CDN Diagnostics Flashcards: 50 Practice Questions & Answers

Interpretation: Immune due to vaccination. Rationale: The presence of Anti-HBs (Surface Antibody) ≥10 mIU/mL without Anti-HBc (Core Antibody) indicates successful immunization. Dialysis-specific protocol: These patients do not require monthly HBsAg screening. Per CDC and NNCC guidelines, Anti-HBs levels should be retested annually. If the titer falls below 10 mIU/mL, a booster dose is required. Exam Tip: Only HBsAg-positive patients require physical isolation; immune patients can be treated in the general population.

Formula: % Recirculation = (P - A) / (P - V) x 100. Calculation: (80 - 70) / (80 - 10) = 10 / 70 = 14.3%. Clinical Significance: Yes. Recirculation >10% using the urea method (or >5% using non-urea methods) is clinically significant and requires investigation for venous stenosis. NNCC Tip: Ensure you subtract arterial from peripheral in the numerator; reversing these is a common exam distractor.

eKt/V accounts for urea rebound, which is the movement of urea from the intracellular/interstitial spaces into the intravascular space post-dialysis. spKt/V assumes urea is in a single compartment and overestimates clearance because it doesn't account for this lag. Exam Tip: NNCC tests the rebound concept as the primary reason for this numerical difference, reflecting a more accurate delivered dose to the whole body. Clinical Pearl: eKt/V is especially important in high-efficiency, short-duration treatments where the rebound is more pronounced.

URR = [(Pre - Post) / Pre] x 100. Calculation: [(80 - 20) / 80] = 60 / 80 = 0.75 or 75%. The minimum KDOQI goal for URR is 65%. This patient meets the adequacy goal. Clinical Pearl: While URR is a simple measure of urea clearance, it does not account for the contribution of ultrafiltration to solute removal, which is why Kt/V is often preferred for a more comprehensive assessment. On the CDN exam, remember that a URR of 65% is roughly equivalent to a spKt/V of 1.2.

This patient is a High Transporter (D/P >0.81). High transporters achieve rapid equilibration between blood and dialysate. While they have excellent small-solute clearance (creatinine/urea), they experience rapid glucose absorption, leading to a quick loss of the osmotic gradient and poor UF during long dwells. Exam Tip: High transporters often require shorter, more frequent dwells (APD/CCPD) to maximize UF and prevent fluid overload.