Why the study?
Does a simplified spreadsheet method reliably derive INR from the PT/INR Line without complex linear regression?
Does a simplified spreadsheet method reliably derive INR from the PT/INR Line without complex linear regression?
A simplified spreadsheet method allows for easy derivation of INR from the PT/INR Line without the need for complex linear regression or local calibration.
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Offers low-complexity INR derivation for labs; leaves open prospective validation before routine use.
BACKGROUND: The prothrombin time/international normalised ratio (PT/INR) Line method to derive INR, based on only five European Concerted Action on Anticoagulation (ECAA) certified plasmas, is shown to be reliable in previous ECAA studies. A simpler method not requiring linear regression calculation would be an advantage. METHOD: After determining the local PT/INR Line, local INRs have been obtained using a readily available spreadsheet on the internet which laboratories can use without performing any additional calculations. RESULTS: Examples of INR derivation have been obtained from results at 16 centres using a range of local coagulometers with human thromboplastin international reference preparations (IRPs). The procedure does not require manual PT testing, local international sensitivity index calibration, availability of thromboplastin IRPs or local mean normal prothrombin time. CONCLUSIONS: From the PT/INR Line, INR values for local PT results are easily obtained using an Excel spreadsheet from our website (http://www.anticoagulants.co.uk/) which does not require the complex linear regression analysis to derive INR.
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Poller et al. (2011) studied this question.
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