Invasive and non-invasive point-of-care testing and point-of-care monitoring of the hemoglobin concentration in human blood – how accurate are the data?

Abstract

In this review, scientific investigations of point-of-care testing (POCT) and point-of-care monitoring (POCM) devices are summarized with regard to the measurement accuracy of the hemoglobin concentration. As a common basis, information according to the Bland and Altman principle [bias, limits of agreement (LOA)] as well as the measurement accuracy and precision are considered, so that the comparability can be mapped. These collected data are subdivided according to the manufacturers, devices and procedures (invasive and non-invasive). A total of 31 devices were identified. A comparability of the scientific investigations in particular was given for 23 devices (18 invasive and five non-invasive measuring devices). In terms of measurement accuracy, there is a clear leap between invasive and non-invasive procedures, while no discernible improvement can be derived in the considered time frame from 2010 to 2018. According to the intended use, strict specifications result from the clinical standards, which are insufficiently met by the systems. More stringent requirements can be derived both in the area of blood donation and in the treatment of patients.

Current Status of Measurement Accuracy for Total Hemoglobin Concentration in the Clinical Context

“…However, this form of overview has two major blind spots: firstly, the systematic measurement error of the reference is negated, and secondly, an evaluation of the measurement accuracy in the form of a representative zone is not provided for a range below 6 g/dL. The TLA form of representation was an attempt to close these blind spots [ 7 ]. This is based on the B and A principle that every device or process will show some systematic error.…”

“…In contrast to the error grid representation of Clark [ 16 , 39 ] we selected the TLA as representative due to the obvious advantages of this method. In particular, these take into account tHb values below 6 g/dL and the consideration of potential systematic errors regarding the measurement methods [ 7 ]. As with the error grid representation, representative zones are defined.…”

“…Zone A represents the requirements for detecting anemia, zone C is defined by the accuracy requirements for patent blood management, zone E is defined as the critically low area requiring the most accurate measurements. Zones B and D represent a seamless transition between the critical zones, according to [ 7 ].…”

“…The accuracy of the total hemoglobin concentration (tHb) measurement (tHb in g/dL) is a fundamental requirement for decision-making. Red blood cell transfusion is associated with significant risks, and the number of blood donors is declining [ 4 , 5 , 6 , 7 ]. With adequate monitoring, significantly lower tHb levels can be tolerated clinically [ 2 , 8 ].…”

“…This applies over the entire measuring range and even more so to ranges of 3–9 g/dL. As instrument candidates, the methods of the relative differences in relation to the corresponding reference values within the limits < +/− 5% and the tolerance level analysis (TLA) [ 7 ] meet the requirements for testing with respect to these adjusted limits.…”