How to measure laboratory turnaround time (TAT)

What does TAT mean in a laboratory?

TAT, short for turnaround time, is the time a laboratory takes to get a result back after a test is requested. In practice it is the elapsed time between two timestamps you choose, such as sample receipt and report available. “TAT in laboratory” work is mostly about choosing those timestamps consistently and then looking at the spread, not a single figure.

TAT is the single number patients, referring doctors and lab owners judge a laboratory on. It is also the number most often quoted carelessly. Three decisions make it useful.

1. Fix the clock

“Turnaround time” can mean any of these, and they can differ by hours:

• Order to report — from when the test is booked. Includes the wait for the patient to be collected.
• Collection to report — from when the sample is drawn. What a patient usually has in mind.
• Receipt to report (also called intra-lab or analytical TAT) — from when the sample reaches the lab. What the lab can actually control.

Pick one as your headline number, define it in writing, and report the intra-lab figure separately so you can tell a lab problem from a logistics problem. Measuring against a collection centre’s pickup schedule is a different conversation from measuring the bench.

2. Stop using the average

The mean TAT hides the cases that generate complaints. A lab reporting a “4 hour average” can still have one report in ten taking twelve hours, and those are the ones the referring doctor remembers. Report the distribution instead:

• Median (P50) — the typical experience.
• P90 / P99 — the slow tail, where the complaints live.
• Percent within target — e.g. “94% of routine reports within 6 hours”.
• An outlier list — the actual cases past target this week, not just a percentage.

3. Break the total into segments

A single end-to-end number cannot tell you what to fix. Timestamp each hand-off and look at the gaps:

• Registration to collection — queue at the front desk or the phlebotomy room.
• Collection to receipt — transport from a collection centre or ward.
• Receipt to accessioning — sorting, centrifuging, sample prep.
• Accessioning to result — time on the analyser or on the bench, including repeats and dilutions.
• Result to verification — the technical and medical validation step. On many days this is the largest gap, and it is a staffing and shift-pattern problem, not a machine one.
• Verification to delivery — printing, dispatch, or the WhatsApp / portal push.

Slice it, don’t just total it

The same report should let you see TAT by test (a CBC and a culture have nothing in common), by shift (the night backlog clearing at 9am), by collection centre, and by referrer. Set separate targets per test category, and separate STAT and routine targets — holding a routine vitamin D to the same clock as a STAT potassium just makes the number meaningless.

An LIS that timestamps every step is what makes this measurable without a spreadsheet exercise every month. For how Raydian LIS reports TAT — P50 / P90 / P99, by test, shift and centre — see the lab analytics page.

For the rest of the lab workflow around turnaround time, see pathology lab software.