Your recent ‘Ask the Experts’ article about using urinalysis to diagnose urinary tract infections made me realize that my doctor no longer includes a routine urinalysis in my annual checkup. Why is that?
You’re right that routine urinalysis has become less common. Studies have shown that it is not a very good screening test in asymptomatic people, as the chance of false positives is high.
For instance, it’s not so unusual to find trace blood in urine, as seen under a microscope (not detected by the naked eye). While it’s true that blood in urine can indicate cancer, this finding is more likely to be due to other things, including use of a medication (like an NSAID or anti-coagulant), heavy exercise, urethral stricture (scar tissue in the urethra from a past injury or STI, for instance), kidney or bladder stones, an enlarged prostate, a UTI, or simply menstruation. Sometimes, it ultimately has no explanation, despite follow-up testing.
Another reason urinalysis is no longer routine is that some of the conditions that it detects can be found earlier with blood tests, rendering the urinalysis somewhat redundant in those cases.
Still, urinalysis can provide some important clues. You might be asked to provide a urine sample to screen for diabetes or kidney or liver disease, for example, or if you are being monitored for such a chronic medical condition.
In addition to detecting possible signs of a urinary tract infection, a dipstick test checks the urine for blood, protein, sugar and ketones (a possible sign of diabetes), bilirubin (suggestive of liver disease or damage), and acidity (which could indicate a kidney or urinary tract disorder). The test uses a thin strip of plastic with chemicals that change color in in the presence of those substances.
Keep in mind, also, that even just a visual check of a urine sample can provide a wealth of information—it can reveal if you are dehydrated (ideally, urine is a pale not dark yellow), while a red or brown tint could indicate the presence of blood, and foamy urine could mean protein is present.
If you are giving a urine sample for whatever reason, be aware that your urine can be tinted various colors by certain vitamins and medications, and by some foods like beets and rhubarb. You should alert your provider about what supplements and medications you take and what you’ve eaten recently.
