Preanalytical error: Improper gel barrier formation in a serum separator tube despite appropriate centrifugation condition

Abstract

Abstract The clinical laboratory is a significant component of patient care, as laboratory data inform 60–70% of critical decisions related to admission, discharge, and medication administration. However, missteps occurring in specimen collection, transport and storage (preanalytical phase); testing (analytical phase); and reporting (post-analytical phase) may produce errors that affect patient safety and unnecessarily burden hospital budgets. Preanalytical errors may result from the devices used for blood collection. These devices have complex interactions with blood and can alter the composition of the serum and plasma fractions in ways that are not always fully appreciated by health care professionals. In some cases, such alterations can adversely affect laboratory test results. For instance, components of blood collection tubes (BCTs), including stoppers, stopper lubricants, tube walls, surfactants, clot activators, tube additives, and separator gels, may cause inaccuracies in test results by changing the chemical composition of the blood sample. Examples in the literature include BCTs leaching constituents into blood, adsorbing elements, or interacting with protein and cellular components. Additives and chemicals associated with BCT manufacturing can also significantly alter analyte stability in blood specimens. Here, we describe the case of a 14-month-old female with infectious mediastinitis and mild anemia who underwent a CT scan with contrast medium before blood collection. She has an increased INR and receives periodic boluses of diluted papaverine. After blood collection and subsequent tube centrifugation, abnormal gel migration was observed in one serum separator tube (SST™), with gel trapped at the bottom of the tube below the clot. A review of the preanalytical system software confirmed that the SSTs from this patient were placed on the preanalytical line and centrifuged at 1300g for 10 min. We performed several tests to determine the cause of the displaced gel at the bottom of the SSTs after centrifugation. Although not recommended by the tube manufacturer, recentrifugation (1300g for 10 min) of the problematic SSTs resulted in proper gel separation. Thus, we hypothesized that the gel in the SSTs was defective and required additional centrifugation to move the gel upward in the tube to be positioned between the serum and cellular constituents. Abnormal gel movement to the top of the serum or plasma layer in SSTs or plasma separator tubes during centrifugation has been reported. This phenomenon has been attributed to an increased specific gravity of the serum or plasma, which in turn may be caused by hyperproteinemia or the presence of contrast medium used in diagnostic imaging. However, to our knowledge, ours is the first reported case of centrifuged gel remaining at the bottom of the SST. The finding of the gel at the bottom of an SST after centrifugation is important to laboratorians. Many clinical laboratories use preanalytical lines to centrifuge and transport tubes directly to chemistry instruments for analysis. These tubes are typically not visually inspected before the specimen is tested, hence improper gel separation in bottom of the tube. Partial or complete obstruction of the sample probes with cellular constituents may produce erroneous test results and increase turnaround time and costs, ultimately impacting patient care. Thus, this case may serve to remind clinical laboratorians that BCT failures are a source of preanalytical errors, and investigation of the integrity of BCTs is an essential part of trouble-shooting erroneous test results.