# Accuracy of Noninvasive Hemoglobin and Venous Blood Gas Hemoglobin Measurements in Comparison With the Laboratory Method in an Intensive Care Unit

## TL;DR

This study compares noninvasive and venous blood gas methods for measuring hemoglobin in ICU patients against lab results.

## Contribution

The study evaluates the accuracy of noninvasive hemoglobin monitoring in ICU settings compared to traditional lab methods.

## Key findings

- SpHb showed strong correlation with LabHb (r = 0.978) and acceptable bias.
- VBGHb had moderate correlation (r = 0.506) and larger bias compared to LabHb.
- SpHb demonstrated better trend accuracy than VBGHb in ICU patients.

## Abstract

Background

Rapid and accurate hemoglobin (Hb) measurement is crucial in Intensive Care Unit (ICU) patients for timely management of anemia and transfusion decisions. Noninvasive hemoglobin monitoring (SpHb) offers continuous assessment, while venous blood gas hemoglobin (VBGHb) provides point-of-care measurement. This study aimed to evaluate the absolute and trend accuracy of SpHb and VBGHb compared to standard laboratory hemoglobin (LabHb) in ICU patients.

Methods

Twenty patients in the ICU were enrolled. Hemoglobin was measured using SpHb, VBGHb, and LabHb. Absolute accuracy was assessed using Bland-Altman analysis, and correlation between methods was evaluated with Pearson correlation. Trend accuracy was assessed with modified Bland-Altman plots.

Results

A total of 79 samples were collected. SpHb demonstrated a mean bias of −0.0557 gm/dL (95% limits of agreement: −0.5614 to 0.4499) relative to LabHb, while VBGHb showed a larger bias of −0.4734 gm/dL (−2.8312 to 1.8844). SpHb had a strong correlation with LabHb (r = 0.978, p < 0.001), whereas VBGHb showed a moderate correlation (r = 0.506, p < 0.001). Trend analysis revealed a mean trend bias of −0.0102 gm/dL for SpHb (limits −0.6317 to 0.6113), compared with 0.0136 gm/dL for VBGHb (−3.5733 to 3.5461).

Conclusions

We concluded that SpHb demonstrated acceptable absolute and trend accuracy, as well as excellent correlation with LabHb, providing an easy, feasible, and accurate solution for Hb measurement in the ICU. Future studies should assess its impact on transfusion practices and patient outcomes.