YEAR 1 - Clinical Chem Overview

Urinalysis Overview

• Urinalysis involves testing urine through macroscopic evaluation, physical measurements, chemical reagent testing, and microscopic examination.
• Aids in diagnosing diseases, screening for conditions, monitoring disease progression, and evaluating therapy effectiveness.
• All specimens treated as infectious; Standard Precautions must be followed.

Specimen Collection

• Emphasis on hand washing and proper cleanliness is essential.
• Specimens must have secure lids to prevent leakage.

Types of Specimens

• Random Specimens: Collected anytime; time of voiding is recorded to account for diurnal variation.
• First Morning Specimen: Collected first thing in the morning; most concentrated and reliable for chemical analysis.
• Timed Specimen: Collected at specific times; important for stringent transport conditions.

Specimen Preservation

• Preservation prevents decomposition; low pH and high specific gravity can slow deterioration.
• Urine can decompose within 20-30 minutes due to bacteria producing ammonia.
• Refrigerated specimens without preservatives should not be analyzed after 48 hours.
• Boric Acid: Common preservative that reduces false positives by deterring bacterial growth.
• Other preservatives include HCL, Chlorohexidine, and Formalin for various needs.

Specimen Requirements/Acceptability

• High-quality specimens essential for accurate results; preferred first morning specimens should be tested within 2 hours of collection.
• Urine should be shielded from light to prevent degradation of sensitive constituents.
• Minimum volume for analysis is usually 12mL, preferably 50mL, with sterile, leak-proof containers required.

Protein Testing in Urine

• Increased protein levels may indicate renal disease; affected by physical exercise or fever.
• Urinalysis test strips are sensitive primarily to albumin; correlation with specific gravity is crucial.
• False Positives: Can occur due to alkaline pH, prolonged dipstick exposure, cleaning agents, blood, or high bilirubin levels.
• False Negatives: May result from diluted urine or the presence of proteins other than albumin.

Glucose and Reducing Substances

• Glycosuria/Glucosuria: Indicates significant glucose presence; depends on blood glucose levels and filtration/reabsorption issues.
• Glomerular permeability changes can lead to abnormal substance loss.

Sigma Quality Control (QC)

• Six Sigma level indicates high precision, equating to 3 errors per million tests.
• Three Sigma suggests lower precision with more errors (26,674 per million).
• QC rules minimize errors; fewer rules required when assay accuracy is high.
• Sigma calculation involves total allowable error, bias, and coefficient of variation.

Method Evaluation

• Lab methods and equipment must meet specific criteria before patient testing.
• Evaluation is necessary for outdated methods or analyzers.
• Most laboratory methods today are commercially developed, emphasizing the need for linearity in testing.

This quiz explores the essentials of urinalysis, including specimen collection techniques and preservation methods. Participants will learn about different types of urine specimens and the importance of maintaining cleanliness during collection. Mastering these concepts is crucial for effective disease diagnosis and monitoring.