Urine dipstick Flashcards
what is definition pyuria
> 10 WBC per mm3
UTI definition
MSU
SP aspirate
more than 10 to 5 CFU per ml or more than 5 bacteria per HPF
any bacteria in SP aspirate
dipstick haematuria definition
more than 3 RBC per HPF
leucocytes false positive reasons 3
rifampicin
glucosuria
nitrofurantoin
how is haematuria detected
oxidation of a chromagen by peroxidase activity of hb on a substrate orthotolidine
colour change on strip compared to known standards
The chromogen indicator on the dipstick orthotolidine is a peroxidase substrate
When haemoglobin comes into contact with orthotolidine an oxidation reaction takes place resulting in colour change blue colour of indicator
false negative cause of haematuria
due to red cell lysis in transit from community vitamin c (reducing agent) captopril ph less than 5.1 proteinuria
false positive haematuria
myoglobinuria bacterial peroxides povidone menstruation exercise dehydration
definitiion of NVH
more than 3 RBC per HPF according to AUA in 2 of 3 samples
or more than 5 RBC per microlitre in nephrology
prevalence of NVH
8% of women and 2.5% men working age
haematuria screening studies
britten 1992
16-20% of dipstick will have NVH in men 50-60 of which 5-8% will have cancer
risk of UC in patients with negative investigations for VH
near zero in first 6 years
incidence of cancer in NVH
70% of NVH no abnormality found
5% yield
Prince study 2014
5000 bladder cancer patients compared with >20000 matched controlled to estimate PPV
PVV was highest for wcc and dysuria
any haematuria risk of UC
10%
with 7.5% stone disease
VH risk Urinary tract cancer
13%
9.2% stone disease
NVH risk urinary cancer
3% of which 0% UTUC
4.3% stone disease
causes urine colour orange red green blue brown
sulfasalazine orange
red - haematuria, rifampicin, chronic lead poisoning
green blue - methylene blue, metronidazole, nitrofurantoin
brown - urobilinogen, porphyria, metronidazole, nitrofurnatoin
chromogen indicator for hb name
colour change
time taken
orthotolidine
is a peroxidase substrate
to green
wait 60 seconds
dipstick haematuria
+
++
+++
10 25 50 150 250
leucocyte test on dipstick
colour change
leucocyte esterase activity of neutrophils
hydrolysis
released by WBC neutrophils
hydrolysis of substrate on dipstick to produce indoxyl which oxidizes diazonium salt chromogen
change to violet
Enzyme causes hydrolysis of an indoxyl carbonic acid ester - the substrate on dipstick – to indoxyl which in turn oxidizes a diazonium salt chromogen on dipstick to produce colour change
substrate name for wcc
indoxyl carbonic acid ester
diazonium salt chromagen
wait 2 minutes
how to do urine dipstick
. Check the expiry date of the urinalysis dipstick.
- Remove a dipstick from the container whilst avoiding touching the reagent squares.
- Replace the container lid to prevent oxidisation of the remaining dipsticks.
- Insert the dipstick into the urine sample, ensuring all reagent squares are fully immersed.
- Remove the dipstick immediately and tap off any residual urine using the edge of the container, making sure to hold the dipstick horizontally to avoid cross-contamination of the reagent squares.
- Lay the dipstick flat on a paper towel.
- Use the urinalysis guide on the side of the testing strip container to interpret the findings. Different reagent squares on the strip need to be interpreted at different times, so ensure you interpret the correct test at the appropriate time interval (e.g. 60 seconds for protein).
- Once you have interpreted all of the tests, discard the strip into the clinical waste bin along with your PPE.
- Wash your hands.
time to interpret wcc
2 minutes
false positive WCC
contanmination eg vaginal discharge
false negative WCC
glucosuria rifampicin nitrofurantoin old specimen (leucocyte lysis) dehydration vit c urobilinogen
left too long white cell lysis
read under 2 mins
number of wcc detected for positive
> 10 wbc per hpf
wcc sens and sepc
sen 70-90%
spec 40-80%
PPV 50%
NPV 90%
combined 75-80% 80-90% spec
nitrites spec 92%-100% sensitivty 30-70%
nitrates test react with what reagent to form what bacteria convert colour change reagent name
most bacteria convert nitrates to nitrities not usually present in urine react with aromatic amine reagent to form a diazonium salt colour change pink urinary nitrates to nitrites
Nitrites react with aromatic amine reagent on the dipstick to form a diazonium salt
The salt then reacts with hydroxybenzoquinolone to form a pink coloured azo dye (Griess reaction)
time taken nitrate test
colour change
60 second
to pink
why need close diptstick container
nitrate reagnet sensitive to air exposure
containers should be closed
false negative nitrite test
may miss grame positive inc pseudonomas
short transit time diuresis less than 4 hours
nitrates sens and spec
sens 20-40%
spec 90-100%
PPV 80%
NPV 80%
combination leuc and nitrate test sens and spec
more spec but less sensitivie than each test alone
sens 75%-84%
spec 82-98%
nitrates false negative
gram positive transit time <4 hours urine in bladder elevated urobilinogen vitamin c ph less than 6 elevated SG
protein test
reagent
colour change
bromophenol blue
sensitive for albumin
to blue green colour
usual permeability for proteins
less than 20kD only peremeable
proteinuria definition more than mg per day
more than 150mg per day i.e. 10-20mg per dl
protein dipstick plus number to amount of protein
1+ = 30mg protein per dl and is considered positive
2+ 100
3+ 300
4+ to 1000 mg per dl
RTA unable to acifidy to
type I
type II
The inability to acidify urine to a pH of less than 5.5 despite an overnight fast and administration of an acid load is the hallmark of RTA.
In type I (distal) RTA, the serum is acidic but the urine is alkaline, secondary to an inability to secrete protons into the urine. Type II (proximal) RTA is characterized by an inability to reabsorb bicarbonate. This situation initially results in alkaline urine, but as the filtered load of bicarbonate decreases, the urine becomes more acidic.
urinary crystals coffin lid envelope barrel shaped hexangonal
coffin lid - MAP
envelope calcium oxalate
hexagonal cystine
uric acid diamond or barrel shaped
urine ph normal range
5.5 to 6.5
when suggest stones with urine ph
ph >7.5 with UTI
why alkaline urine associated with CAP stones
urease bacteria catylyses urea to co2 and ammonia, which raises urinary PH, alkalinity causes precipitation of calcium mag ammonium phosphate staghorn stones
how much protein excreted daily
80 to 150mg excreted daily
protein dipstick test substance
tetrabromophenol turns blue with albumin more than 20mg/dl
protein dipstick test substance
tetrabromophenol turns blue with albumin more than 20mg/dl
false negatives protein test
bence jones
dilute urine
high PH
false negatives protein test
bence jones
dilute urine
high PH
glucose normal conditions renal reabsorption threshold
180mg/dl
urine dipstick glucose reaction
double oxidation of glucose results in colour change
preparation MSU how much pass first before mid stream circumcised uncirmcumcised women
circumcised
no prep, pass more than 100mls then collect urine
uncirmcumcised
retract , wash glans soap then void as above
women
retract labia, clean periurethral are soap, provide sample
preparation sample microscopy
5-10mls cetrifuged for 5 mins
IDENTIFY study
> 11,000 patients
All cancers
Any Haematuria 20%
VH 26%
NVH 6%
No bladder cancer in NVH under 35
no UTUC in NVH under 60
items on urine dipstick
leuc 2 mins nit urobilinogen protein ph blood SG 45 seconds ketones bilirubin 30 seconds glucose 30 seconds
