Exam Simulator: Laboratory Operations

The quality of a test to show a positive result in the presence of the disease it was designed to detect is known as: The correct answer is highlighted below specificity sensitivity precision Feedback Sensitivity is the degree to which a laboratory test can correctly identify the presence of a disease in a person who actually has it. The accuracy of a test is its ability to discriminate between the positives and the negatives. Two parameters of test accuracy are specificity and sensitivity. .A test with high sensitivity accurately identifies the presence of disease; it has few false-negatives. A test with high specificity accurately detects the absence of disease; it has few false-positives

sensitivity

The direct relationship between the concentration of a substance and its absorbance is referred to as: The correct answer is highlighted below Beer's law Impedance principle Ohm's law Absorbance principle Feedback The older term optical density (OD) is sometimes used in place of absorbance.

Beer's law

Poor sample application technique during the serum protein electrophoresis procedure can result in wick flow in the separated bands upon analysis. The correct answer is highlighted below True False Feedback Wick flow is caused by excess heat during electrophoresis and can cause distorted bands. Poor sample application can tear the gel and also cause distorted bands.

False

Which one of the following statements regarding factors that affect the mobility or rate of migration in electrophoresis is correct? The correct answer is highlighted below The greater the net charge, the slower the mobility Increasing the pore size in a gel medium slows the rate of migration Increasing the ionic strength of the buffer increases the rate of migration Increasing the heat increases the mobility of the solutes Feedback Increasing the heat increases the mobility of the solutes. This statement is the only one of the four choices that is correct. The greater the net charge of a molecule, the more quickly this molecule will migrate in an electric field. Increasing the pore size in a gel medium speeds up the migration. Increasing the ionic strength of the buffer decreases the rate of migration.

Increasing the heat increases the mobility of the solutes

Mary, Jane, and Pam work in the specimen processing area. Mary sits at the computer station and logs in specimens. Jane's task is to centrifuge and aliquot samples to prepare them for testing. Pam delivers specimens to the testing department. Mary is having frequent mild pain in her neck, shoulders, and wrists. What ergonomic corrective action could be taken to help Mary? The correct answers are highlighted below Mary could stand instead of sit at the computer workstation so that she is looking downward at the computer screen. Mary should take frequent stretch breaks. Mary, Jane, and Pam could alternate or share tasks. Mary should go the the doctor immediately. Feedback Good ergonomic practice may have prevented Mary's problem. Quick recognition of symptoms and corrective action may resolve the symptoms before any serious injury requiring medical treatment. Taking frequent stretch breaks will help to prevent injury. Sharing ergonomically challenging tasks can also prevent injury. Standing and looking downward at the computer screen would probably cause even more problems for Mary as this would be an awkward position.

Mary should take frequent stretch breaks. Mary, Jane, and Pam could alternate or share tasks.

Fluorometers are designed so that the path of the excitation light is at a right angle to the path of the emitted light. What is the purpose of this design? The correct answer is highlighted below Prevent loss of emitted light Prevent loss of the excitation light Focus emitted and excitation light upon the detector Prevent excitation light from reaching the detector Feedback The angle is set at 90 degrees in fluorometers in order to only detect the emitted light from the sample substance after it has been excited with a light beam. This helps to avoid measuring the ultraviolet light emitted from the light beam itself.

Prevent excitation light from reaching the detector

Which of the following BEST describes the relation of nephelometry to turbidimetry? The correct answer is highlighted below nephelometry measures the amount of light absorbed by particles in solution, and turbidimetry measures the amount of light transmitted through a solution nephelometry directly measures the amount of light scattered by particles in solution, and turbidimetry measures the decrease in incident-light intensity nephelometry measures the amount of light emitted by particles in solution, and turbidimetry measures the amount of light reflected by particles in solution nephelometry measures the amount of light absorbed, and Turbidimetry measures the amount of light scattered Feedback The best description of nephelometry to turbidimetry is: nephlometry directly measures the amount of light scattered by particles in solution, and turbidimetry measures the decrease in incident-light intensity. In other words, nephelometry refers to the way a nephelometer measures how much light is scattered by suspended particles in the water. The greater the scattering, the higher the turbidity.

nephelometry directly measures the amount of light scattered by particles in solution, and turbidimetry measures the decrease in incident-light intensity