Common Diagnostic Methods Flashcards
What does potentiometry measure?
the electrical difference between two electrodes in a cell
what the two electrodes used in an ion-specific electrode?
sensing (contains ion-selective membrane)
reference
how does an ion-specific electrode (ISE) work?
a potential difference develops at the ion selective membrane because of the difference in ion activity between the test solution and the internal electrolyte solution
what can be used to measure sodium, potassium, and chloride?
ISE
Examples of antigens used in immunoassay
Troponin T, marker of cardiomyocyte injury
examples of antibodies used in immunoassay?
Hepatitis B and C, HIV antibodies
how does immunoassay work
it takes advantage of antibody specificity for corresponding antigens
which immunoassay is often used for urine drug screens?
EMIT
enzyme multiplied immunoassay technique
what is the Hook effect?
production of artifactually low results from samples that have extraordinarily high concentrations of antigens, exceeding the upper standard
What is a potential cause of the Hook effect?
saturation of the capture antibody by the vast excess of analyte, preventing the binding of the signal antibody
heterophilic antibody interfence
-antibodies to animals that can interfere with immunoassays
-may arise as a consequence of close contact with animals
-can cause falsely elevated results if the heterophilic antibody bridges the signal and capture antibody
measurement of light
photometry
measurement of light at a specific wavelength
spectrophotometry
measures the reduction in the light transmission caused by particle formation in a solution, and quantifies the residual light transmitted
turbidimetry
the measurement of light scattered by a particulate solution, like a solution containing antigen-antibody complexes
nephelometry
