MLPAO Urinalysis and Body Fluids Advanced Practice Flashcards

What is the clinical significance of a low glucose level in pleural or peritoneal fluid?

Answer: Fluid glucose <3.3 mmol/L or fluid/serum ratio <0.5 suggests bacterial infection, tuberculosis, rheumatoid pleurisy, or malignancy

Low glucose in body fluids indicates consumption by bacteria (empyema, SBP), high metabolic activity of inflammatory cells (rheumatoid pleurisy, TB), or utilization by malignant cells. In pleural fluid, glucose <3.3 mmol/L is associated with complicated parapneumonic effusion requiring drainage. In ascitic fluid, low glucose suggests secondary bacterial peritonitis.

What is urine protein electrophoresis used for?

Answer: Characterizing the type of proteinuria (glomerular vs. tubular vs. overflow) and detecting Bence Jones protein

Urine protein electrophoresis separates urinary proteins to determine the pattern: glomerular proteinuria (albumin predominance), tubular proteinuria (low-molecular-weight proteins like beta-2 microglobulin), overflow proteinuria (abnormal proteins like Bence Jones), and mixed patterns. It is essential for detecting monoclonal light chains not found on routine dipstick.

What is the significance of positive lipase in pleural fluid?

Answer: Elevated pleural fluid lipase (above the upper limit of normal for serum) suggests pancreatitis-related pleural effusion or esophageal rupture

Elevated lipase in pleural fluid strongly suggests pancreatic pleural effusion (fistula between pancreatic duct and pleural space) or acute pancreatitis with sympathetic effusion. Amylase is also elevated in these cases and in esophageal rupture (salivary amylase). Pleural fluid lipase adds specificity for pancreatic origin.

What is the proper technique for body fluid cytocentrifugation?

Answer: Concentrate cells by centrifuging fluid in a specialized chamber that deposits a monolayer of cells onto a glass slide for staining and morphological examination

Cytocentrifugation (using a Cytospin centrifuge) concentrates cells from body fluids onto a defined area of a glass slide, creating a monolayer suitable for Wright-Giemsa staining and differential counting. This technique preserves cell morphology better than regular centrifugation and is essential for accurate differential counts on low-cellularity fluids.

What is the clinical significance of a positive urine drug screen?

Answer: It is a preliminary screening result that requires confirmatory testing (typically mass spectrometry) before clinical or legal decisions; false positives from cross-reacting substances are common

Urine drug screens (immunoassay-based) are screening tests with known cross-reactivities. False positives include: poppy seeds (opiates), decongestants (amphetamines), quinolones (amphetamines), and sertraline (benzodiazepines). Positive screening results must be confirmed by a definitive method (GC-MS or LC-MS/MS) before clinical, employment, or legal decisions are made.

What are the critical components of a joint fluid analysis in suspected septic arthritis?

Answer: Cell count (WBC typically >50,000/µL with >90% PMNs), Gram stain, culture, crystal examination, and glucose

Septic arthritis workup includes: 1) Cell count (WBC >50,000/µL with >90% neutrophils is highly suggestive), 2) Gram stain (positive in ~50% of bacterial cases), 3) Culture (blood and joint fluid), 4) Crystal examination (to rule out crystalline arthropathy, though infection and crystals can coexist), 5) Glucose (low in infection). Synovial lactate is an emerging marker.