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Chemistry year 2 > Year one review > Flashcards

Year one review Flashcards

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1
Q

Direct ISE

what
composed of and types
application

A

measures ion concentration directly from sample

Electrodes and membranes

Glass Electrodes- for Na ions
Ion exchange electrodes- K ions

Membrane - selectively permeable
Glass membrane - permeable to Na ions
Polymer membrane- for K only

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2
Q

Clinical application of ISE

A

EMERG OR critical care

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3
Q

indirect ISE

what electrodes
membranes
dis/ad

A

measures ion concentration indirectly by measuring conductivity or total ionic strength first

electrodes - more componenets than direct ise

membranes- measures OVERALL conductivity

advan-less affected by turbidity

disadvan - less precise

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4
Q

HIGH hct means
serum ____ is higher than whole blood

A

less plasma so less CL

serum CL is higher because it is the extracellular fluid compartment where chloride is concentrated

good to know where hct levels are abnormal can affect CL especially if the wrong RI is used

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5
Q

What is Anion gap

A

Anion Gap (mmol/L) = [Sodium] – ([Chloride] + [Bicarb])

identifies electrolytes and acid base disorders (DKA), metabolic acidosis

need to calibrate instrument regularly because K, Na and CO3 need to be measured precisely
-be sure to verify against known standards
-if you track anion gap over time you can ID trends or deviations from expected values which would be an issue with testing or instrumentation

-be sure to participate in proficiency testing

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6
Q

if anion gap falls out of range what does it signal

A

reagent degradation , calibration errors, deviation from procedure

high anion gap - DKA, LA, renal failure due to accumulation of acids or unmeasured anions

normal anion gap MA - diarrhea, loss of CO3 but not increase of other ions

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7
Q

What do you do when reviewing a delta alert

A
  • review results, pt history and sample handling procedures

contamination, incorrect collections, reagent issues,

by looking at delta check patterns labs can identify systemic patterns

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8
Q

calibrators vs standards

A

Calibrators have known concentrations used to adjust and verify the accuracy of an instrument. –helps to establish a relationship between the instrument’s output and the actual analyte concentration
-creates a calibration curve

Standards- have well-established and validated concentrations
or values, used as references for comparison
-used to check the ongoing accuracy
of test results but are not used to adjust the instrument.

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9
Q

Calibration drift

A

gradual deviation from true value

wear and tear, environmental changes, reagent degradation , humidity

helps to calibrate regularly

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10
Q

interpreting calibration curves

A

relationship between calibrator and instrument
-curve should be linear
-slope is the sensitivity of the instrument
-if there is a deviation then recalibrate
-calibration verifies the intrument accuracy to match known RI

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11
Q

QC is

A

monitoring ongoing accuracy and precision

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12
Q

What is osmolal gap

A

difference between measured OSMO and calculated OSM. detects unmeasured osmo active substances in the blood

(2*[sodium]) + [Glucose] + [urea] -used when there are unmeasured substances

used for detecting toxins (alcs) , poisoning, metabolic conditions

increased - presence of unmeasured osmotically active substances - investigate further

normal osmolal gap means you have nothing additional in your system just NA, GLUR, UREA

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13
Q

edta and interferences

A

binds CA to prevent clotting

CA/MG bind EDTA so you cant use edta to measure them

enzyme activities - enzyme assays that need calcium as a cofactor will be affected

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14
Q

Heparin and interferences

A

activates antithrombin III, inhibits thrombin and prevents clot formation

-used for plasma biochem tests like electrolytes and glucose

interference
lithium heparin - can artifically increase lithium and sodium heparin can increase sodium

falsely low calcium - heparin can bind to calcium mostly in calcium tests, causing inaccurate results.

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15
Q

citrate and interferences

A

binds calcium to prevent clotting - forms calcium citrate complexes

-interferences
Ca/Mg: citrate binds CA so it cant be used for tests that need CA or MG testing

Dilution effect- liquid ANTICOAG can dilute the sample and lead to falsely low concentrations

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16
Q

Oxalate/Fluoride and interferences

A

oxalate precipitates Ca and fluoride inhibits glycolysis

-used for glucose and lactate levels

interfernces -
Ca just like EDTA and citrate - affects ca measurement

Enzyme Assay - fluoride inhibits enzyme reactions so that will affect tests that rely on enzymatic methods

17
Q

Colorimeteric testing

A

quantifies analytes based on color changes resulting from chemical reactions with specific reagents, intensity of color is proportional to concentration of analyte

