How Clinics Can Reduce Sample Rejection Rates by Using Butterfly Needles
, by Andrew Odgers, 12 min reading time
Quality Improvement
How Clinics Can Reduce Sample Rejection Rates by Using Butterfly Needles
Sample rejection is a measurable quality indicator for every phlebotomy service. High rejection rates cost staff time, delay results, cause repeated patient venepuncture, and in acute settings can affect clinical decisions. Switching to butterfly needles for the right patient groups and collection sites is one of the most direct and evidence-backed interventions available to a clinical service looking to reduce its rejection rate.
The starting point
Understanding what drives sample rejection
Why samples are rejected
Laboratory samples are rejected for several pre-analytical reasons. Haemolysis is the most common, accounting for the majority of pre-analytical rejections in most services. Clotted samples in anticoagulant tubes, underfilled tubes, mislabelled samples, and samples collected in the wrong tube are the other main rejection categories. Of these, haemolysis and clotted samples are the categories most directly influenced by the choice of collection device and technique.
Haemolysis rejection rates of between 3 and 10 percent of total samples are commonly reported in hospital laboratory data. In emergency departments and acute settings the rate can be higher. Even a modest reduction in haemolysis rejection has a large absolute impact in a high-volume service because the numbers compound quickly.
Where butterfly needles have the greatest impact
The evidence consistently shows that butterfly needles reduce haemolysis rates most substantially in patients with difficult or fragile vein access. Emergency department collections, hand and foot vein collections, collections from elderly patients, and collections from patients with oncology, haematology, or renal backgrounds are the groups where rejection rates are highest and where switching to butterfly needles produces the most measurable quality improvement.
In routine outpatient phlebotomy from healthy adults with good antecubital veins, the reduction in rejection rate from switching to butterfly needles is smaller. A targeted protocol that focuses butterfly needle use on the highest-risk collections produces the greatest quality improvement for the least additional device cost.
The improvement plan
A practical protocol for reducing rejection rates
The following steps translate the evidence into a structured quality improvement programme that any phlebotomy service can implement.
- Establish your baseline rejection rate by collection type. Request a haemolysis rejection report from your laboratory information system broken down by collection site, patient group, ward or department, and if possible by collector. This baseline is the starting point for measuring any improvement and for identifying where the problem is concentrated. Most laboratory quality systems can produce this report, though it may require working with the laboratory quality manager to set up the correct query.
- Identify your highest-rejection cohorts. In most services, a disproportionate share of rejections comes from a relatively small number of collection contexts: emergency department collections, ward collections from elderly patients, hand vein collections, and high-dependency unit collections. Targeting butterfly needles on these specific groups concentrates the intervention where it will have the greatest impact on your overall rejection rate.
- Mandate butterfly needles for hand and foot vein collections service-wide. This is the single most impactful protocol change for most services. Hand vein collections with straight needles have substantially higher haemolysis rates than equivalent butterfly needle collections. A service-wide rule requiring butterfly needles for all non-antecubital collections removes the individual variation in practice that currently drives a significant proportion of rejection events.
- Introduce the discard tube step as a mandatory protocol element. If butterfly needle collections are already in use but the discard tube step is not consistently followed, enforcing this step will reduce haemolysis in butterfly needle collections where the air-blood interface in the tubing was previously contributing to rejection. This is a no-cost intervention that requires only a protocol update and staff briefing.
- Train on gauge matching for narrow-gauge collections. Ensure all phlebotomists understand that 25 gauge butterfly needle collections should use paediatric tubes rather than standard adult vacutainer tubes. The vacuum mismatch between a 25 gauge needle and a standard adult tube is a preventable cause of haemolysis that training alone can eliminate without any additional equipment cost.
- Re-measure rejection rates after 8 to 12 weeks. Run the same laboratory rejection report after implementing the protocol changes and compare against your baseline. Stratify by the same collection type and patient group categories as the baseline report. In services where the protocol changes have been consistently applied, a measurable reduction in haemolysis rejection rates in the targeted groups is typically visible within this timeframe.
