Turnaround time (TAT) in a laboratory is the time from a defined starting point, such as test request or sample receipt, to a defined end point, such as a verified result being available to the clinician. Because the start and end points vary, every lab must state exactly which interval it measures before it can monitor or improve TAT.
Clinicians judge a lab largely on speed and reliability. A correct troponin result that arrives too late can still delay treatment, extend emergency department stays and push doctors towards point-of-care devices with weaker quality oversight.
This guide explains how to define and measure TAT properly, set targets with clinicians and fix the delays that matter.
Defining TAT: brain-to-brain vs lab TAT
The brain-to-brain loop, a concept described by George Lundberg, starts when a clinician decides a test is needed and ends when they act on the result. It is the TAT that matters to patients, but the lab controls only part of it.
Laboratory TAT usually runs from sample receipt in the lab to result verification. It is easy to measure but can look good while the patient still waits, because delays in collection, transport and result viewing are invisible.
Break TAT into phases so you can see where time is lost:
- Pre-analytical: order, collection, labelling, transport, receipt, registration, centrifugation
- Analytical: loading, analysis, reruns, dilutions, QC holds
- Post-analytical: technical review, verification, release, communication of critical results, clinician viewing
How to measure TAT
Reliable measurement depends on timestamps. Your LIS and hospital system should capture order time, collection time, lab receipt, analysis and verification. Check that each timestamp reflects a real event: a collection time typed in later from memory, or a receipt time recorded only when the batch is registered, will distort the data.
Report TAT as a median and a 90th percentile, not just an average. The mean is pulled by a few extreme delays, while the 90th percentile shows what one patient in ten experiences. Many labs also report the percentage of results meeting the target.
Do not delete outliers. A sample that took six hours may reveal a lost tube, a broken analyser or a request sitting unregistered. Review outliers separately, but keep them in the indicator.
STAT vs routine
Measure STAT (urgent) and routine work separately, and by location: emergency department, wards, intensive care and outpatients. A combined figure hides the problem. Also check STAT requests are genuinely urgent, because if everything is marked STAT, nothing is.
Setting TAT targets with clinicians
Targets should reflect clinical need, not what the lab currently achieves. Agree them with emergency physicians, intensivists and ward teams, record them in service agreements or the user handbook, and review them periodically.
Where professional guidance exists, use it. Cardiology and laboratory medicine guidance has long recommended that troponin results be available within about 60 minutes of sample collection; check current guidelines and agree local targets with your cardiologists.
What ISO 15189:2022 expects
ISO 15189:2022 expects labs to define examination turnaround times that reflect clinical needs, monitor whether they are met and inform users of significant delays. TAT is also one of the most common quality indicators a lab uses to evaluate its performance and feed management review. Assessors typically ask how targets were set, how often performance is reviewed and what happened when targets were missed. For accreditation-specific expectations, check with your accreditation body.
Common causes of delay and how to fix them
| TAT phase | Common delays | Improvement ideas | Metric |
|---|---|---|---|
| Pre-analytical | Delayed collection, batched porter runs, unlabelled tubes, slow registration | Pneumatic tube system, dedicated STAT runs, labelling at the bedside, registration on receipt | Collection to receipt time |
| Analytical | Clotting time for serum tubes, centrifuge queues, analyser downtime, reruns | Plasma tubes where validated, short-spin protocols where validated, backup analyser plan, maintenance outside peak hours | Receipt to result time |
| Post-analytical | Results waiting for manual verification, delayed critical result calls | Autoverification rules, verification queues by priority, clear call escalation | Result to verification and verification to clinician viewing |
| Whole process | Staffing gaps at shift change, unclear ownership | Staffing matched to demand peaks, a named TAT owner, daily review | Median, 90th percentile, percentage within target |
Lean thinking and batching
Lean methods help you map the process and remove waiting. Walk a sample from bedside to report and time each step. You will often find samples waiting for a full centrifuge load, a porter run or a batch release. Small batches or single-piece flow for urgent tests usually beat large batches.
