Point-of-Care Versus Central Laboratory Measurements of Hemoglobin, Hematocrit, Glucose, Bicarbonate and Electrolytes: A Prospective Observational Study in Critically Ill Patients

Abstract

IntroductionRapid detection of abnormal biological values using point-of-care (POC) testing allows clinicians to promptly initiate therapy; however, there are concerns regarding the reliability of POC measurements. We investigated the agreement between the latest generation blood gas analyzer and central laboratory measurements of electrolytes, bicarbonate, hemoglobin, hematocrit, and glucose.Methods314 paired samples were collected prospectively from 51 critically ill patients. All samples were drawn simultaneously in the morning from an arterial line. BD Vacutainer tubes were analyzed in the central laboratory using Beckman Coulter analyzers (AU 5800 and DxH 800). BD Preset 3 ml heparinized-syringes were analyzed immediately in the ICU using the POC Siemens RAPIDPoint 500 blood gas system. We used CLIA proficiency testing criteria to define acceptable analytical performance and interchangeability.ResultsBiases, limits of agreement (±1.96 SD) and coefficients of correlation were respectively: 1.3 (-2.2 to 4.8 mmol/L, r = 0.936) for sodium; 0.2 (-0.2 to 0.6 mmol/L, r = 0.944) for potassium; -0.9 (-3.7 to 2 mmol/L, r = 0.967) for chloride; 0.8 (-1.9 to 3.4 mmol/L, r = 0.968) for bicarbonate; -11 (-30 to 9 mg/dL, r = 0.972) for glucose; -0.8 (-1.4 to -0.2 g/dL, r = 0.985) for hemoglobin; and -1.1 (-2.9 to 0.7%, r = 0.981) for hematocrit. All differences were below CLIA cut-off values, except for hemoglobin.ConclusionsCompared to central Laboratory analyzers, the POC Siemens RAPIDPoint 500 blood gas system satisfied the CLIA criteria of interchangeability for all tested parameters, except for hemoglobin. These results are warranted for our own procedures and devices. Bearing these restrictions, we recommend clinicians to initiate an appropriate therapy based on POC testing without awaiting a control measurement.

Concordance between point‐of‐care blood gas analysis and laboratory autoanalyzer in measurement of hemoglobin and electrolytes in critically ill patients

“…In these result pairs, the laboratory‐based Hb measurement tends to indicate blood transfusion 3‐4 times more frequently than BGA. This overestimation by BGA has been observed in previous studies …”

“…This overestimation by BGA has been observed in previous studies. 19 The blood glucose had small bias and limits of agreement; however, there were two observations of concern. Firstly, 7.1% of readings by the two methods were outside the US-CLIA variability limits, and secondly, the difference between the BGA and AA increased above 10 mmol, with BGA tending to overestimate blood glucose levels.…”

Point of care testing in general haematology

“…Similarly, a 2017 publication investigating the comparability of a blood gas analyser to the central laboratory method concluded that the methods could not be used interchangeably for Hb measurement where Clinical Laboratory Improvement Amendments of 1988 proficiency testing criteria (Centers for Medicare & Medicaid Services, ) was used to define interchangeability. The authors reported that Hb was systematically overestimated by the BGA by a mean of 8 g/l (Allardet‐Servent et al , ).…”

The accuracy of a point-of-care test among different operators using the QBC Autoread Plus Analyzer for the measurement of a basic full blood count

“…With regard to Hct, the Siemens RAPIDPoint (Siemens, Germany) POC system demonstrated a bias of −1.1 compared with the reference value. [9] In this study, nurses who were trained on the rapid point system performed the test in critically ill patients. Another POC instrument, the haemocytometer, was evaluated in an intensive care setting.…”