces a visible color change that is measured spectrophotometrically
What is Indirect ELISA?
Antigen is absorbed onto the well and sensitizes the plate
Test antiserum is added; if antibody is complementary, it binds to the antigen
Enzyme linked anti-gamma globulin (anti-antibody) binds to bound antibody
Enzymes substrate is added and reaction produces a visible color change that is measures spectrophotometrically
What tests use ELISA testing?
Pregnancy testing
Monoclonal Antibody screening
Viral testing (HIV, West NIle)
What is direct Fluorescent antibody?
Antigen is fixed to slide and fluorescence in labeled antibody is attached to it
What is indirect Fluorescent antibody test?
Antigen is fixed to slide and antibody is attached to it and also fixed to slide
Fluorescein labeled antimmunoglobulin then attaches and forms an antigen-antibody complex
What is flow cytometry used for?
Identify cell types
Assesses cell surface markers
What is the goal of a western blot test?
To identify antibodies in patient serum directed at specific proteins
