The majority of all diagnostic labs will turn back some of the samples that they receive. Some of the reasons for turning back include: the tube has clotted, the label on the sample does not correspond with the request form, or the amount of sample is insufficient for the ordered test. Turning back samples is a standard practice and is required to maintain the quality control standards of the laboratory; however, each time a sample is turned back, it results in a re-collection, a delay in reporting, waste of materials and inconvenience to the patient.
The positive side is that the majority of sample rejections occur in the pre-analytical phase – the steps taken prior to analyzing the sample – and these steps are easily improved through the implementation of clear procedures, training and effective communication/coordination. In this guide you will learn how to determine your sample rejection rate, understand why samples are commonly rejected, and ultimately how to lower your sample rejection rate using a logical and evidence-based approach.
What Is a Sample Rejection Rate?
A Sample Rejection Rate is the percentage of samples that a laboratory has received and was unable to test, or were unusable for testing due to not meeting the laboratories' acceptance criteria. Simply put, it indicates what portion of the total samples received had to be either rejected or recollected.
Laboratories monitor laboratory sample rejection for three reasons:
- Safety of patient and accuracy of test outcome. Using a sample that is not appropriate may lead to false test outcomes.
- Operational efficiency. Recollections increase the amount of work to be done, slow down how fast you can turn around orders, and drive up cost.
- Quality improvement. Rejection data identifies where there are weaknesses in the process (e.g., collection, labeling, transportation, or processing).
A rejection of a sample does not imply that someone has been negligent. There are many reasons why a sample may be rejected, including the presence of an difficult to access vein, or a patient who suffers from a disease which makes obtaining a sample difficult. These factors cannot be controlled. The objective of this program is not to eliminate all rejections, but to reduce those which could have been avoided.
How to Calculate Sample Rejection Rate
The standard formula is:
Sample rejection rates are calculated using the following formula: Sample Rejection Rate (%) = (Number of samples rejected / total number of samples submitted) x 100.
An example for the sake of explanation: A laboratory processes 4,000 samples during a month and rejects 60 of those. Therefore, the rejection rate for that laboratory would be (60/4,000) * 100 = 1.5%.
Define your definitions prior to beginning measurement. Choose if you will count the sample tubes or samples themselves, whether recollection is considered a new sample, and if you consider partial rejection (one tube out of many) a part of the calculation. Ensure that you maintain the same definition of what is being measured throughout the trend analysis, so that the trends developed have relevance. There is no one specific target rate which can be applied to all laboratories because each laboratory has a different case mix, collection model and test menu; therefore, prior to comparing your results with those of other laboratories, analyze your own results over time.
Common Reasons for Sample Rejection
Sample rejection reasons and other errors related to collecting samples can usually be broken down into a few main categories. It is important to remember that the specific guidelines for accepting or rejecting a sample depend on several factors, including the type of sample being collected, the required testing for the sample, what the manufacturer specifies in regards to sampling, and your facility's validated standard operating procedures (SOPs).
Hemolysed blood samples
When red blood cells rupture and release their components into the blood stream (i.e. serum or plasma), this is referred to as hemolysis. This may cause an interference with some testing procedures. There are many reasons why this occurs including; a difficult or long drawing procedure, using a small gauge needle/catheter, forcibly transferring blood from a syringe to a tube, vigorously shaking the tube after collection, waiting too long to separate the blood from the cells and/or transporting the blood under inappropriate conditions. Depending upon the type of test being performed and what is outlined within your standard operating procedures (SOP), will determine whether you reject the hemolyzed sample or report it with a statement indicating that it has been affected by hemolysis.
Clotted blood samples
A clot can form in an anticoagulated tube (like a complete blood count) if it has not been mixed gently and immediately after being drawn; if it took a long time to draw; or if the correct type of tube was not used. A clot may alter cell counts and clog analyzers.
A clot can form in an anticoagulated tube (like a complete blood count) if it has not been mixed gently and immediately after being drawn; if it took a long time to draw; or if the correct type of tube was not used. A clot may alter cell counts and clog analyzers.
Insufficient sample volume
A tube that is underfilled will result in an incorrect ratio of blood to additive and may not contain enough sample for all of the tests ordered. Different tests require varying amounts of sample, therefore follow the directions on the tube and test.
