False decrease of high-sensitivity cardiac troponin T assay in pneumatic tube system samples

Background: The pneumatic tube system (PTS) is widely established in clinical laboratories. We aimed to evaluate the impacts of PTS on high-sensitivity cardiac troponin T (hs-cTnT) assays. Methods: The hemolysis distribution of hs-cTnT PTS specimens from emergency department (ED) were determined by hemolysis index (HI). Grouped samples from 15 healthy volunteers were delivered to the laboratory via manual delivery (MD) or PTS. Interference studies were conducted to access the influence of different hemolysis degrees on hs-cTnT assays. Results: 7.26% PTS specimens from ED were hemolyzed in clinic. Compared with MD samples, we found highly elevated free plasma hemoglobin (Hb) in PTS samples. Hs-cTnT was interfered negatively with free Hb (R = -0.625, P <.001), and it was also validated in interference studies (R >= -0.820, all P <= .001). Clinically significant bias occurred in each hs-cTnT concentration at 100 mg/di free Hb (Bias >= -13.85%, all P <.05). Moreover, bias of hs-cTnT assays at 50 mg/dl free Hb was approaching 10%, especially at 30 ng/l hs-cTnT concentration (Bias :-11.72%, P < .001). Conclusions: PTS could increase the frequency of specimen hemolysis which might cause false decrease in hs-cTnT assays. Hence, clinicians should be aware of the increased measurement bias in hs-cTnT from hemolyzed PTS samples with free Hb >= 50 mg/dl.