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Turnaround time is, probably, the most discussed indicator in any laboratory management meeting. TAT appears in operational targets, in contract clauses with insurers and hospitals, and in the sales material of practically every diagnostic network that presents itself as fast and reliable. It is the indicator everyone measures and that everyone thinks they understand.
The problem is that TAT, in practice, is frequently measured in a way that hides exactly what matters from a clinical standpoint. The number exists, is reported, meets the target. And the result may still be arriving too late for the decision it was supposed to sustain.
What the average hides
The most common way to report TAT is the network average over a period. That average is comfortable: it produces a single number, comparable month to month, easy to place on a dashboard. And it is precisely because it is an aggregate average that it hides the information that decides whether the laboratory is serving clinical decisions well.
The network average dilutes the dispersion between units. A network whose average TAT for a test is four hours may have units operating consistently at two hours and others at eight, and the average hides that half the operation is delivering results in double the acceptable time. The average also hides the tail of the distribution, which is frequently where the clinical risk lies. It isn't the median test that generates the adverse event: it is the test that took far longer than expected, and that test disappears inside an average that looks healthy.
The literature on quality indicators in laboratory medicine is explicit about this point. Plebani and colleagues argue that quality indicators need to be defined and measured in a harmonized way to be comparable and clinically meaningful, and that the absence of that harmonization compromises the indicator's ability to reflect real performance.¹ An average TAT without visibility into the distribution is an indicator that appears to inform, but doesn't inform what management needs to know.
The problem of the start point and the end point
Even before discussing how TAT is aggregated, there is a more fundamental question: what exactly is being measured between two points. A TAT is the difference between an initial moment and a final moment, and both the start and the end are defined in ways that vary between laboratories, between units of the same network, and sometimes between shifts of the same unit.
The start point can be the moment of collection, the moment of sample receipt at the laboratory, or the moment of technical acceptance after triage. Each of these definitions produces a different TAT for exactly the same operation. A laboratory that measures from technical acceptance is systematically excluding the time between collection and acceptance, which can be significant, and reporting a TAT that looks better than the real experience of the patient and the physician.
The end point is even more problematic. TAT is frequently measured up to the moment of result release in the LIS. But release in the LIS is rarely the moment the result becomes clinically useful. Between release and the moment the physician effectively becomes aware of the result, there is an interval that can be minutes or hours, depending on how the result is communicated, whether there is active notification, whether the result enters the electronic health record in structured form. TAT measured up to release in the LIS may be masking a significant delay between the result existing and the result mattering.
The consequence is that two laboratories can report the same TAT and be delivering completely different clinical experiences, simply because they define the start and end of the measurement in distinct ways. And a network may be comparing the TAT of its own units without realizing the units are measuring different things under the same name.
TAT in business hours and the patient who falls ill on Saturday
One of the most common distortions in TAT measurement is accounting in business hours. A laboratory that measures TAT excluding weekends and holidays produces a number that looks consistent, but that hides the reality that a test collected on Friday afternoon may only be released on Monday, and that for the patient and the physician that three-day interval is the real TAT, regardless of how many of those hours were business hours.
For routine tests, that distortion may be tolerable. For tests that sustain time-sensitive clinical decisions, it is serious. Disease doesn't respect the laboratory's commercial calendar, and the patient who falls ill on Saturday needs a result on Saturday. A TAT indicator that systematically excludes weekend time is optimizing for the appearance of efficiency, not for the clinical usefulness of the result.
The literature on TAT in laboratory medicine recognizes that the definition and measurement of the indicator need to be aligned with the clinical use of the result, and that measurements misaligned with that use produce indicators that satisfy operational targets without serving the clinical purpose.² TAT is only a good indicator when it measures the time that effectively matters for the decision the result sustains.
Why harmonization is a prerequisite for measuring TAT right
Measuring TAT in a clinically meaningful way requires a condition most networks don't meet: that the events marking the start and end of the measurement be recorded in a semantically consistent way across all units and systems. When one unit records "received" at the moment of physical arrival and another records "received" at the moment of technical acceptance, the same event name corresponds to different moments of the flow, and any TAT calculated over those records is summing intervals that are not equivalent.
This is, in essence, a problem of semantic harmonization. The events of the laboratory flow, collection, receipt, acceptance, processing, release, communication, need to have consistent semantic identity across systems so that the time between them is comparable. Without that harmonization, the aggregate TAT of a network is the sum of measurements that look alike but measure different things, and the resulting indicator describes an operation that doesn't exist.
The semantic harmonization of flow events is what allows, first, defining with precision the clinically relevant start and end points, and second, measuring the time between them consistently across units. Only on that basis is it possible to analyze the distribution instead of the average, identify the tail where the risk lies, and separate routine TAT from the TAT of time-sensitive tests. Harmonization is not a refinement of the TAT indicator. It is the condition for the indicator to mean what it claims to mean.
This is where OpenHealth Technologies operates. The platform automatically correlates multiple data streams with rigorously validated logical layers of laboratory tests, semantically harmonizing the events of the laboratory flow across units and systems, so that the start point and end point of each TAT measurement are consistent and clinically meaningful. For diagnostic networks, this means TAT stops being an aggregate average that hides dispersion and becomes an indicator that describes the real operation, with the distribution visible, the risk tail identifiable, and the separation between the time that looks efficient and the time that actually serves the clinical decision.
Learn how your network can transform TAT from an indicator that satisfies targets into an indicator that describes the time that truly matters for the clinical decision.