The urinalysis is the most important initial study in the evaluation of the patient suspected of having a UTI. A negative urinalysis makes the diagnosis of UTI unlikely. A simple midstream sample voided into a sterile container is sufficient and the more difficult and elaborate clean-caught midstream urine has not been found to be superior.
If the urine sample cannot be examined within 10 -15 minutes of obtaining it, it must be refrigerated. Uncentrifuged urine can be examined with a microscope (immersion lens) under a cover slip. The finding of bacteria by this method has a 90% correlation with the culture of > 1 million bacteria/ mL. In women the finding of greater than 7 white cells per high power field is suggestive of infection while the absence of this finding makes this diagnosis unlikely. In men the presence of any number of white cells should be considered
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