Specimen recentrifugation and elevated troponin I levels.

OBJECTIVE To compare troponin I levels in plasma before and after specimen recentrifugation. METHODS Over a period of 24 consecutive days, we recentrifuged 189 plasma specimens in which the troponin I level was higher than the positivity cut off (60 ng/L) and then remeasured the troponin I. RESULTS Two-tailed Wilcoxon matched-pairs test results identified a statistically significant difference between troponin I concentrations before and after recentrifugation (P <.01). For 94 specimens close to the cut-off value (below the 50th percentile among the overall sample of 189 specimens), Passing-Bablok regression analysis showed a median reduction of 10 ng/L (95% confidence interval, -37.5 ng/L - -10.0 ng/L) in the concentrations of troponin I after recentrifugation. CONCLUSION Specimen recentrifugation is followed by a reduction in troponin I concentrations in specimens with elevated cardiac troponin I, posing a risk for misclassification of patients. Moreover, this practice gives rise to unnecessary prolongation of turnaround time.