High-sensitivity troponin T(hs-cTnT) testing plays a critical role in determining if someone has had a heart attack, and it often is deployed in the emergency department. But hemolysis, a breakdown of red blood cells, presents a common problem for hs-cTnT testing. Hemolysis can lower the concentration of troponin T in blood collection tubes, which can affect the accuracy and turnaround time of hs-cTnT testing. This can significantly delay patient care by leading to false negatives that indicate that someone hasn’t had a heart attack when they actually have.
The prevalence of hemolytic specimens can be as high as 3.3% of all routine samples, accounting for 40%−70% of all unsuitable samples identified, previous research shows (Oman Med J 2019; doi: 10.5001/omj.2019.19).
New research has been done to identify when and how hemolysis occurs during sample collection in the emergency department, which in turn could help labs to find solutions to this serious problem.
Hind Malaeb, PhD, a postdoctoral scholar at the University of Kentucky School of Medicine, led a 2023 study that addresses this issue. The study, published in Clinica Chimica Acta, shows how switching the type of tube used for blood collection reduces hemolysis and thus preserves the integrity and efficacy of hs-cTnT testing (Clin Chim Acta 2023; doi: 10.1016/j.cca.2023.117630).
Malaeb recently spoke to Clinical Laboratory News about that work, the importance of getting accurate results from hs-cTnT testing, what commonly spurs hemolysis, how new but uncommon types of tubes can help, and what changes healthcare institutions should make to ensure that hs-cTnT will be most effective in the sometimes-chaotic emergency department environment.
What are the primary sources of hemolysis during sample collection in the emergency department and how do they impact hs-cTnT testing accuracy?
We initiated this investigation through structured discussions with emergency department nursing staff to identify potential preanalytical sources of hemolysis.
One major contributing factor is the blood collection method. In patients with difficult venous access, such as pediatric, elderly, or frequently hospitalized individuals, smaller gauge needles are often used. However, the narrower gauge increases shear stress on erythrocytes, thereby elevating the risk of hemolysis.
Venipuncture technique also plays a critical role. Using syringes or “straight stick” draws can generate higher negative pressure, predisposing red blood cells to mechanical stress and rupture. Furthermore, proper tube handling is essential. Following collection, tubes should be gently inverted to ensure adequate mixing of blood with additives. Tubes should not be shaken vigorously, which can compromise cell integrity.
One of the other important things to consider when it comes to additives is underfilling or overfilling the tubes. Tubes are designed with specific filling margin marks to guide proper tube filling. Underfilling tubes alters the appropriate blood to additive ratio, potentially leading to cellular lysis and analytical interference.
Finally, specimen transport method influences hemolytic risk. Underfilled tubes subjected to pneumatic tube transport experience greater mechanical stress and pressure changes, significantly increasing the likelihood of hemolysis compared to specimens manually delivered to the laboratory.
Why is this a problem?
Hemolysis can falsely decrease hs-cTnT concentrations, increasing the risk of false-negative results and potential misclassification of patients with myocardial injury.
Serial hs-cTnT testing is routinely performed, typically at baseline and again after 2 hours. Clinical interpretation relies on the delta change between these sequential measurements to differentiate acute myocardial injury from chronic elevation. When one or more specimens are hemolyzed, the resulting troponin values become unreliable, compromising delta calculations and invalidating the diagnostic algorithm.
How effective are rapid serum tubes (RST) at mitigating hemolysis-related delays and improving the reliability of hs-cTnT testing in the emergency department?
As the name suggests, RST contain a specialized clot activator that significantly reduces clotting time compared to standard serum separation tubes (SST). While SST typically require 20-30 minutes for clot formation, RST achieve complete clotting in approximately 5 minutes after collection with inversion to ensure proper additive mixing.
The tubes also contain a gel barrier that effectively separates serum from cellular components upon centrifugation. Beyond improving turnaround time, RST offer an additional advantage in minimizing hemolysis risk during transport. The formed clot creates a stable mesh that secures cellular elements, reducing mechanical stress from agitation or pneumatic transport. This protective structure provides a more stable microenvironment for red blood cells compared to plasma serum tubes (PST). This finding was demonstrated by our 2023 study published in
Clin Chem Acta and by an earlier study published in the
Journal of Clinical Pathology (
J Clin Pathol 2022; doi: 10.1136/jclinpath-2021-208126).
How common are RST compared to PST?
Despite their advantages, RST remain less commonly used than PST. This is partly due to their relatively recent introduction into clinical practice; however, a primary barrier to widespread implementation is their higher cost compared to PST.
What strategies can healthcare institutions use to minimize the risk of false positives when using PST?
When using PST, it is advisable to employ a larger-gauge needle whenever feasible to minimize shear stress on erythrocytes during venipuncture, thereby reducing the risk of hemolysis.
Blood collection using evacuated tube systems is also recommended, as these systems maintain a consistent negative pressure that allows controlled blood flow into the tube, minimizing mechanical trauma compared to direct syringe aspiration.
Furthermore, venipunctures should be preferred over IV blood draws. Specimen collection from IV sites increases the likelihood of hemolysis, in addition to introducing potential preanalytical errors such as dilution or contamination with IV fluids.
Jen A. Miller is a freelance journalist who lives in Audubon, New Jersey. +Bluesky: @byjenamiller.bsky.social
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