chem lec test 1

what are the two types of pipette designs

TC: to contain not guaranteed to dispense but guaranteed to hold precise amount of specimen

TD; to deliver will deliver exact what is drawn

what are the two types of drainage that a pipette can have

blow out: usually on to deliver -usually TD (2 etched lines or one continuous line)

And self draining

what are the two types of pipettes

measuring or graduated (use the pipette that is the closest to the volume you want) and transfer holds certain amount of fluid

what is the Mohr pipetts

TD, measuring graduated, self draining with graduations ending before the tip

what is the serological pipete

measuring pipette graduation marks continuous to the tip always read at the mininscus

what are pasteur pipetes

volumetric pipet made of glass or plastic, not very accurate

automatic multiple volume pipet (micro)

volumetric pipet with disposable tips holds 1 mL or less

what is an ostwald folin tip

volumetric pipet used for viscous body fluids (longer width)

what are biurets used for

for titrations

how should a specimen always be collected

pipet upright and immersed about 1cm from the top of specimen (only tip in)

what is a volumetric pipet

high deg of accuracy used when running controls, settings, calibration, and rehydration

describe any specifics on flasks, beakers, cylinders, and flasks

griffin beaker, Erlenmeyer flask, and graduated cylinder; can measure, but can be inaccurate -use the cylinder closest to vol wanted for most accuracy; volumetric flasks have one measurement, but instead are very accurate

describe desiccators and desiccants and why we have them

desiccants: drying (pull moisture out) for preservation usually packets of silica dell dessicator+dessicant needs to be rehydrated (glass jar and beads) why is it used? so reagents dont loose their reactivity

what is the right to know act

set by OSHA for hazard communication, includes SDS and warning labels for every chemical (seen on FRANC0

what is the chemical hygine plan

written plan for chemists on what PEE and hoods to use, how to train and communicate with each other, and the need for a safety officer

explain the diamond hazard rating rules for chemicals

by the NFPA found on all chemicals; Blue: health hazard White: specific hazard Red: fire hazard Yellow: instability graded from 0-4 4=most hazardous 0=least hazardous)

what are the categories of chemicals

corrosive, toxic, carcinogens, flammable, reactive

describe corrosive

visibly causes destruction to human tissue with contact with contact

describe toxic

ingestion/inhalation/direct contact (absorbed) with acute or chronic effects- doesn't react directly with tissue but instead interferes with metabolic pathways

describe carcinogens

any chemical known/able to cause cancer in humans/anicmals

describe flammability v combustability

flammable: they can cause fire/ explosion defined by their flashpoint (below 37.8 deg C combustible: flashpoint above 37.8 deg C

how must flammable items be stored

in explosion or flammable proof cabinets, dont store more than 1 pint of substance, store at eyelevel or below (5 ft), never store near electrical current, never pour down the drain

describe a reactive chemical

substances that under the right conditions can spontaneously explode or ignite (many are oxidizers)

where should you never store a chemical

in a fume hood (and it ALWAYS must have proper labeling)

what does NFPA stand for

national fire protective association

list some rules that must be followed regarding chemical storage

oxidizers (reactive chemicals) stored away from others inorganics stored away from organics; store in dry place away from heat

describe gas cylinders and how should they be stored

compressed gas (ie O2/CO20 used for things like incubators, under tremendous amnt of pressure, can be projectile if broken, store it upright and chained to the wall (keep it in its own storage room), open valve slowly and transport with protective caps on

how is chemical waste supposed to be disposed

by professionals who are registered with EPA, have special training

what is medical waste

in 1998 OSHA said any waste that can transmit infectious diseases including sharps

what are approved methods of disposing of medical waste

all in biohaz bag/ leakproof; can be incinerated, steam sterilized (autoclave), bury it, thermally inactivate, chemically disinfected

list all the different classifications of fires and how they are handled

A: wood cloth paper handled with ABC or water

B: grease, gas, paint, oil handled with ABC (foam/chms)

C: electrical equipment handled with ABC (chem powder)

D: combustible material (mercery) handled by professional with special extinguisher

K: kitchen like oils handled with wet chemicals

descrive PASS

pull pin, aim, squeeze, sweep

what does a globally harmonized system mean

universal set of symbols used to indicate different types of hazards

what does CLSI stand for and what is it for

clinical laboratory standards institute for the classification of water

whats the difference between DI and distilled water?

distilled: h2O purified via distillation, removed organic components DI: distilled but included removing ions

what are the tiers of reagent grade water

3- least pure (cleaning glass wear)

2- used for most analytical procedures (rehydrating regents/cntrls/buffers can expire and cant be stored for long time