Autoverification
Autoverification releases results that meet defined rules, such as no flags, QC in control, results within limits and delta checks passed, without manual review. It frees scientists to focus on abnormal results. Rules must be validated and documented, and the lab remains responsible for every released result.
Pre-analytical problems such as rejected samples add a full recollection cycle to TAT. See our guides on pre-analytical errors and sample rejection criteria.
Worked example: emergency troponin TAT in a Kochi hospital
A multispeciality hospital in Kochi receives repeated complaints from the emergency department that troponin results are slow. The lab's own figure, receipt to verification, looks acceptable. Emergency physicians agree it is the wrong measure.
The quality manager pulls three weeks of LIS data from collection to verification and splits it by phase. The median is close to target, but the 90th percentile is far over it. Most of the long tail sits before the sample reaches the lab, with a second cluster at night.
A process walk finds three causes. Porters collect samples from the emergency department on a timed round rather than on demand. Troponin is drawn in serum tubes that need clotting time before centrifugation. At night, one scientist covers several sections, so verification waits.
The team works through a root cause analysis and agrees actions. Emergency troponin samples go by pneumatic tube. After verification that the assay performs on lithium heparin plasma, the emergency department switches to plasma tubes. Autoverification rules are validated for troponin results without flags. Night staffing is adjusted for the peak hours shown in the data.
The lab then reports median, 90th percentile and percentage within target to the emergency department each month. The long tail shrinks, and the remaining outliers are reviewed one by one.
Common mistakes
- Measuring only the lab's portion and ignoring collection and transport
- Reporting a mean TAT that hides long delays
- Excluding outliers instead of investigating them
- Setting targets without clinician input
- Combining STAT and routine work in one figure
- Trusting timestamps without checking how they are recorded
- Reviewing TAT data without assigning anyone to act on it
Key takeaway: Define TAT clearly, measure it with reliable timestamps using medians and 90th percentiles, agree targets with clinicians, and fix the phase where time is really lost.
Frequently Asked Questions
What is turnaround time in a laboratory?
Turnaround time is the time taken from a defined start point, such as the test request, sample collection or sample receipt, to a defined end point, usually a verified result being available to the requesting clinician. Labs should state which interval they measure, because brain-to-brain TAT and laboratory-only TAT can give very different pictures.
How can a lab improve its TAT?
Start by measuring TAT in phases with reliable timestamps, then find where time is lost. Common fixes include pneumatic tube transport, dedicated runs for urgent samples, plasma tubes where validated, reducing batching, validated autoverification rules and staffing matched to demand peaks. Agree targets with clinicians and review performance regularly.
Why use the 90th percentile for TAT?
The 90th percentile shows the time within which 90% of results are delivered, so it reveals the delays that one patient in ten experiences. A mean can be distorted by a few extreme values and a median ignores the long tail. Reporting the median and 90th percentile together gives a fair picture of typical and worst-case performance.
Is TAT a quality indicator?
Yes. TAT is one of the most widely used laboratory quality indicators because it reflects how well the service meets clinical needs. ISO 15189:2022 expects labs to define turnaround times, monitor them and use quality indicators to evaluate performance. Results should feed management review and trigger action when targets are missed.
What is the difference between STAT and routine TAT?
STAT requests are urgent and need results quickly for immediate clinical decisions, such as troponin, potassium or blood gases in emergencies. Routine requests have longer agreed targets. Measure and report them separately, and audit STAT use, because overuse of the STAT category slows the samples that are genuinely urgent.
Next steps
To build TAT monitoring into a wider quality system, our Laboratory Quality Management System course covers quality indicators, process control and improvement. For related reading, see our pre-analytical errors checklist, sample rejection criteria and 5 Whys vs fishbone. If you would like help choosing a course, speak to a counsellor.
Looking for structured certification?
Explore Innoryx courses or speak to a counsellor about the right program for you.