Urinalysis and Body Fluids Overview

Introduction

Overview of the identification of insoluble substances (formed elements) in urinalysis.

Red Blood Cells (RBCs): Cells present in urine that indicate possible bleeding in the urinary tract.
White Blood Cells (WBCs): Cells indicative of inflammation or infection.
Epithelial Cells: Cells that line the urinary tract, which can indicate sloughing or damage.
Casts: Aggregates of protein or cells that form in the renal tubules; critical for identifying kidney pathology.
Bacteria: Presence indicates urinary tract infections.
Yeast Parasites: Fungal elements that can suggest infection, particularly in immunocompromised patients.
Mucus: May be present in normal urine, indicating excretory function.
Spermatozoa: Presence can indicate contamination from sexual activity.
Crystals: Solid form elements that can form from various conditions, affecting urine pH and solubility.
Artifacts: Unwanted particles or contaminants that can mimic pathological findings.

Sieving Process: Microscopic examination is based on results from macroscopic examination, focusing on physical and chemical characteristics.
Aspects assessed:
- Color: Indicates possible pathological conditions.
- Clarity: Turbidity can suggest infections or other issues.
- Blood: May indicate bleeding.
- Protein: Can indicate kidney damage.
- Nitrite: Presence suggests bacterial infection.
- Leukocyte Esterase: Indicates white blood cells and potential infection.
- Glucose: Could imply diabetes when present.
Special populations require special considerations, including:
- Pregnant Women
- Pediatric Patients
- Geriatric Patients
- Diabetic Patients
- Immunocompromised Patients
- Renal Patients
Copyright © 2008 EA Davis Company

Testing is often requested by physicians.
Criteria based on laboratory-specified populations.
Any abnormal physical or chemical findings trigger further investigation.
Laboratory criteria integrated into automated instrumentation lowers manual error rates.
Copyright © 2008 EA Davis Company, Urinalysis and Body Fluids, 5th Edition

Procedures include:
- Preparation of Sediment: Technique to prepare urine for examination under the microscope.
- Volume of Sediment Examined: Standard volume to analyze for accurate results.
- Methods of Visualization: Ensures clarity and accuracy in visual assessment.
- Reporting of Results: Uniform reporting standards help convey findings effectively.
Use of commercial systems such as KOVA aids in standardization.
Equipment includes:
- Calibrated centrifuge tubes.
- Specially designed slides for controlling volume.
- Decanting pipettes to transfer liquid without disturbing sediment.
- Grids for more accurate quantitation of formed elements.
Copyright © 2008 EA Davis Company, Urinalysis and Body Fluids, 5th Edition

Screening Test and Significance:
- Color: Correlates with specific pathologies.
- Clarity: Essential to confirm pathologic or nonpathologic causes of turbidity in samples.
- Blood:
- Differentiation between hematuria (RBCs) versus hemoglobinuria or myoglobinuria.
- Protein Presence: May signify casts or cellular elements in sediment.
- Nitrite: Indicates bacterial infection thru the presence of bacteria and WBCs.
- Leukocyte Esterase: Indicates WBC casts and bacterial infections.
- Glucose: Often correlates with the presence of yeast in urine.

Ideally, specimens are examined when fresh or properly preserved to maintain cellular integrity.
Important considerations include:
- RBCs, WBCs, and casts may lyse in dilute, alkaline urine.
- Refrigeration can precipitate crystals, affecting results.
- A midstream clean-catch specimen minimizes contamination, particularly with epithelial cells.
- Mixing the specimen prior to decanting into centrifuge tubes is essential for accurate analysis.

Centrifuge Volume: Recommended 10-15 mL of urine; reagent strips require at least 12 mL for effective testing.
Tubes should always be capped to maintain sample integrity.
Insufficient volume yields fewer formed elements, complicating the analysis.
Some laboratories adjust results based on the volume processed.

Standardization of centrifugation is crucial:
- Recommended speed and time: 5 minutes at a relative centrifugal force (RCF) of 400.
- RCF accounts for variations in centrifuge head diameter, unlike revolutions per minute (rpm), which is less reliable.
- It is important not to brake the centrifuge to avoid disturbing sediment, ensuring accuracy of results.