1- most pure used for minimal interference for rehydrating controls for trace metal analysis can be used for calibrators, expire after 24 hrs after opening

what are the rules of centrifusion

1- balance 2- never manually stop 3- dont centrifuge till a specimen is full clotted (fibrin strands can throw off analytes)

what are the different types of centrifuges

fixed angle rotator, vert. tube rotator, swinging bucket rotator (most common)

the difference between accuracy and precision and why are they done

accuracy: how close is target value precision: hitting the same value over and over; done to ensure reliability

describe preanalytical, analytical, and postanalytical errors

pre: anything happening before tube is run (most likely to happen) analytical: happens while specimens are being run post: reporting of results improperly

define population

all possible values for a particular characteristic

define sample

part of defined population (representitive)

what is standard deviation used for

measures degree of precision and determines distribution of random error

what are the measruements of central density

mean, median, mode

what are the measurements of variation

range and standard deviation (helps determine 'normal ranges')

what is the gaussian distribution of variables

pretty much just a bell shaped curve

what is coefficient of variation used for

measure precision (as a percent, must be under 5%)

what is random error

reflection of precision (dont want to duplicate) caused by tech themselves (extreme results) you must figure out what went wrong, multiple errors lead to lowering of the mean

what is systematic errors

reflects accuracy of methodology tends to shift mean to one side (L or R) can be from a system error and take a while to detect

what is a system error

error in instrumentation such as faulty equipment or reagent (control old or light intensity has decreased)

define a shift

abrupt change in mean that remains constant

define trend/drift

steady incr or decr away from the mean

how to define a shift

look at past 6 days worth of variables (usually caused by something new introduced in the system) note when it happened and why it happened

how do you define a trend/drift

trends are often caused by reagent or lamps getting old again look at 6 days of variables you have to note and explain why its happening

how to fix trend

restart recalibrate do preventative maintainance

how is reference range found

found by finding mean and standard deviation

what to do if reference range is published and when your range doesnt match up

(with preset values) can adopt these values but still want to establish your own criteria by taking 20 people and comparing it to published media; if 3+ people fall out of 2 SD, then do 20 more people if this happens again 120 healthy people are needed

how to find a reference range for a new analyte

this is no pre publish guide need 120 people to sample for a normal reference range, find the mean standard deviation of them and publish results (with enough it will be prepublished by the CDC)

what is the analytical range

range of conc, of analyte in a sample over which the test method used is applicable without modification (range that the test can detect: what is the lowest and highest amnt of analytle machine can detect without dilution); you want a LARGE range

what is another word for analytical range

linearity

what is a delta check

comparison of results from one person with result from the same person on a previous sample (threshold usually 5-10%) this can warn us if its a wrong patient or major change in the patient

what do you do if you get flagged with a delta check

check patient ID, check of hemolysis and lipemia, check for diurnal variation of the analyte, check if it was spun or sat in the light

define diurnal variation

diff in analytes throughout the day (common: iron and cortisol)

define standard sample

a stable non water absorbing substance that can be dried without changing composition

what is a calibrator

the standard material of a known composion and a high degree of purity

when do you calibrate machines

when a shift is seen or when the power goes out

define a control

used to monitor performance of an assay by setting machines (using a calibrator) used to ensure accurate results of tests; it is from a human and is tested for Hep B/C and HIV

define lypholized

freeze dried control (pellet) need to rehydrate it (package will include direction s and how long it should sit for)

list the pros and cons of liquid and lyophilized controls

liquid: can use it immediately lyophilized: has a longer shelf life

what is a carry over study

uses low and high balues to study patient reults on an automated analizer commonly used with DOA; L1,L2,H1,H2,L3 (one low and one high control) less than 10% is acceptable

what are method validation studies

done to validate results coming from two different methods (like new machine or test kit)

steps preforming a method validation study

1) research new method 2) do study (based on CLIA according to OSHA) need at least 40 different samples, run patients in duplicate (both old and new method is run twice) if results are within 5% of each other than its accepted; if 1-2 fall out of 5% than reject and get new patients, if 3 are different then you have to get another different 40 patients

what is CLIA

clinical laboratory improvement amendments

what is bias

how different is one set of results from another

how is bias found

mean of old method-mean of new method ideally you want it to be 0 but if its within 5% then its acceptable; usually is plotted on linear regression analysis graph (new method=x and old method=y) want to see a straight line on graph

what is positive bias

mean is slightly higher in new mehtod than old method

what is negative bias

mean is slightly higher in old method than new method

what is the gold standard of testing

method used for multiple years to get accurate results

how is sensitivity and specificity usually testing (ie who)

first on healthy patients then add some unhealthy then ones that can give both high and low results

Define sensitivity

number of true positives in a specimen; test with detect what you want no matter how small the concentration of analyte or organism is

define specificity

measures true neg ; how specific can your test method be in only picking what you want to detect

define true positives

number of gold standard pos

false negatives

diff btwn gold standard positives and new method positives

define true negatives

number of gold standard negatives

define false positives

number of new method positives minus gold standard postives

define prevalance

frequency- helps to decide whether or not a result is believable

what does it mean when you are prevalence positive

you are x% positive someone has said disease

what does it mean when you are prevalance negative

you are x% certain that the test (neg value) is correct

what does internal QC do

checks accuracy and reproducibility of a test result by controls (preformed in house, feedback is quick and used for immediate disicsions)

why must a lab do external quality assesments/proficiancy tests

to get reimbursed by insurance (any lab doing moderate/complex tests- such as gram staining 'needs' to apply)

what does CAP stand for

college of american patholigists

when are CAP tests done and what happens when you pass/fail

typically done every quarter if you fail then you have to figure out why and rerun specimen then explain what happened if you fail multiple times in a row the lab wont be allowed to run the test until they are proficient in it

what are the rules to follow when testing a CAP specimen

test like a normal specimen, dont consult with another lab, specimen never leaves the lab

what is a competency assessment

(part of QC) done throughout the year with CLIA it is done when tech is hired, 6mo after employment, 1 yr after initial employment, and every year after that it is required to be regulated (no favoritism)