Post-Filter Hematocrit (CRRTHCT)

Validation of a Post-Filter Hematocrit Calculation Formula: A Comparative Analysis With Measured Post-Filter Hematocrit Values

Filter clotting is a major complication of continuous renal replacement therapy (CRRT), resulting in blood loss, reduced treatment efficacy, and increased cost. One modifiable factor associated with filter clotting is filtration fraction (FF), or the proportion of plasma water being removed from the blood over the course of the filter. In convention, a cutoff of FF<20-30% has been used to prevent hemofilter clotting, but no evidence correlating FF with hemofilter clotting has been documented. Some experts have proposed that post-filter hematocrit (Hct) could be a more direct marker for determining hemofilter clotting risk, but evidence supporting clinical utility of this marker is lacking.

HCTpost=HCTpre/(FF(HCTpre-1)+1)

In our proposed validation study, we hope to determine whether our formula for post-filter Hct provides accurate results when compared to measured values. The information obtained from this study will potentially justify the use of utilizing the formula in future studies.

The procedure of this study is collecting blood samples from the post-filter lines of patients on CRRT at different time points and different flow rates. This will be considered the "measured post-filter hematocrit" which will then be compared to the calculated formula above, using the other values obtained from daily labs (for pre-filter hematocrit) and CRRT machine settings.

Study Overview

• Status: Recruiting
• Conditions: Renal Failure; Continuous Renal Replacement Therapy; Hemofilter Clotting
• Intervention / Treatment: Other: Calculated Post-Filter Hematocrit; Other: Measured Post-Filter Hematocrit

Detailed Description

This investigational study is listed as "other" because it is a validation study comparing two measurement methods-comparing a calculated versus a machine-measured post-filter hematocrit- and is typically classified as a cross-sectional investigational study in the context of diagnostic or method comparison research.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Gwyndolyn M Radford, MD; Phone Number: 7858179620; Email: gradford@uiowa.edu
• Study Contact Backup: Name: Benjamin R Griffin, MD; Phone Number: 5073631404; Email: benjamin-griffin@uiowa.edu

Study Locations

• United States
  • Iowa
    • Iowa City, Iowa, United States, 52242
      • Recruiting
      • University of Iowa Hospitals and Clinics
      • Contact: Gwyndolyn M Radford, MD; Phone Number: 319-384-9668; Email: gwyndolyn-radford@uiowa.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• patients initiated on CRRT age equal than or greater to 18 years of age

Exclusion Criteria:

• patients on ECMO

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: CRRT patients; All participants will receive the same "intervention" of both measuring and calculating post-filter hematocrit.	Other: Calculated Post-Filter Hematocrit; using the formula: HCTpost=HCTpre/(FF(HCTpre-1)+1); Other: Measured Post-Filter Hematocrit; Measured from blood sample taken from CRRT machine

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Agreement between measured and calculated post-filter hematocrit values.	Use Bland-Altman analysis to assess agreement and quantify bias and limits of agreement. Calculate correlation coefficients (Pearson or Spearman) to evaluate the strength of association.	Participation begins at consent and includes a single study procedure in which four post-filter blood samples are collected over ~40 minutes. Participation ends after the final draw. Generally, no longer than 1 day.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Analyze the impact of CRRT settings on discrepancies between measured and calculated Filtration Fraction	How do different settings (e.g., Q_B, Q_UF, Q_prefilter, Q_postfilter) on the machine affect the discrepancies (if there are any) between calculated and measured filtration fraction. Will be using change in post-filter hematocrit values as the measured filtration fraction and comparing to calculated filtration fraction using standard flow-rate derived formula used in practice.	Participation begins at consent and includes a single study procedure in which four post-filter blood samples are collected over ~40 minutes. Participation ends after the final draw. Generally, no longer than one day.
Subgroup analysis based on patient-specific factors	Post-filter hematocrit values will be stratified and compared across subgroups defined by baseline pre-filter hematocrit category, anticoagulation strategy (e.g., citrate vs. heparin vs. none), and blood-flow rate category. The metric reported will be the mean post-filter hematocrit within each subgroup and the between-group differences.	Participation begins at consent and includes a single study procedure in which four post-filter blood samples are collected over ~40 minutes. Participation ends after the final draw.

Collaborators and Investigators

• Sponsor: Gwyndolyn M. Radford

Study record dates

Study Major Dates

• Study Start (Actual): March 15, 2025
• Primary Completion (Estimated): February 1, 2026
• Study Completion (Estimated): March 15, 2026

Study Registration Dates

• First Submitted: March 4, 2025
• First Submitted That Met QC Criteria: December 7, 2025
• First Posted (Actual): December 19, 2025

Study Record Updates

• Last Update Posted (Actual): December 19, 2025
• Last Update Submitted That Met QC Criteria: December 7, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: continuous renal replacement therapy; filtration fraction; crrt; hemofilter clotting; post-filter hematocrit
• Additional Relevant MeSH Terms: Urogenital Diseases; Male Urogenital Diseases; Kidney Diseases; Urologic Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Renal Insufficiency
• Other Study ID Numbers: 202412294

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No