Use of Laboratory and Collection of Specimens Flashcards
What are the reasons we use detection of infectious agents
guideline for treatment
information for individual cases
collated information for general (publications)
Why is epidemiology important for clinical information
track resistant isolates (e.g., MRSA)
follow trends in development of resistance
detect or confirm outbreaks related to infectious agents
support control efforts, public health support
How do you make the best use of the lab
lab realists correspond to the initial clinical question
decrease frustration - for patients and health care workers (eg., making sure things are properly labeled)
Most cost effective use of lab resources
Speediest results by eliminating delays
What are advantages of being a Smart laboratory user
providing information, to make specialized testing to access unusual circumstances ex. if someone has travelled
avoidance of liability of mislabeled specimens, or loss of specimens
What are the general principles of specimen collection
send as good quality specimens as possible, avoiding contamination with normal flora as much as possible
make sure both specimen and requisition are labled with patients name, date of birth, and health card number, specimen type, etc.
Put relevant clinical information on the requisition
How do you generate the best results and maximize sample quality
use the appropriate transport media to keep the pathogen alive
get specimens to the laboratory rapidly
when in doubt - ask the laboratory (especially if a request is unusual or needs additional testing, or results are unclear, etc.)
when problems arise, work with laboratory staff to fix them
Why is stool weird to transport
in stool specimens they begin to turn acidic because the organism is continuing to metabolize and the number of pathogens you are looking for begin to die off due to acidity
What are general considerations that need to be considered in specimen collection
whether the specimen will provide useful information
Choice of the type of specimen
( sometimes when a patient is very ill you might want a more invasive specimen because that’s going to give you an answer the quickest. Need to balance invasiveness with the info its gunna tell you)
Instructions for collection by patient (tell and physical instructions)
Need for transport media
Time taken for the specimen to get to the laboratory
Quality of specimen (ex. false positive or negative )
How to intreat the results (predictive values)
If a false positive the ___ is low
specificity
If its a false negative the ___ is low
sensitivity
What are the different specimen collections for urinary tract
mid stream urine
in-out catheter urine
indwelling catheter urine
What are the patient instructions for midstream urine
decrease skin contamination by parting labia, retracting foreskin
Cleaning the urethral opening is no longer recommended. first bit of the stream washes out whatever organisms are sitting around the uretha
After passing a few militias collect the specimen in a clean sterile container
How is urine specimens transported
transport medium is not requires if urine is transported to the lab within 2 hours or refrigerated t 4C and delivered within 24 hours
Preservatives/transport medium can be used if delivery to a lab is likely to be delayed or transport is prolonged but usually not because the cost is a lot
label the container with the patients name and another identifier and specimen type
What do you not collect urine from
bedpans, urinals or catheter bags
How to collect urine from in/out catheters
use aseptic technique (dont want to introduce new organisms) to the catheter
discard the first few ml of urine that pass
collect the specimen and send
how to collect urine from indwelling catheters
collect the specimen using a needle and syringe after cleaning the collection site with alcohol, and send
they have more organisms and are more difficult to interpret
What specimen types are there for respiratory tract specimens
sputum (cough it up)
induced sputum (if you have a dry cough and cant cough anything up)
tracheal aspirate (sedated)
how do you collect a respiratory tract specimen if its suspected that a patient has TB
use precautions to prevent spreading infection
don’t have them cough in your face, get them to do it another room
What are the patient instructions for sputum collection
decrease contamination by saliva by removing dentures, clean teeth
acid collecting post nasal discharge
deep cough from the chest into the bucket
how are teeth cleaned in a sputum collection
Gargling and using mouth with sterile water
no toothpaste because the residue may have fluoride in it which is antibacterial
not tap water, may be contained with legionella or pseudomonas
How is sputum collection transported
in a dry sterile container
transport to the laboratory as soon as possible but at least within 24 hours
refrigerate at 4C if there is a delay in delivery
When might a sputum collection not be cultured
they may not culture it if there is a degree of contamination with saliva by identification of squamous
When is induced sputum collection used
induction of sputum using aline aerosols can be useful if patient cannot produce sputum
sputum produced after bronchoscopy is a good specimen also
need to label because it will look like saliva
when is tracheal aspirate collection used
useful in incubated patients, may not be perfect as material may be pooled in the back
specimen collection traps are prone to leaking during transport too (30% of time)
How do you collect enteric specimens
stool
What are the patient instructions for stool collection
pass stool on clean sry surface, eg., paper or plastic
if liquid into a clean container
place an almond size (with shell) sized portion in the specimen container
How is stool transported
transport to lab as soon as possible or refrigerate at 4C (no more than 24 hours)
send stool rather than rectal swabs if possible
What are the 3 types of stool transport media
- for culture use enteric (cary Blair) transport medium
- for parasites use SAF (formalin, saves and preserves) parasite preservative
- For cytotoxicity and virology testing (ex. C. diff) use dry sterile container because nucleic acid identification
What are swabs used for
throat, wound, urethra
What are swabs not used for
abscesses (want a container of puss as its a good transport medium),
fluids,
TB culture (swabs don’t work good, micro bacteria gets in the swab)
What are the instructions for using swabs
use a swab only if there is insufficient quantity to collect in a syringe and send in a dry sterile container. some material will be absorbed by the swab
collect purulent material
avoid contamination with surrounding normal flora on skin
How do you transport swabs
use an appropriate tranport medium to increase organism survival or for specific organism (eg., Neisseria gonorrhoeae culture, viruses, clamydia)
some instruments use specific swabs (eg., chlamydia and n gonorrhoeae) have specific systems related to their pHs that work well
avoid dry swabs for sending specimens as the organisms will die off
anaerobic swabs are 20x the cost of aerobic swabs and so should be used judiciously (e.g., on deep infected wounds but not on mucous membranes)
When to use dry swabs
for making slides
when are biopsies or sterile fluids used
tissue
pleural fluid
pericardial fluid
CSF
vitreous fluid
What is the instructions for collection of biopsies and sterile fluids
collect in a dry sterile container and send to the lab without delay
labelling must be complete and correct
it is not necessary to add sterile water to biopsies unless they are very small and in danger of drying out ( add a few drops to maintain humidity)
microbiology specimens should never be put in formalin (it kills all the bacteria)
How long does it take for microscopy realists to be avaliable
1-2 hours for stat samples
How long do culture take for results
may take from overnight to several weeks for some organisms. most are available within 3-5 days
TB takes a week at the fastest
fungi takes awhile too
How long does rapid testing (antigen detection take for results)
may be available on the same day
