A Rational Adoption of the High Sensitive Assay for Cardiac Troponin I in Diagnostic Routine

Figure 1. Total imprecision (CV%) for the TnI and hsTnI assays at four levels of internal controls assayed for the duration of the study. The 20 ng/mL pool has not been assayed by TnI as it is below the LoQ for this assay. IQC = internal quality control.

Figure 2. Rates of detection for cardiac troponin I by TnI (a) and hsTnI (b) assays by gender and age classes.

Figure 3. Bland–Altman difference plot (absolute values) between TnI and hsTnI in the range between 44 and 600 ng/L. One outlier (arrow) was observed.

Figure 4. Receiver operating characteristics (ROC) curves for hsTnI according to an increase at 3 and 6 hours compared to baseline.

Figure 5. Clinical case 1. Increase of cardiac troponin I by the TnI and hsTnI assay in a male patient eventually diagnosed with NSTEMI. The imprecision for the results obtained at T3 was established by repeating each assay four times. Percentages in red represent the increase by hsTnI compared to baseline. CV = coefficient of variation. Red line: threshold for hsTnI; blue line: threshold for TnI.

Figure 6. These patients (female, 82 years, acute hearth failure) would have been effectively ruled out for an acute coronary syndrome by the hsTnI assay after 3 hours, according to the ESC guidelines [2], but not by TnI. Percentages in red represent the increase compared to baseline. Red line: threshold for hsTnI; blue line: threshold for TnI.

Figure 7. Clinical case 3. This 91-year-old female patient was one of the two “false positives” by hsTnI. The increase of TnI after 3 hours (bold red) was significant by both assays, but values above the diagnostic threshold (gender-specific 99th percentile) could be recorded only by hsTnI. Red line: threshold for hsTnI; blue line: threshold for TnI.

Figure 8. Accelerated (0 and 1 hour) testing algorithm from the ESC 2015 guidelines. Values refer to the Architect hsTnI assay results.

Figure 9. Mortality due to acute coronary syndrome (a) and all-cause mortality (b) after 18 months from enrollment in the study according to baseline hsTnI values on the 202 patients enrolled at the Civil Hospital in Sondrio.

Figure 10. Diagnostic algorithm for patients with suspected NSTEMI adopted at both study sites after the experimental phase with hsTnI. The algorithm has been derived from the ESC 2015 Guidelines [3] and takes in account also the time from the onset of symptoms.