- Share results with clinical and procurement teams. A documented reduction in rejection rates is the evidence that justifies both the continued investment in butterfly needles and any further protocol expansion. It also supports any CQC or accreditation documentation that references pre-analytical quality metrics.
Technique matters too
Why device alone is not enough
The discard tube is non-negotiable
The most common source of haemolysis in butterfly needle collections that should not be haemolysed is the omission of the discard tube. If your rejection rate data shows butterfly needle collections producing haemolysed samples at a rate that seems inconsistent with the clinical evidence, the first question to ask is whether the discard tube step is being consistently followed. Audit this through direct observation of practice rather than self-reporting, as omission of the step tends to be habitual and practitioners may not be aware they are doing it.
Gauge selection discipline
A 21 gauge butterfly needle used on a vein that calls for a 23 gauge will produce trauma and possible haemolysis despite being the correct device type. Device selection at the gauge level matters as much as device type selection. If your haemolysis data shows elevated rates in butterfly needle collections from a specific population, review whether gauge selection for that group is appropriate and whether staff have the confidence and authority to select the narrower gauge when the vein calls for it.
Tube order compliance
Sample contamination from incorrect tube order is a rejection cause that has nothing to do with the collection device. Butterfly needle protocol improvements should be implemented alongside a review of tube order compliance. Combining both interventions produces a larger overall reduction in rejection rate than either alone.
Start improving today
Butterfly needles ready to ship to your clinic or service
Charles Medical supplies safety-engineered butterfly needles across all clinical gauges with next-day UK delivery. No minimum order and volume pricing available for service-level procurement.
The financial case for this quality improvement is set out in full in our Cost Analysis: Are Butterfly Needles Worth the Investment guide.
Part of the hub
Back to the Butterfly Needle Knowledge Hub
This article is part of our complete butterfly needle knowledge base, covering clinical use, gauge selection, technique, haemolysis reduction, cost analysis, patient guidance, and the full regulatory picture for UK procurement.
Keep reading
Related guides in this hub
Clinical Evidence: Studies Showing Reduced Haemolysis with Butterfly Needles provides the research background behind the protocol recommendations in this guide. Common Mistakes with Butterfly Needle Use covers the technique failures that undermine protocol improvements. And Cost Analysis: Are Butterfly Needles Worth the Investment builds the financial case from the rejection rate data.
Frequently asked
Sample rejection and butterfly needle questions answered
What is an acceptable haemolysis rejection rate for a phlebotomy service?
There is no universally mandated threshold, but rates above 2 to 3 percent are generally considered high in routine outpatient phlebotomy services and warrant investigation. Emergency department and acute inpatient services often run higher rates because of their patient mix. Whatever the baseline, a measurable downward trend following a protocol improvement intervention is the goal. Your laboratory quality team will have the relevant benchmarks for your service type.
How quickly can rejection rates improve after switching to butterfly needles?
In services where the protocol change is consistently implemented, changes in rejection rates are typically measurable within 8 to 12 weeks, which gives enough collection volume for the data to be statistically meaningful. The improvement is most rapid in services where a high proportion of collections are in the high-risk categories where butterfly needles have the greatest impact.
Will using butterfly needles everywhere eliminate haemolysis rejections?
No. Butterfly needles reduce haemolysis from collection-related mechanical causes, but other causes of haemolysis remain. Samples that are transported incorrectly, centrifuged too vigorously, or left too long before processing will haemolyse regardless of the collection device. A comprehensive pre-analytical quality programme addresses all stages of the sample journey, not just collection.
Should I audit butterfly needle technique as well as rejection rates?
Yes. Rejection rate data tells you whether the outcome has changed but not why. Direct observation of practice, including discard tube compliance, gauge selection, tube order, and post-collection tube mixing, identifies technique issues that may be preventing the full benefit of butterfly needle use from being realised. Combining outcome data with technique audit gives the most complete picture for a quality improvement programme.