Clinical laboratories frequently either introduce new tests or update those in current use. Rarely, however, updates for existing assays yield significant differences in both numerical values and in decision limits. This poses a challenge where established traditional validation and correlation studies cannot be applied and the only way to apply clinical correlation involving review of patients’ clinical findings and outcomes. This is the case for the high sensitivity troponin T (hs-TnT) approved by the FDA. In addition to the assay’s much improved sensitivity, the reporting units, reference intervals and critical limits are markedly different from the conventional Troponin T assays. Furthermore, current ‘in-use’ acute myocardial infarction (AMI) rule out protocol requires serial samples and monitoring for up to 6 hours and it is not known if adopting hs-TnT will impact the protocol.
Joining forces with clinical colleagues from Cardiology, Emergency Medicine, and Internal Medicine Hospital Practice allowed the validation as well as implementation of the high sensitivity Troponin T assay.
The current rule-out protocol in patients presenting with chest pain and suspected of acute coronary syndrome was to measure troponin levels on admission and at 3 and 6 hours post baseline levels. In anticipation of possible changes to the rule-out protocol, following literature review, emergency department nursing and medical staff were requested to order an additional troponin sample at one hour following the baseline sample.
Laboratory technical validation of the hs-TnT 5th generation assay such as; accuracy, linearity, precision, were performed following assay set up on the instrument. Samples received during clinical management were assayed for troponin T and only those by the conventional methodology reported as part of routine care. Troponin levels obtained by both assays were reviewed for clinical correlation and outcomes by cardiology experts. A one hour and three hour levels rule-out protocols were developed1. The team facilitated the training of laboratory personnel, nursing and medical staff with regard to the new protocol and new assay values and limits. The generated comparative data that the clinical teams can understand was used. A successful implementation was achieved. This implementation process reinforced the central role of the laboratory to patient care and outcome. Relationships were strengthened. It is clear that where most assays can be validated within the clinical laboratory in isolation, few require extensive involvement and collaborative efforts as shown above. We encourage laboratory colleagues to interact with clinical staff when implementing the new hs-TnT assay.
- Rebecca Vigen PK, Fernabelle Fernandez, Amy Yu, Bryan Bertulfo, Ibrahim A. Hashim, Kyle Molberg, Deborah B. Diercks, Jeffery C. Metzger, Jose Soto, Dergham Alzubaidy, Lorie Thibodeaux, Jose A. Joglar, James A. de Lemos, Sandeep R. Das. Evaluation of a novel rule-out myocardial infarction protocol incorporating high sensitivity troponin T in a US Hospital. Circulation 2018;138.