Lab Tests & Expected Values in Hemodialysis | Monitoring Guide

πŸ”¬ Common Lab Tests in Hemodialysis Expected Values & Targets

Regular monitoring of adequacy, anemia, mineral metabolism, nutrition, electrolytes, and safety parameters

Hemodialysis patients require frequent laboratory monitoring to assess dialysis adequacy, manage complications, and adjust medications. Monthly testing is standard for most parameters, with some tests (Kt/V, iron studies) typically performed monthly or quarterly. Targets vary by guideline (KDOQI vs KDIGO).

πŸ“Š Dialysis Adequacy

  • spKt/V (Daugirdas): β‰₯1.4 (target), >1.2 (minimum)
  • URR (Urea Reduction Ratio): β‰₯70%
  • stdKt/V (weekly): β‰₯2.1 for thrice-weekly HD
  • nPNA (normalized protein nitrogen appearance): 1.0–1.2 g/kg/day (reflects protein intake)
πŸ“Œ Frequency: Monthly. Pre- and post-BUN with slow-flow or 30-min post draw.

🩸 Anemia Management

  • Hemoglobin (Hgb): 10–12 g/dL (avoid >13 g/dL)
  • Hematocrit (Hct): 30–36%
  • Ferritin: >200 ng/mL (target 200–800)
  • TSAT (Transferrin saturation): 20–50% (target >20%)
  • Iron (serum): 40–150 ΞΌg/dL
  • TIBC: 200–400 ΞΌg/dL
πŸ“Œ Frequency: Hgb monthly; iron studies monthly or quarterly.

🦴 Mineral & Bone Disorder (CKD-MBD)

  • Phosphorus (P): 3.5–5.5 mg/dL (KDOQI) / 2.5–4.5 mg/dL (KDIGO more strict)
  • Calcium (Ca, corrected): 8.4–10.2 mg/dL (avoid hypercalcemia)
  • iPTH (intact PTH): 130–600 pg/mL (KDOQI) / 2–9Γ— ULN (KDIGO)
  • 25-OH Vitamin D: β‰₯30 ng/mL (adequacy)
  • Alkaline Phosphatase (ALP): 30–120 U/L (bone fraction if elevated)
πŸ“Œ Frequency: Phosphorus, calcium monthly; PTH every 1–3 months.

πŸ₯— Nutrition & Inflammation

  • Albumin: β‰₯4.0 g/dL (BCG method) / β‰₯3.8 g/dL (BCP method)
  • Prealbumin: 30–40 mg/dL (more sensitive to recent intake)
  • Cholesterol: 100–200 mg/dL (low may indicate malnutrition)
  • CRP (C-reactive protein): <5 mg/L (lower better; elevated suggests inflammation)
  • nPNA (from Kt/V): 1.0–1.2 g/kg/day
⚠️ Albumin <3.5 g/dL is a strong predictor of mortality; triggers nutritional intervention.

⚑ Electrolytes & Acid-Base

  • Potassium (K⁺): 4.0–5.5 mEq/L (pre-dialysis)
  • Sodium (Na⁺): 135–145 mEq/L
  • Chloride (Cl⁻): 98–108 mEq/L
  • Bicarbonate (HCO₃⁻): 22–26 mEq/L (post-dialysis target)
  • Anion Gap: 8–12 (corrected for albumin)
  • Magnesium (Mg²⁺): 1.7–2.4 mg/dL
πŸ“Œ Frequency: Monthly (pre-dialysis). Potassium >6.0 triggers immediate review.

πŸ›‘οΈ Safety & Access Monitoring

  • BUN (pre & post): Used for Kt/V and URR
  • Creatinine (pre & post): Residual renal function marker
  • Uric Acid: 3–7 mg/dL (if gout, treat to <6)
  • Beta-2-microglobulin (Ξ²2M): Not routine; elevated in amyloidosis
  • Access flow (Transonic): AVF <600 mL/min = stenosis risk; AVG <800 mL/min
  • Recirculation: <10% (elevated suggests access stenosis)

πŸ“‹ Complete Laboratory Monitoring Schedule & Targets

TestTarget / Expected Value (HD Patients)FrequencyClinical Action if Abnormal
spKt/Vβ‰₯1.4Monthly<1.2 β†’ increase time/Qb/dialyzer size
URRβ‰₯70%Monthly<65% β†’ optimize prescription
Hemoglobin10–12 g/dLMonthly<10 β†’ increase ESA or iron; >13 β†’ reduce ESA
Ferritin200–800 ng/mLMonthly/Quarterly<200 β†’ IV iron; >800 β†’ hold iron, monitor overload
TSAT20–50%Monthly/Quarterly<20% β†’ IV iron
Phosphorus3.5–5.5 mg/dLMonthly>5.5 β†’ increase binders, diet review; <3.5 β†’ reduce binders
Calcium (corrected)8.4–10.2 mg/dLMonthly>10.2 β†’ reduce calcium-based binders, vitamin D analogs
iPTH130–600 pg/mL1–3 months>600 β†’ increase vitamin D analog; <130 β†’ reduce
Albuminβ‰₯4.0 g/dL (BCG)Monthly<3.8 β†’ nutrition consult, IDPN if severe
Potassium4.0–5.5 mEq/LMonthly>6.0 β†’ dietary review, increase dialysis; <3.5 β†’ dietary K supplementation
Bicarbonate22–26 mEq/LMonthly<22 β†’ increase dialysate bicarbonate; >28 β†’ reduce
25-OH Vitamin Dβ‰₯30 ng/mLQuarterly/Annually<30 β†’ prescribe cholecalciferol/ergocalciferol
Access flow (AVF)β‰₯600 mL/minMonthly<600 β†’ Doppler ultrasound for stenosis
Access recirculation<10%PRN (if Kt/V drops)>15% β†’ investigate access stenosis
Adapted from KDOQI 2020, KDIGO 2024 guidelines. BCG = bromocresol green method for albumin.

πŸ•’ Pre-Dialysis vs Post-Dialysis Specimens

Pre-dialysis (before session start):
  • BUN, creatinine, electrolytes (K, Na, Cl, HCO₃), Ca, P, albumin, CBC, iron studies, PTH
Post-dialysis (slow-flow or 30-min after):
  • BUN (for Kt/V), creatinine, phosphorus (not standardized), glucose, bicarbonate
⚠️ Critical error to avoid: Drawing post-BUN immediately after dialysis (without slow-flow) β†’ falsely high Kt/V β†’ underestimates underdialysis. Use slow-flow method (Qb 100 mL/min for 2 min) or 30-minute wait.
πŸ† Quality Indicators for Dialysis Units (CMS ESRD QIP):
  • Proportion of patients with spKt/V β‰₯1.4 (>90% target)
  • Proportion with hemoglobin 10–12 g/dL
  • Proportion with phosphorus ≀5.5 mg/dL
  • Proportion with albumin β‰₯4.0 g/dL (BCG)
  • Standardized mortality ratio (SMR)
  • Standardized hospitalization ratio (SHR)
  • Bloodstream infection rate (NHSN surveillance)

Regular lab monitoring and achieving targets directly correlate with improved survival and quality of life.