Incorrect collection tubes
Using an incorrect tube, anticoagulant, or container for a specific test, or drawing samples in an inappropriate sequence (order of draw), may result in inaccurate test results. Laboratories must have a clearly defined reference guide for matching each test with its correct collection tube at every sample collection site.
Improper sample labelling
Because of the serious consequences of not being able to identify a sample, there is no greater danger to safety than missing, mislabeled, unreadable or detached labels. When a sample cannot be positively identified with the correct patient, it cannot be safely used. In addition, many times the error in labeling a sample or other identification problems will require that a new sample be collected even if the original sample would have been adequate.
How to Reduce Sample Rejection Rates in Diagnostic Laboratories
The sample rejection prevention will work best if you focus on improving the process rather than trying to improve individual performance. The following are the best ways to ensure your sample rejection prevention is successful.
1.Standardise sample collection procedures
All sites must use the same sampling best practices. This includes the use of written, up-to-date SOPs for patient preparation, selection of tubes, order of draws, mixing of specimens, volume of specimens, identification/labeling of specimens and storage of specimens prior to shipping. In addition, there should be a visible reference chart displaying this information near all points where samples are collected, i.e., at each collection center and inside each home-collection kit.
2.Train phlebotomists and laboratory staff
Provide initial training for new employees prior to their independent work, and provide ongoing education for all employees. Address employee techniques, patient interactions, tube management, and the rationale behind each procedure. When employees are aware of the importance of such procedures as gentle mixing and proper tube filling, they will make better clinical decisions while working with patients. Maintain documentation of all employee training and utilize rejection data to focus on specific educational areas.
3.Improve patient identification
To reduce the use of handwritten notes, print labels using information entered into the registration record. Verify that the identification of the patient has been confirmed with the patient or their caregiver, and verify that the identification matches the identification listed in the request.
4.Use the correct tubes and volumes
Make sure you have the proper tubes on hand, that they are labeled correctly with their expiration date, and that you are filling them to the line indicated when necessary. Use the manufacturer's directions for each tube and test.
5.Label correctly and use barcode identification
The label goes on the front of the patient, at the time of collection, never prior to that point. Using a barcode to track samples helps eliminate error in transcribing data and allows for tracking of every transaction. The goal is a uniform, consistent identification throughout the process (from registering the sample to reporting results).
6.Maintain proper storage and transport conditions
Set forth the temperature, time restrictions and packaging requirements for all sample types; provide proper shipping containers; document when samples are sent and received; train sample collectors and couriers regarding how to handle samples. When the laboratory establishes time constraints, use those established by validated methods and the manufacturer's recommendations.
7.Establish clear acceptance and rejection criteria
Create a written list of standards for each type of sample being collected. Share this document with the people who collect these samples so that they are aware of the specifications that the lab has for each type of sample. If the collection personnel understand which types of samples are acceptable to the laboratory and which ones are not acceptable, then they can resolve any discrepancies prior to sending the sample off to the lab. Review the standard list regularly with your quality manager and pathologist.
8.Improve coordination between collection centres and the laboratory
Provide feedback on rejections to collection centers quickly, along with the cause of the rejection and proposed solution. Establish collection times, cutoff dates, and point-of-contact for questions. Share rejection statistics on a monthly basis with all locations.
9.Monitor sample rejection trends
Monitor how many samples are rejected based on sample type, where the sample was collected, when it was collected (shift), who collected it (staff group), and why the sample was rejected. Identify if there are trends, like an increase in hemolysis at a particular facility or an increase in labeling errors following a change in staffing.
10.Investigate recurring errors and act
In order to address chronic issues, determine the underlying source: is it due to training, equipment, tubes, workload, transportation, or an ill-defined SOP? Document the corrective measures, identify the individual responsible for taking those measures, and then assess if there has been improvement in the frequency of occurrence.
11.Use laboratory management software for tracking and visibility
The following section will discuss how digital systems can assist with most of the processes listed previously.
Role of Laboratory Management Software in Sample Rejection Prevention
The Laboratory Information System (LIS) or Laboratory Management Software cannot create better samples, however, it makes following good procedures easier and finding problems much more evident. Here are some of the most useful features that the LIS/LIMS provide:
- Patient/Sample Identification: To create unique IDs/labels using the registration record, thereby reducing human error in writing.
- Barcode-based sample tracking: scan at collection, dispatch, and receipt to record each change of custody.
- Sample Status Visibility: Shows the status of samples that have been collected, are in-transit, have been received, rejected, or are being tested.
