What is the interpretation of urinalysis results?

From the Guidelines

Urinalysis should be interpreted in the context of clinical symptoms, and a positive result should not be relied upon solely for the diagnosis of urinary tract infections (UTIs), as the positive predictive value of pyuria for diagnosing infection is low 1. When interpreting urinalysis results, it is essential to consider the physical, chemical, and microscopic findings to identify potential health issues.

• First, examine color and clarity, with normal urine being pale yellow to amber and clear.
• Abnormal colors may indicate dehydration (dark yellow), blood (red/brown), bilirubin (tea-colored), or medications.
• Next, assess specific gravity (normal 1.005-1.030), which reflects hydration status and kidney concentrating ability.
• Check pH (normal 4.5-8.0), as alkaline urine suggests UTI while acidic urine may indicate metabolic conditions.
• Protein presence (proteinuria) warrants concern, potentially signaling kidney disease.
• Glucose (glycosuria) suggests diabetes or renal tubular dysfunction.
• Ketones indicate fat metabolism from starvation or diabetes.
• Bilirubin and urobilinogen abnormalities point to liver disease.
• Blood in urine (hematuria) may indicate infection, stones, or malignancy.
• Nitrites and leukocyte esterase suggest bacterial infection.
• Microscopic examination reveals cells, casts, crystals, and bacteria that provide further diagnostic information. Always correlate urinalysis findings with clinical presentation for accurate interpretation, as isolated abnormalities may be transient or clinically insignificant. The minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs 1. If pyuria (≥ 10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick, only then should a urine culture (with antimicrobial susceptibility testing) be ordered 1. In cases where urosepsis is suspected, urine and paired blood specimens should be obtained, if feasible, for culture and antimicrobial susceptibility testing, and a Gram stain of uncentrifuged urine should be requested 1. It is crucial to note that the diagnostic value of urinalysis for UTI is limited, and clinical symptoms should be the primary basis for diagnosis, with urinalysis findings used to support or rule out the diagnosis 1.

From the Research

Interpreting Urinalysis Results

• A complete urinalysis includes physical, chemical, and microscopic examinations, and the specimen should be examined within two hours of collection 2
• Cloudy urine can be caused by precipitated phosphate crystals in alkaline urine or pyuria, while a strong odor may be due to a concentrated specimen rather than a urinary tract infection 2
• Dipstick urinalysis is convenient but can produce false-positive and false-negative results, and specific gravity provides a reliable assessment of the patient's hydration status 2

Common Urinalysis Findings

• Microhematuria has a range of causes, from benign to life-threatening, and can be differentiated by other elements of the urinalysis 2
• Transient proteinuria is typically a benign condition, but persistent proteinuria requires further work-up 2
• Uncomplicated urinary tract infections can be diagnosed by positive leukocyte esterase and nitrite tests and treated without culture 2, 3

Urinalysis in Clinical Practice

• Urinalysis is a valuable tool in the initial evaluation of dysuria and other urinary tract symptoms 3
• Pyuria is the best determinate of bacteriuria requiring therapy, and values significant for infection differ depending on the method of analysis 3
• Automated urinalysis provides more sensitive detection of leukocytes and bacteria in the urine, and a value of > 2 WBC/hpf is significant pyuria indicative of inflammation of the urinary tract 3

Clinical Correlations and Interpretation

• Urinalysis is a widely used diagnostic tool to assist clinicians in determining the etiology of various acute or chronic pathologies 4
• Changes in urine concentration, acidification, protein, and sediment can be important in interpreting urinalysis results, particularly in common renal diseases of children 5