Title:Resolution of early reaction errors (ERE) in haemostasis testing at Wellington SCL

Author:M Hill, R O'Toole, C Kendrick.

Abstract:Background: At the Southern Community Laboratories (SCL) Wellington laboratory, the Sysmex CS2100i analyser (Siemens) is responsible for the testing of all samples submitted for haemostasis evaluation. One of the limitations of this equipment is a tendency to produce invalid international normalised ratio (INR) and activated partial thromboplastin (APTT) tests on some samples due to early reaction errors (ERE). This requires additional sample processing and sometimes a patient re-bleed. The STart Max (Stago) semi-automated benchtop analyser showed promise as a suitable alternative method since it used mechanical clot detection, rather than an optical method, and potentially the ability to eliminate problematic ERE’s. This in turn might reduce delays in reporting results and sample recollection.
Methods: The STart Max analyser underwent validation using the methodology outlined in the IANZ specific criteria for accreditation (Medical Testing 7). Validation included the development of reference ranges for the prothrombin time/international normalised ratio (PT/INR) and the APTT. Accuracy and precision characteristics were assessed using patient samples, external quality control samples and samples that had previously produced ERE results on the CS2100i. All results were statistically evaluated using Analyse-it software.
Results: Results for the PT/INR and the APTT showed good correlation with the Sysmex CS2100i analyser (r-value >0.95) and external QC samples. However, for the APTT, there was a significant difference between the two methods (1-11 secs). The reference ranges for the STart Max were found to be similar to those in use for the INR on the Sysmex CS2100i. For APTT, the reference ranges did not show uniform similarity between the two methods. Tests for precision produced a coefficient of variation (CV) of < 4% in all tests except for the elevated range of the APTT where this was 4.96%. The STart Max analyser was able to generate reportable results for all samples that generated ERE results on the Sysmex CS2100i analyser.
Conclusions: The generation of patient sample results affected by unresolvable ERE results with the Sysmex CS2100i analyser highlighted the need for an alternative method in the laboratory. This study has shown that the STart Max analyser produced comparable results to those from the CS2100i. With the exception of the APTT, a regional biological reference range can be used for reporting results from the STart Max analyser. The STart Max analyser also showed that it was able to generate reportable APTT results on samples rejected for ERE using the Sysmex CS2100i analyser. The results of this study has allowed the validation of the STart Max analyser for use at Wellington SCL.
Key words: haemostasis, international normalised ratio, activated partial thromboplastin, early reaction errors.
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