- Collection and processing record: capture collection time, collector, receipt time and condition.
- The record of each rejection: to record all the consistent reasons for each rejection so that there is an opportunity to analyze them.
- Workflow Coordination: Assisting collection centers and the laboratory in utilizing the same data.
- Operation Record Management: create an audit trail that can be searched for review and/or audit purposes.
One such example of a laboratory management platform which integrates patient/sample management; test/report management; billing and inventory into a single connected system is called Marglabz. Laboratories who are looking for the ability to monitor the status of samples; records of rejected samples; and reporting within one application will find this type of integrated approach makes the monitoring discussed throughout this article simpler. Like any software available today, take time to view a demo of Marglabz to ensure the features align with your current laboratory workflow. Additionally, please keep in mind that Marglabz is designed to assist laboratory personnel and procedures and not replace them.
Key Metrics to Monitor Sample Rejection
| Metric | What It Tells You |
|---|---|
| Overall sample rejection rate | General trend in collection and handling quality |
| Rejection by sample type | Which specimens are most affected, such as blood, urine or swabs |
| Rejection by collection centre | Sites that may need training or support |
| Rejection by reason | Whether hemolysis, volume, labelling or transport dominates |
| Repeat collection frequency | Burden on patients and staff |
| Trend over time | Whether improvements are working |
An example of how to use these figures hypothetically would be if a laboratory that rejected 60 specimens during one month determined that 24 of those rejections were because the specimen was hemolyzed, 14 of those rejections were due to insufficient specimen volume, 10 of those rejections were due to labeling errors, 7 of those rejections were due to the incorrect tube being used and 5 of those rejections were due to clotting. The primary focus of this laboratory should be to assess the methods of specimen collection and subsequent handling which led to the hemolysis and then assess the specimen collection and labeling process. This hypothetical data is provided to illustrate the process described above and does not represent actual benchmark data.
Review these monthly numbers with your team. Treat them like a quality control measure, not like an opportunity to point fingers at specific people.
Common Mistakes Laboratories Should Avoid
- Lack of adequate employee training. Utilizing "on-the-job" learning, but without periodic reviews or tests to assess employees' knowledge.
- Inconsistent labeling. Different organizations using different techniques for labeling, or labeling the sample prior to collection.
- Lack of coordination in transportation. lack of agreement regarding schedules, packaging, and temperature regulations.
- Unclear rejection criteria. Staff guessing what the lab will accept.
- Not reviewing rejection data. Recording rejections but never analysing them.
- Individuals blamed. Causes of systems ignored (e.g. workload, equipment, unclear SOPs)
- No communication after rejection. No clear explanation given to the patient or collection center as to why they were rejected and what will be done next to recollected.
Practical Sample Rejection Prevention Checklist
Use this checklist in daily operations and adapt it to your SOPs.
Before collection
- Patient identity confirmed with two identifiers
- Test requirements, fasting or timing conditions checked
- Correct, in-date tubes and containers ready
- Request details match the registration record
During collection
- Correct technique and order of draw followed
- Tubes filled to the required volume
- Tubes mixed gently as instructed
- Label printed from the record and applied in front of the patient
After collection and in transit
- Samples stored at the required temperature
- Dispatch list prepared and times recorded
- Packaging suitable for the sample type
- Pickup and cut-off times respected
At receipt in the laboratory
- Samples checked against the dispatch list
- Identity, tube type, volume and condition verified against criteria
- Rejection reason recorded consistently when needed
- Collection centre or patient informed promptly
Ongoing
- Rejection data reviewed monthly by site, type and reason
- Recurring causes investigated and corrective actions recorded
- Training updated based on findings
Conclusion
Reducing sample rejection rates comes from both discipline and awareness. You can achieve this through having standard processes, training staff on those processes, accurately identifying patients, selecting the correct size and volume of tubes for each sample, properly handling and transporting samples, and conducting regular reviews of the results. Because there are no specific standards for what constitutes an acceptable sample, and therefore no set target for a "successful" sample rejection rate, the focus should be on reducing the number of samples rejected due to errors, which will ultimately result in faster and more accurate results.
Measure the rejection rate from your laboratory and determine why it is happening. Then work on reducing the single largest cause of the rejection rate. Reevaluate in several weeks. Marglabz a laboratory management software program, can help you track sample status and rejection history. However, there are no substitutes for proper practice when collecting samples.