Could the Intra-Laboratory Inter-Identical-Instrument Bias Compromise the Interpretation of the Absolute High-Sensitive Troponin Delta Around the 99th Percentile Upper Reference Limit?

Aim of study: To measure high-sensitive troponin (Access hsTnI) interidentical- instrument bias (DxI800 Beckman Coulter) in order to understand if it can compromise interpretation of delta value for rapid algorithms 0/1-0/3 hours.Materials methods: One hundred fifty-nine lithium/heparin plasma samples were processed sequentially on three DxI800 (DxI1, DxI2, DxI3). results given by three instruments were analyzed as followed: DxI1 vs. DxI2, DxI1 vs. DxI3, DxI2 vs. DxI3. Statistical analysis was done using Passing-Bablok regression, Bland-Altman test, Cohen’s Kappa statistic.Results: PB regression did not show any significant deviation from linearity and no proportional nor constant differences were observed among instruments. Moreover, mean bias, even though among three instruments the lowest 95%CI lower limit was -3.75 highest 95%CI upper limit was 3.92 ng/L, was within acceptance limits (all resultsu003creference change value). The concordance between each couple of instruments was mostly strong.Conclusion: Our data suggest inter-identical-instrument bias needs to be considered before evaluating clinical diagnostic accuracy of one absolute delta with respect to another, in order to define minimum delta that laboratory can guarantee to clinicians.