A laboratory specimen is a biological sample—such as blood, urine, or tissue—collected from a patient for analysis to aid in diagnosis or monitor treatment. Specimen rejection occurs when the laboratory deems a collected sample unsuitable for testing because it fails to meet strict quality or safety criteria. When a sample is rejected, no result can be produced, which interrupts the diagnostic process and signals a breakdown in healthcare quality. Maintaining the integrity of these samples is a fundamental requirement for generating accurate and reliable test results for patient care.
Where Errors Most Frequently Originate
The majority of errors leading to specimen rejection originate in the pre-analytical phase of the testing process. This phase encompasses everything that happens to the sample before it reaches the analytical instruments, including test ordering, collection, handling, and transport.
Studies consistently show that the pre-analytical phase is the source of approximately 60% to 70% of all laboratory errors, far exceeding those from the testing or reporting phases. Because collection involves many different personnel—from phlebotomists to nurses and transport staff—it introduces numerous points where mistakes can occur. The quality of the final test result depends heavily on the standardization of these initial procedures.
Common Causes Related to Sample Integrity
One of the most frequent reasons for rejection is hemolysis, which is the rupture of red blood cells (RBCs) in the sample. This physical damage releases intracellular components, such as potassium and certain enzymes, into the fluid portion of the blood (plasma or serum). The presence of these components can chemically interfere with many laboratory assays, leading to falsely elevated or depressed results that are clinically misleading.
Another common issue is Quantity Not Sufficient, often abbreviated as QNS, where the volume of the sample collected is inadequate for the ordered test. Certain tubes contain specific anticoagulants, and the ratio of blood to the additive must be precise to ensure the test runs correctly. If the tube is underfilled, the concentration of the additive is too high, which can interfere with the chemistry or coagulation testing process.
For tests requiring whole blood or plasma, the presence of a clot in a tube that contains an anticoagulant will result in rejection. Anticoagulants, such as EDTA or heparin, are designed to prevent the blood from clotting, so the presence of a clot indicates a failure to properly mix the sample immediately after collection. This clotting consumes platelets and other factors, making the sample unusable for accurate hematology or coagulation studies.
The use of the wrong collection container or tube type is also a major source of integrity-related rejection. Collection tubes are color-coded to indicate the specific additive they contain, which determines the type of test they can be used for. For instance, a blood glucose test requires a tube with an antiglycolytic agent to stabilize the sugar, and a sample collected in the wrong tube may not have the necessary stabilizing agent, rendering the result invalid.
Common Causes Related to Identification and Procedural Compliance
Errors in patient identification and labeling are mandatory rejection criteria driven by patient safety regulations. Unlabeled or mislabeled specimens are rejected immediately because testing them introduces the risk of reporting a result to the wrong patient. Most laboratories require two unique patient identifiers, such as name and medical record number, to be present and accurate on both the sample and the test order.
Procedural compliance failures related to improper transport and storage frequently compromise sample quality. Many tests require the sample to be kept at a specific temperature, such as refrigerated or protected from light, to maintain the stability of the analytes. Delays in transport that cause the sample’s stability time to be exceeded can lead to the degradation of sensitive compounds, such as certain hormones or blood gases, making the final result unreliable.
The collection devices themselves can sometimes be the source of rejection if they are expired. Collection tubes rely on a vacuum to draw the correct volume of blood, and the integrity of the vacuum and the chemical additives can degrade over time. Using an expired tube can lead to an underfilled sample or a failure of the additive to prevent clotting, which results in the laboratory rejecting the specimen.
Contamination of the sample also necessitates rejection to prevent erroneous results. For example, drawing blood from a vein above an active intravenous (IV) line can dilute the sample with the IV fluid, artificially lowering or raising the concentration of substances being measured. External contaminants, such as powder from gloves or residual antiseptic solution, can also interfere with the analytical process, making the sample unusable.
The Impact of Specimen Rejection
Delay in Diagnosis and Treatment
The most immediate consequence of specimen rejection is a significant delay in diagnosis and subsequent treatment for the patient. The time required to notify the care team, recollect the sample, transport it, and re-run the analysis can add an average of 65 to over 100 minutes to the total turnaround time. This delay is particularly concerning for time-sensitive tests where rapid results are necessary for emergency medical decisions.
Patient Discomfort and Trust
Specimen rejection leads to increased discomfort and inconvenience for the patient, typically requiring a repeat collection procedure. Repeated phlebotomy can cause physical discomfort and carries a small risk of complications like hematoma formation or blood loss, especially in fragile patients. Furthermore, the necessity of repeat procedures and delayed results can erode patient confidence in the quality of care provided. Consistent pre-analytical errors lead to patient dissatisfaction and a loss of trust.
Increased Costs and Resource Waste
From a systemic perspective, rejection increases overall healthcare costs by wasting resources and staff time. Every rejected sample represents a wasted collection kit, staff time for collection and processing, and the cost of the repeat test. Models suggest that the consequences of rejected specimens can add several hundred dollars to the cost of care per hospital patient annually. Monitoring and reducing rejection rates is a continuous quality improvement measure affecting both clinical outcomes and patient experience.