Derm Flashcards
Why do we use medical diagnostics?
Use as confirmation, not the end all be all. 6 billion used annually.
What are the modalities for medical diagnostics?
Imaging, Direct visualization, measurement, cellular analysis, chemical analysis, molecular analysis, microbiology.
What are the purposes for diagnostic tests?
Screening, diagnosis, staging/prognosis, monitor disease progression, drug selection, treatment monitoring. Grade an injury, localization of biopsy, establish diagnosis or narrow a differential.
What are the types of imaging?
Radiography (X-ray technology), Computed Tomography (CT), Fluoroscopy, Ultrasound (US), MRI, Nuclear Medicine Imaging, Positron emission test (PET).
What is Radiography?
X-ray technology, traditional x-rays (‘plain films’) and anything -graphy/gram.
What is Computed Tomography (CT)?
Lots of x-rays from many different angles and computer creates composite.
What is Fluoroscopy?
Lots of x-rays from the same angle, computer creates video.
What is MRI?
Soft tissues better seen with ligaments and tendons.
What is Nuclear Medicine Imaging?
Uses radioactive tracer; darker areas indicate hypermetabolism and are indicative of cancer.
What is a Positron emission test (PET)?
Radioactive tracer uptake scan.
What is Direct visualization?
Scopy indicates the insertion of a camera into a space.
What is Measurement of function?
Recording of organ activity, e.g., ECG/EKG, EEG, PFTs.
What are the broad categories of lab methods?
Microbiology, chemical analysis, cellular analysis/Hematology, Histology/tissue analysis, Molecular/Genetic analysis, microscopy.
Define Microbiology Diagnostics.
Staining, culture and identification, antimicrobial sensitivity testing.
What is Microbiology staining?
Chemical is added to a sample that provides color to help differentiate microorganisms.
What is a Basic stain?
Stains everything.
What is a Gram stain?
Most bacteria, differentiates into gram + and gram -.
What is India Ink?
Used for cryptococcus, visualize cell wall of bacteria with capsule.
What is Acid Fast staining?
Used for mycobacteria (TB).
Define Microbiology culture and ID.
Agar plates and microtiter plates.
Define Chemistry Diagnostics.
Many chemical tests use color change to detect the chemical/molecule.
What types of chemistry diagnostics are there?
Electrode management, chromatography/spectrometry, enzyme assays, immunoassays, Gel Electrophoresis.
What is electrode measurement?
Used to measure small changed molecules, e.g., Na, Cl, K, Ca.
What is chromatography/spectrometry?
Molecules are separated by chromatography then analyzed by spectrometry.
What is an enzyme assay?
Procedure: A substrate is added to the well. A sample from a patient is added to the well. If the sample contains the enzyme, there will be a color change.
Define Immunoassays.
Detection of a specific antigen or antibody of interest using antibodies for detection.
What are methods of Immunoassays?
Agglutination/precipitation, ELISA.
What is gel electrophoresis?
Separates based on size. Gel provides barrier that selects for size.
What is flow cytometry?
Cells passed single file past a detector, can be separated based on size.
What is Histology/Tissue Analysis?
Biopsy of tissue examined under microscopy.
Define Molecular and Genetic Diagnostics.
Detection and/or analysis of DNA/RNA (mRNA).
What is the PCR process?
Genetic material isolated, primers and components added, sample heated to cause separation of strands.
What is nucleic acid amplification?
Simplified PCR process on a smaller scale, mostly used with microorganisms.
What is detection of mutations?
Single mutations: primers with a single mutation are added to the patient’s sample.
What is whole chromosome analysis?
Karyotype: dividing cells-chromosomes separated by size into pairs.
What is microscopy?
Analysis of body fluids under the microscope.
What are some things to consider when ordering tests?
Purpose of the test, timeliness, harm of false results, cost effectiveness, invasiveness, special preparations, follow-up likelihood.
What are some differential diagnoses?
Possible diagnoses that guide your selection of tests.
What are some testing sequencing?
Initial test should be high yield, cost effective, low risk.
What is important to know about patient education?
Provide patient/family info on indications, contradictions, risks, special preparations, when results can be expected.
What is important to know about test performance?
Tests that PAs can perform include lumbar puncture, joint aspiration, wound culture, swab, biopsy, skin scraping, urinalysis.
What do we know about interpretation of tests?
Types of results depend on the type of test; results are compared to a standard for interpretation.
What are some factors that can affect test results?
Age, gender, body mass, fasting vs non-fasting, time of day, temp, timing of collection, interfering factors.
What is important to consider in reporting of results?
HIPAA considerations and critical values.
What are our test characteristics?
An ideal diagnostic test would perfectly identify those who do have a disease vs those who don’t.
What are some important test characteristics?
All diagnostic tests have overlap between values of people with disease vs people without disease.
Define Precision vs Accuracy.
Precision: obtaining results close together; Accuracy: obtaining results close to the true value.
Define Sensitivity vs. Specificity.
Sensitivity: helps rule something out; Specificity: correctly identifies all individuals without the disease.
What are the four outcomes for a diagnostic test?
True positive (TP), False negative (FN), True negative (TN), False positive (FP).
Define Prevalence and Incidence.
Prevalence: number of people with a disease at a specific time; Incidence: number of people with a disease over a given time frame.
Define predictive value.
Likelihood that a test yields a true result.
What is an odds-likelihood ratio?
Likelihood ratio (LR) incorporates sensitivity and specificity into a single measure.
What is an LR?
A number used to assess how much impact a test result has on the patient’s likelihood of having the disease.
What are Derm diagnostics?
Visual exam, skin scraping, biopsy, allergy testing, and specific tests for infections.
What is dermoscopy?
Portable microscopy for evaluating pigmented skin lesions.
Define Diascopy.
Evaluation of a red pigmented lesion for blanchability.
What is KOH prep?
Can be used with skin scrapings to visualize pathogens.
What is a biopsy?
Remove intact layers of skin for examination.
What are biopsy indications?
Concerning lesions, bullous disorders, inflammatory disorders, failed treatment.
What are allergy testing methods?
Prick/scratch test, intradermal, patch.
What is serum used for?
Tested for IgE antibodies to specific antigens.
What are some tests for skin infections?
Woods lamp, Tzanck smear.
