Urines Flashcards
What tests are done on urine samples
Sedimax analysis for wcc, rcc, epi count
HCG/Pregnancy Test
Listeria rapid antigen test
How does the SediMax work
On board the analyser, urine is mixed until homogenised
0.2ml of the sample is taken up and transferred ino a special disposable cuvette by a pipette
The pipette is then rinsed with instrument feed water (IFW) to avoid cross-contamination
Cuvettes containing sample are then centrifuged at 2000 RPM for 10 seconds which forces all the particles in the urine to sediment onto a single plane on the bottom of the cuvette, this is where the camera focuses on
The built-in camera then takes both bright-field and phase-contrast pictures through a microscope at 10 different points across the specimen
A high-performance image evaluation software then processes all of the images to detect and classify and particles
All the images are then stored on the analysers memory which can hod 10000 records
What is the principle behind the SediMax
A fully automated urine analyser
Uses bright-field and phase-contrast microscopy to visualise and recognise formed elements of urine
What cells can the SediMax identify?
Red Blood Cells (RBC);
White Blood Cells (WBC);
White Blood Cell clumps (WBCc);
Hyaline Casts (HYA);
Pathological Casts (PAT);
Squamous Epithelial Cells (EPI);
Non-Squamous Epithelial Cells (NEC);
Bacteria (BAC); Bacteria Rods(BACr);
Bacteria Cocci(BACc)
Yeast (YEA);
Crystals (CRY):
Calcium-oxalate monohydrate (CaOxm),
Calcium-oxalate dihydrate (CaOxd),
Uric acid (URI),
Triple phosphate (TRI);
Mucus (MUC),
Sperm (SPRM),
Amorphous material (AMO)
How is the SediMax maintained?
Run Milton disinfectant once every day first thing in the morning
QC ran twice a day, once in morning, once in afternoon -> Two controls, a high and a low control
What urines are cultured
Any urines with a white cell count greater than 20
Urines are also cultured upon request or if the patient is immunocompromised i.e. from St. Vincent’s ward etc
What will you have to do if the white cell count is very high on a urine sample?
If WCC is very high you will have to dilute the sample 1 in 10 in saline
You then run the sample as normal but change the dilution factor so that the correct result goes across
If wcc still too high then repeat the dilution to create a 1 in 100 dilution
What is the name of the tubes used on the SediMax?
Sedivette tubes
How much urine is needed for analysis of urine?
At least 2 mls -> if less urine then this than a manual will have to be done using a cell counter
How many pictures does the SediMax take of a sample?
SediMax will take 10 pictures of different areas on the sample
If wccs too high in a certain picture the SediMax will not count this: 9/10 pictures taken
7/10 pictures or less will have to be diluted
Do you culture a urine if the bacterial count or rcc is high?
No -> only if wccs also high
What would a high urine bacteria count without a raised white cell count mean?
Poorly taken sample
Urine is meant to be a midstream urine
Bacteria without wcc = commensal bacteria
Patient could also be immunocompromised
What would a raised red cell count without wcc mean?
Patient could be menstruating
It would be up to the consultant to determine the cause of the raised rbcs, the urine can be cultured if requested
When would you carry out a manual urine
Only done when there is very little sample i.e. less than 2mls
How would you carry out a manual urine?
Carried out using a cell counter
Cell counter composed of six squares broken down into 16 squares
Manually count the ebcs, rbcs and epis in one of the sets of 16 squares
If too many cells in sample you can carry out a dilution just make sure to multiply results up to account for the dilution factor
How did you deal with casts and crystals in urine
There is no quantitative measurement of either
They are detected through microscopy
Detection is qualitative
Detection is not diagnostic, only really informs the consultant on the patient’s diet
Talk about the HCG pregnancy test
One of our urgent tests as the patient is usually due to go for surgery
A negative pregnancy test is required prior to surgery for females
It’s a simple antigen test which only takes 3 minutes
If there is any feint line showing any positivity then a second test should be carried out
If still unsure then ask another scientist
Talk about the legionella or pneumococcal antigen tests
Specific antigen tests done upon request
Pneumococcal antigen test usually done if query pneumoniae -> detects S. pneumo in urine
Legionella antigen test only done for patients in A&E or HDU/CHDU but can be added on by the consultants if required
What agar are positive urines put up on?
