Urinalysis
Interpreting other clinically relevant results
Leucocytes
Testing for leucocytes involves the detection of white blood cells within the sample. Normally this should be negative. Presence of leucocytes would usually indicate a urinary tract infection.
Nitrites
Under normal circumstance there should be no nitrites in the urine. Many gram negative organisms (which are the pathogens which commonly cause urinary tract infections) convert nitrates present in normal urine to nitrites. Therefore the presence of nitrites would indicate an infection. If absent however, it does not exclude infection as not all bacteria are able to perform the reaction.
Ketones
Ketones are not usually present in urine. They are produced during fat metabolism. The presence of ketones could suggest fasting (starvation) especially if accompanied by fever and vomiting as in diabetic ketoacidosis with grossly uncontrolled type 1 diabetes.
Other Factors Tested for With Urinalysis
Listed below are some other factors which you may see on the urine test strip. Some information is given on each, although in general they are less clinically relevant
- Specific gravity is a measure of how dense or concentrated the urine sample is. It is not often use clinically. Very high values may indicate dehydration, whilst very low values may suggest a high fluid intake.It can be used during urine testing of athletes for substance misuseto ensure that the urine is not too dilute for testing.
- pH of the urine can vary and the normal range is from 4.6 to 8.0. It can be altered by dietary intake. Low values may occur in diabetic ketoacidosis or starvation. Over time persistently acidic urine may predispose the individual to the formation of renal tract calculi. High values may indicate a stale urine specimen or a urinary tract infection.
- Bilirubin is a breakdown product of haemoglobin. It may be present in urine at an extremely low concentration, but not in sufficient quantities to be detected by a urine dipstick. Therefore a positive result should be regarded as abnormal and may indicate liver disease.
- Urobilinogen is a breakdown product of bilirubin and is normally present in small concentrations. A high result again may indicate liver disease.