Examination of a fresh urine specimen provides the best results. Bacteria will metabolize glucose and pH changes may occur, affecting these results that are reported as part of the macroscopic urine testing. If the specimen is dilute (specific gravity <1.010), and/or the pH is >7.0, casts, white blood cells and red blood cells may lyse. If an unpreserved specimen (i.e., specimen container does not contain a preservative) cannot be tested within two hours of collection, it should be refrigerated at 2°-8° C.
Although the most commonly received urine specimen is the random urine collection, the specimen of choice for urinalysis is the first morning urine. The first morning urine is more concentrated and allows for the detection of substances, which may not be present in a more dilute random sample.
Once the physical and chemical characteristics of the urine have been determined, the microscopic exam is performed on the sediment.
