Theory and background
Urinalysis can be used as a screening test to aid detection of abnormalities and aid diagnosis, also for monitoring and management of a patient’s condition.
This may be performed routinely as part of health check, well woman / well man clinic or if indicated by patient history and presentation.
Urine Dipstick Analysis
There are a large range of sticks available, some are very specific eg. screen for glycosuria (the excretion of glucose in the urine).
Many have multiple tests on each strip, please check the test strips selected have the specific tests on that you require. Check that the container has not been left open and that the sticks are in date. Ensure that you are clear about the timings required for each test and that you know how to read the strip accurately. You must be familiar with the sticks you are using.
What can you test for?
Glucose is not normally present in the urine. Presence may be due to elevated blood glucose levels or reduced renal threshold.
Protein (Albumin) albumin and globulin is normally in too low a concentration to give a positive reaction. False positive results occur in strongly alkaline urine. Abnormal proteinuria (the presence of an excess of serum proteins in the urine) is usually due to glomerular disease, which may be caused by a variety of conditions, including diabetes mellitus and hypertension.
Blood suggests urological disease and/or urinary tract infection (UTI). Results may be false positive if the container is contaminated with bleach, perianal skin, povidone iodine, stale urine or menstruation.
pH Value is usually slightly acidic within pH 5-6 (range 4.8 to 8.5). Lowest after overnight fast, highest after meals. Can be helpful when screening for renal disease, respiratory disease, certain metabolic disorders and specific therapeutic regimens, such as sodium bicarbonate.
Nitrites are not normally present; produced by gram negative bacteria converting nitrates to nitrites. Ideally specimen should be obtained about 4 hours after last passing urine (voiding). Indicates a UTI and the sample should be sent for further testing.
Ketones are abnormal urinary constituents, being breakdown products of fatty acid metabolism.
Bilirubin indicates hepatic or biliary disease.
Urobilinogen is normally present in urine, elevated levels may indicate liver abnormalities or excessive destruction of red blood cells. Urobilinogen tests should be considered with the bilirubin result to provide a differential diagnosis. A false negative result may be obtained from a stale sample.
Leucocytes a positive result suggests pyuria (pus in the urine) associated with a UTI. Isolated results may not be significant. Repeated positives should not be ignored – but be aware of possible sources of contamination or other factors which may limit sensitivity to this test.
Specific Gravity (SG) sometimes called ‘density’. It is a laboratory test that measures the concentration of all chemical particles in the urine. Normal ranges given do vary between 1.001 -1.035 – so do check your product instructions carefully. Increased SG is seen in conditions causing dehydration, glycosuria or renal heart failure or inappropriate antidiuretic hormone secretion or proteinuria. Decreased SG may be seen in excessive fluid intake or renal failure or pyelonephritis.
Tests can be falsely positive or falsely negative so remember to be aware of other factors…
Consider whether –
The sample could have been contaminated?
The patient’s medication could have affected the results or the sensitivity of the test?
The patient’s condition could have affected the results or sensitivity of the test?