MLPAO Urinalysis and Body Fluids Advanced Practice 2 — Questions and Answers
Question 1: What are the different types of peritoneal fluid analysis performed in suspected spontaneous bacterial peritonitis (SBP)?
- Cell count only
- Cell count with differential (WBC >250 neutrophils/µL diagnostic), protein, albumin, glucose, LDH, Gram stain, and culture (in blood culture bottles) (Correct answer)
- Culture in standard tubes only
- pH measurement only
Correct answer: Cell count with differential (WBC >250 neutrophils/µL diagnostic), protein, albumin, glucose, LDH, Gram stain, and culture (in blood culture bottles)
SBP diagnosis is based on ascitic fluid polymorphonuclear (PMN) count >250 cells/µL. Additional analysis includes total protein, albumin (SAAG = serum albumin - ascitic albumin; >11 g/L suggests portal hypertension), glucose, LDH, Gram stain, and culture. Inoculating ascitic fluid into blood culture bottles at the bedside increases culture sensitivity from ~50% to ~80%.
Question 2: What is the significance of xanthochromia in cerebrospinal fluid?
- It indicates bacterial meningitis
- A yellow discolouration of CSF supernatant indicating the presence of hemoglobin degradation products (bilirubin, oxyhemoglobin), suggesting subarachnoid hemorrhage at least 2-4 hours old (Correct answer)
- It is a normal CSF colour
- It indicates viral meningitis
Correct answer: A yellow discolouration of CSF supernatant indicating the presence of hemoglobin degradation products (bilirubin, oxyhemoglobin), suggesting subarachnoid hemorrhage at least 2-4 hours old
Xanthochromia (yellow discolouration of CSF supernatant after centrifugation) indicates in vivo hemoglobin degradation, distinguishing subarachnoid hemorrhage (SAH) from traumatic tap. It develops 2-4 hours after SAH as RBCs lyse and hemoglobin is converted to oxyhemoglobin and then bilirubin. Spectrophotometric analysis provides objective xanthochromia assessment.
Question 3: What is the serum-ascites albumin gradient (SAAG) and how is it used?
- A urine test for kidney disease
- SAAG = serum albumin - ascitic fluid albumin; ≥11 g/L indicates portal hypertension; <11 g/L indicates non-portal hypertensive causes (Correct answer)
- A blood test for liver function
- A CSF analysis parameter
Correct answer: SAAG = serum albumin - ascitic fluid albumin; ≥11 g/L indicates portal hypertension; <11 g/L indicates non-portal hypertensive causes
SAAG is calculated by subtracting the ascitic fluid albumin from the serum albumin. A SAAG ≥11 g/L (1.1 g/dL) indicates portal hypertension with 97% accuracy (cirrhosis, heart failure, Budd-Chiari). SAAG <11 g/L suggests non-portal hypertensive causes (malignancy, TB peritonitis, nephrotic syndrome, pancreatitis). SAAG has replaced the traditional transudate/exudate classification for ascites.
Question 4: How should a CSF specimen be prioritized if the volume is limited?
- Culture first, then cell count, then chemistry
- Cell count and differential first (tube 1), then chemistry/serology (tube 2), then microbiology (tube 3 — least likely contaminated) (Correct answer)
- Chemistry first, then culture, then cell count
- All tests have equal priority
Correct answer: Cell count and differential first (tube 1), then chemistry/serology (tube 2), then microbiology (tube 3 — least likely contaminated)
When CSF volume is limited, prioritization depends on clinical suspicion. Generally: Tube 1 (cell count — most affected by traumatic tap, so use first tube), Tube 2 (chemistry/protein/glucose), Tube 3 (Gram stain and culture — last tube is least contaminated by blood from traumatic tap). However, if meningitis is strongly suspected, microbiology may take priority.
Question 5: What is the significance of finding eosinophils in a pleural fluid?
- Normal finding in all effusions
- Pleural eosinophilia (>10% eosinophils) suggests parasitic infection, drug reaction, malignancy, or prior pneumothorax/hemothorax (Correct answer)
- It indicates bacterial pneumonia
- It has no diagnostic significance
Correct answer: Pleural eosinophilia (>10% eosinophils) suggests parasitic infection, drug reaction, malignancy, or prior pneumothorax/hemothorax
Pleural eosinophilia (>10% eosinophils in pleural fluid) has a specific differential diagnosis including parasitic infection, drug-induced pleuritis, malignancy (especially lymphoma), and prior air or blood in the pleural space. It notably makes tuberculosis very unlikely (<1% of TB effusions have eosinophilia), which can be diagnostically useful.
Question 6: What automated method is used for urine chemistry in high-volume clinical laboratories?
- Manual dipstick reading only
- Automated urine chemistry analyzers (Clinitek Atlas, Atellica, Cobas u701) that use reflectance photometry to read and standardize dipstick results (Correct answer)
- Mass spectrometry
- Flame photometry
Correct answer: Automated urine chemistry analyzers (Clinitek Atlas, Atellica, Cobas u701) that use reflectance photometry to read and standardize dipstick results
Automated urine analyzers use reflectance photometry to objectively read reagent strip colour changes, eliminating the subjectivity of manual visual reading. Instruments like the Roche Cobas u701, Siemens Clinitek, and Beckman Atellica standardize timing, minimize human error, and provide consistent semi-quantitative results with audit trails.
MLPAO Urinalysis and Body Fluids Advanced Practice 2
What are the different types of peritoneal fluid analysis performed in suspected spontaneous bacterial peritonitis (SBP)?