-dilute or treat to remove interfering substances
-measurement with a spectrophotometer at a specific wavelength
-compared against a calibration curve

glucose w/ glucose oxidase
Tp with Biuret method
Bilirubin assay for LFT

susceptible to interference from hemolysis, lipemia, and other sample conditions

18
Q

reflectomertry

A

-measured intensity of light reflected from colored surface to determine concentration on analyte
-sample applied to a test strip with reagents

reflectometer measures intensity of light reflected from colored area of test strip where analyte was placed

POCT with test strips
urine dipstick tests for glucose, protein, ketones

Limitations- dependent on quality of test strips and interference from contaminants

19
Q

refractometry

how is it done and what is it affected by

A

measures refractive index of a sample which changes the concertation of a solute
-used to determine protein concentration in serum and specific gravity of urine

-use a refractometer
-refractive index is read on a calibrated scale which correlates with analyte concentration

-used to measure serum protein
-measure USPG to assess kidney function

-affected by temperature , needs a temp correction

20
Q

Nephelometry

how is it done and what is it affected by

A

-measures light scattered in particles in suspension
-amount of light scattered is directly proportional to concentration of particles good for measuring quantifying proteins or immune complexes

-sample mixed with reagent that forms insoluble particles
-measures intensity of light scattered at a specific angle which is compared to a calibration curve to determine analyte concentration

-used to quantify proteins in serum - IGG, or for immunology
-good for proteins or immunoassay

-affected by high lipid levels or particulates

21
Q

turbidimetry

how is it done and what is it affected by

A

-measures reduction in light transmission due to particles suspended in a liquid different nephelometry by measuring the decrease in light passing through the sample rather than the scattered light.

-analyte + reagent form precipitate or suspension measure decrease of light with turbidimeter and compare the reduction to a calibration curve

good for bacteria concentration in culture or clot formation in COAG

-less sensitive than nephelometry for detecting low concentrations

22
Q

sandwich immunoassay

how is it done and what is it affected by

A

-highly specific to detect AG in sample
-bind an AG to two AB : capture and detection AB = making a sandwich

Capture AB coating - a solid surface (microtiter) coated with AB specific to target AG

-target AG binds to capture AB
- detection AB conjugated to an enzyme or
fluorescent marker is added, binding to another site on the antigen
-substrate for the enzyme is added producing a signal (colorimetric, fluorescent, or luminescent). measure intensity of signal to STANDARD curve

good for detecting hormones (TSH, hCG)
measuring biomarkers (TNIHS)

limitation - needs multiple AB and can be time consuming

23
Q

competitive immunoassay

method
application
ad/dis

A

measure AG concentration by competing with a labeled AG for a limited number of AB binding sites. The signal produced is inversely
proportional to the concentration of the target AG in the sample. Intensity of signal compared with standard curve

Good for measuring small molecules - drugs hormones , detecting AB in autoimmune diseases

DIS- Inverse signal relationship requires careful interpretation.

24
Q

Which quality control measure is most critical in ensuring accurate electrolyte testing
results on an ISE analyzer

A

Monitoring internal quality control results for trends or shifts

25
Q

After a recent calibration, the ISE analyzer reports unusually high sodium levels in all
patient samples. Which of the following is the most likely cause?

A

Incorrect preparation of the calibration solution

Incorrect calibration solution preparation can cause systematic errors across all tests

26
Q

Which of the following would most likely indicate a quality control issue with electrolyte
testing in the analytical phase

A

Sudden shifts in control values without a change in reagents or equipment

Unexpected shifts in QC values suggest an issue with the testing process or equipment, warranting investigation to maintain accurate results

27
Q

a gradual shift suggests?

A

potential maintenance or
calibration issue. Reviewing the logs for missed procedures can help identify if a lack of
proper maintenance is causing the drift

28
Q

External Quality Assurance (EQA)

A

systematic approaches designed to monitor and assess performance of labs and compare them to other labs

Regular Assessment:
Benchmarking:
Feedback and Improvement:
Regulatory Compliance:

29
Q

Regular Assessment:

A

EQA programs are done regularly (quarterly, annually) where labs submit test results for standardized samples to compare with other labs and establish RI

30
Q

Benchmarking:

A

performance metrics- evaluated based on ability to produce results that are in ranges with other labs - identifies areas where they can improve

31
Q

Feedback and Improvement:

A

reports - detailed feedback

CA- labs need to take corrective actions to address issues and improve processes

32
Q

Regulatory Compliance

A

standards- making sure lab standards align with global guidelines

accreditation - needed for certification

33
Q

What is potentiometry

A

Potential develops at measuring (indicator) electrode
-membrane molecules selectively bind measuring IONS and there is a potential measured with voltmeter

-Reference potential compared to potential at measuring electrode: Nernst equation: expresses potential as related to activity of analyte
- Activity of ion is converted to concentration in mmol/L

DIS-protein build-up on electrodes: decreases life span

Chemistry year 2 (12 decks)

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