Chromagar Orientation Plates
What is the Chromagar Orientation plate?
a non-selective chromogenic culture medium intended for use in the qualitative direct detection, differentiation and presumptive identification of uropathogens to aid in the diagnosis of urine tract infection
What are the most common urinary pathogens?
E. Coli (majority)
Enterobacter (Ents)
Staphylococcus Saprophyticus in young women
What colour will an E. Coli grow on urine chromagar?
E. Coli = pink
What colour will GNBs grow on brilliance chromagar
GNBS = large and blue but some can also be colourless
What colour will your Ents grow on Brilliance chromagar
Ents = bright blue (smaller than GNBS and not as dark)
What colour will S. saprophyticus grow on brilliance?
Light pink -> not as bright as E. Coli
How will Pseudomonas grow on Brilliance
Pseudomonas will have a greeny metallic sheen to the colonies
For how long are the agars incubated?
At least 16 hours
Preferably 16 - 24 hours but GNBs usually grow in a few hours
How do you carry out a colony count for urines
1-9 colonies = <10^4 cfu/ml
10-100 colonies = 10^4-10^5 cfu/ml
>100 colonies = >10^5 cfu/ml
Why do we carry out a colony count for urines?
Less than 5 colonies/scanty growth is rarely every causative of infection
Unless the organism is a query GNB then we don’t pick a scanty growing organism i.e. less than 5 10 colonies
How is growth reported for urines
Pure growth
Predominant growth
- 2 different organisms -> usually ID both
Mixed growth
- 3+ colonies -> don’t ID these
What would you do with if a query E. coli and a uery Pseudo grew on the plate
Put up a purity plate for each
ID both organisms
Sens for both?
What would cause a very mixed growth on a plate?
Mostly just an incorrectly taken sample i.e. not a mid stream urine -> contains commensals
How could you tell if a sample was poorly taken?
Raised epithelial cells
Raised bacterial cells
Normal white blood cells
Mixed growth on plate if cultured
What would you do if there was predominant growth of E. Coli but the other organisms was a coag neg staph?
You can ignore the coag neg staph as this is probably just a commensal and just ID the E. Coli
What would you do if there was predominant growth of an E. Coli but the other organism was a query GNB
You must ID both organisms
Unlike with a coag neg staph you cannot assume the GNB is not the infectious agent - it probably isnt but just to be safe you must put up both
Why might there be no growth on a plate but urine was positive
Patient is probably on antibiotics i.e. the wccs and bacteria are high because they have an infection but the bacteria cannot grow just to the presence of antibiotics in the sample
The bacteria causing the infection could also be fastifious e.g. TB (rare) or Chlamydia
What would you do with a scanty growing organism where there is less than 10 colonies on the plate?
Less than 10 colonies is rarely ever infectious so unless it is a GNB we don’t pick it
Talk about E. Colis in urine
E. Coli is the most frequently seen bacteria causing UTIs
Grow as pinky/purple colonies on Chromagar
Query E. Colis don’t need to be Maldi’d before going for sens
Some E. Coli’s may be pale if they havent been able to produce their pink colour yet
What would you do with a white colony on a Brilliance chromagar
Query Staph/Query Yeast
S. aureus will be yellow coloured but a coag neg staph maybe white
Colonies will look spiky if query yeast
Staphyslide -> Staphaurex agglutination test -> S. aureus is coag pos, CNS or Yeast will be negative
Wet prep for yeast to look for budding
What is a wet prep?
Looking for budding yeast cells
Add 1 drop of saline to a glass slide
Pick up the query colonies with a glass coverslip and smear onto the slide
How will lactobacillus appear on Orientation agar
Lactobacillus can usually seen as a pink haze in the background agar
The lactobacillus is just a commensal
The background will be pink, colonies will not be pink (Not like E. Coli), pale colonies
What organisms do you send for Maldi ID?
All organisms other than E. Coli
What do you do after Maldi has ID’d your organism
See if the preliminary ID matches the Maldi ID -> if not then why
Write the ID of the organism on the plate
Will have to merge PID and Maldi ID for results e.g. ?GNB to Klebsiella etc
