# Clinical Bedside Benchmarking Test for Measuring the Total Hemoglobin Concentration

## TL;DR

This study evaluates hemoglobin concentration measurement accuracy in ICU settings using various devices, focusing on low concentration ranges and providing uncertainty ranges for clinical use.

## Contribution

The study introduces practical prediction intervals for bedside hemoglobin measurements, translating lab accuracy into clinical practice.

## Key findings

- Strong concordance among devices was observed across hemoglobin concentration ranges.
- Systematic deviations were most notable at critically low hemoglobin levels (<6 g/dL).
- Prediction intervals for low concentrations were ±7% relative or ±0.38 g/dL absolute.

## Abstract

Objective: Accurate total hemoglobin concentration (ctHb) measurement is critical for clinical decision-making, particularly in acute care, where immediate therapeutic decisions are required. This study evaluated previously established laboratory-based accuracy criteria for ctHb measurements in routine clinical practice at an interdisciplinary operative intensive care unit (IO-ICU), and with particular attention to significantly reduced hemoglobin concentrations. Method: Remaining blood from blood gas analysis (BGA) cuvettes was collected directly at the ICU bedside. From these initial samples, three clinically relevant measurement scenarios were established: direct bedside measurement (Group 01), elevated ctHb levels (Group 02), and lowered ctHb concentrations below 9 g/dl (Group 03). The samples were analyzed using the GEM 4000, GEM 5000 (Werfen GmbH, Muenchen, Germany), ABL90 Flex plus (Radiometer GmbH, Krefeld, Germany), HemoCue Hb 201+, and XN 9000/9100 (Sysmex Deutschland GmbH, Norderstedt, Germany) automatic hematology analyzers. Since each measurement device inherently possesses systematic deviations, no single analyzer was defined as an absolute reference. Instead, the mean value across all tested measurement systems was utilized as a best-fit reference (REF) value. Results: A total of 120 data pairs from 40 ICU patients were analyzed using regression analyses, Bland and Altman (B&A) methods, and tolerance level analysis (TLA). The results demonstrated strong concordance among the evaluated measurement devices across the examined ctHb spectrum (~1–18 g/dL). Moderate systematic deviations identified by B&A analysis were most pronounced at critically low ctHb levels (<6 g/dL). A key outcome was the determination of 95% prediction intervals (PIs), representing a quantifiable range of uncertainties for future bedside measurements. The PIs for Group 03 “low” were in the range of ±7% (relative difference) or ±0.38 g/dL (absolute difference). Conclusion: This study effectively translates previous laboratory findings into clinical practice, highlighting the practical utility of PIs to guide the accurate interpretation of bedside ctHb measurements under acute care conditions.