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