Preanalytical conditions of point-of-care testing in the intensive care unit are decisive for analysis reliability

Abstract

BackgroundPoint-of-care testing (POCT) systems enable a wide range of tests to be rapidly performed at the bedside and have attracted increasing interest in the intensive care unit (ICU). However, previous studies comparing the concordance of POCT with central laboratory testing have reported divergent findings. Most reported studies on POCT reliability have focused on analyzer performance rather than the preanalytical phase. The aim of this study was to assess the reliability of results provided by point-of-care analyzers according to the organization of the care units and the preanalytical process.MethodsIn three adult critical care units, 491 paired blood samples were analyzed for hemoglobin, potassium, and sodium concentrations by blood gas analyzers (identical reference) and the central laboratory. The clinical significance of agreement was assessed using Bland–Altman plots. A quality improvement program was then implemented to improve the preanalytical POCT process for one ICU where there was poor agreement. A second comparison was performed on 278 paired blood samples in this unit.ResultsBiases were clinically nonsignificant for potassium and sodium concentrations for all tested critical care units, relative to the reference method. However, biases [limits of agreements] for hemoglobin analyses were clearly affected by the preanalytical process: −3 [−6; 1] g/L in the operating room, −5 [−28; 17] g/L in a 10-bed ICU, and −19 [−64; 27] g/L in a 37-bed ICU. The quality approach was implemented in the 37-bed ICU and led to corrective actions that: (1) reduced the time for the POCT preanalytical phase; (2) implemented a checklist to validate the preanalytical conditions; (3) used technical innovations. The improvement of the preanalytical process resulted in a substantial decrease of the bias for hemoglobin concentration measurements: −3 [−10; 5] g/L in the 37-bed ICU.ConclusionWe clearly demonstrate that an identical analyzer can provide results of varying quality depending on the local constraints of the ICUs. We demonstrate that quality management focused on the preanalytical process and performed by the partners involved in the POCT can overcome these issues.

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

“…There are some notable limitations of this study. Firstly, our study did not explore the pre‐analytical process of using POCT machine which would impact on the quality of results as previously reported . The analysis of factors, such as plasma proteins, leukocyte count, arterial vs venous sample, sample collection, and handling, may help explain the observed biases and limits of agreement.…”

“…Firstly, our study did not explore the pre-analytical process of using POCT machine which would impact on the quality of results as previously reported. 24 The analysis of factors, such as plasma proteins, leukocyte count, arterial vs venous sample, sample collection, and handling, may help explain the observed biases and limits of agreement. Another limitation which is present in several other studies is unavoidable due to retrospective design, and due to pragmatic reasons, is the time difference between the sampling for the two tests.…”

Comparability of Point-of-Care versus Central Laboratory Hemoglobin Determination in Emergency Patients at a Supra-Maximal Care Hospital

“…Also, pre-analysis plays a decisive role not only in the measurement of Hb, but of all parameters. Studies based in ICUs have identified a sound quality management as an essential component in order to achieve valid results [16]. Time to analysis is another critical factor.…”

Pre-analytical error for three point of care venous blood testing platforms in acute ambulatory settings: A mixed methods service evaluation

“…More generally, our estimate of error rates only considers test attempts that provoked an error message from the POCT device. It was not possible to assess whether an incorrectly filled cartridge or poor quality sample might have given an inaccurate and therefore clinically misleading test result if the device did not initiate an error message, and this may be affected by the site of sampling or the timing when the test was performed [28]. Additionally, failed attempts in which the operator discarded a cartridge without inserting it into the machine would not be recorded, and this may have introduced some inaccuracy into our estimate of error rates.…”