A complete urinalysis evaluates several different aspects of your urine through physical, chemical, and microscopic examination. In lupus treatment, a urinalysis is often used to monitor protein leakage and identify and assess urinary tract infections (UTIs). Most people with kidney lupus (lupus nephritis) will have an abnormal urinalysis. Protein, urine casts (especially red blood cell casts), red blood cells, or white blood cells in the urine can indicate serious kidney involvement; leukocyte esterase may indicate a bladder infection. Urine samples can be given at any time while at the doctor’s office. A urine culture is performed to assess for a bladder infection and to determine appropriate antibiotics. Before giving a urine sample, ask a medical professional to counsel you on how to prevent contamination. Several analytical elements of the complete urinalysis are explained below. Physical Examination / MacroanalysisIn this portion of the analysis, the color, clarity, and concentration of the urine are evaluated. Abnormal colors can result from disease, certain foods, or contamination, so the physical examination is generally viewed as a crude assessment. Light or dark coloration also suggests how much water is being excreted. The clarity of urine is measured as either clear, slightly clear, cloudy, or turbid. Urine clarity, like urine color, suggests that substances may be present in the urine; for example, turbid urine suggests the presence of protein or excess cellular material. However, accurate conclusions regarding the origin of the urine clarity cannot be drawn until further chemical and microscopic tests are performed. The physical examination also includes specific gravity, which measures the concentration of the urine sample. Specific gravity compares the concentration of urine to that of water (1.000). Usually it is better for the urine given in a sample to be more concentrated; this allows the laboratory to more accurately detect substances being excreted by your body. If your urine is very dilute (i.e., you have been drinking lots of water or receiving fluid via IV), you may be asked to give another urine sample. Chemical AnalysisThe chemical examination measures several features of the urine. Most laboratories use chemical test strips (“dipsticks”) that change colors when dipped into the urine. Either the laboratory technician or an automated instrument will then read the reaction color for each test pad to determine the result for each test. The use of automated instruments helps to eliminate discrepancies that arise with human interpretation.
Microscopic AnalysisThe microscopic examination uses a microscope to identify and count cells, crystals, bacteria, mucous, and other substances that may be present in the urine. The amount of a substance present is reported one of two ways: as a count with the microscope strength used to view the substance [“per low power field” (LPF) or “per high power field” (HPF)], or as an approximate amount (“rare,” “few,” “moderate,” or “many”).
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