How to Set TAT for your Tests? | Know Laboratory TAT Importance

By Godavari Doke

Sr. Content Writer

What is Turnaround Time?

The time taken for the delivery of a service is termed lab Turnaround Time or laboratory TAT. In a medical lab, test turnaround time is the amount of time from patient registration to report delivery. Mainly, the importance of turnaround time in a medical laboratory is to help you define & measure the efficiency of your lab’s service delivery. Hence, it is considered a key performance indicator for medical labs.

TAT full form: Turnaround Time. Lab turnaround time is the elapsed time between the start event your lab has defined, usually registration or sample collection, and delivery of the verified report. It is measured separately for every test, never as one figure for the whole lab.

The higher the lab Turnaround Time, the poorer the quality of service delivery. Therefore, for diagnostic centers, calculating, improving, and managing the laboratory TAT is the key to providing timely patient delivery.

How to Calculate Turnaround Time in a Medical Laboratory for Your Tests?

The laboratory TAT (turnaround time) is measured from when the sample is collected to when the report is delivered. This parameter varies for each test since diagnostics and pathology cover a wide spectrum. For example, a molecular lab test turnaround time will be longer than a clinical pathology TAT. Therefore, to measure it for a wide range of tests, having a diagnostics lab solution becomes very important.

There are three principal parts of this metric, namely –

• • Pre-analytical TAT – The time between patient registration and sample collection to sample accessioning is the pre-analytical laboratory TAT
  • Analytical TAT – The time required to process a sample is the analytical laboratory TAT
  • Post-analytical TAT – The time needed for report generation, interpretation, approval, and delivery is termed post-analytical laboratory TAT in the laboratory business

You should record all three parameters for every test to create a master list. Then compare these recordings to the system-generated TAT in the lab. You can also get the average TAT value, and note and compare it every day to understand your lab’s performance. This everyday recording can be stated as the expected TAT in the lab.

Lab Turnaround Time Formula

Total TAT = report delivery time minus registration or collection time. Pre-analytical TAT = accessioning time minus collection time. Analytical TAT = result time minus accessioning time. Post-analytical TAT = report delivery time minus result time. The three phases always add up to the total.

Worked Example: TAT for Five CBC Samples

A single sample tells you very little. The pattern across samples is what you set targets on. Here are five CBC samples from one morning at a collection-center-fed lab.

The same five numbers give three very different answers, depending on which statistic you pick:

• Mean: 133 minutes, pulled upward by one slow sample (S5).
• Median: 105 minutes, which is what a typical patient actually waited.
• 90th percentile: 198 minutes, which is the figure you can safely promise.

S5 is the one to investigate. If it waited for a courier run or sat unverified, that is a process gap, not an analyzer problem.

Always paste the date along with the time. A sample collected at 23:40 and reported at 01:15 shows a negative TAT if the sheet holds only the clock time.

It is highly important that you understand the importance of turnaround time in a medical laboratory to deliver the best experience to your patients & clients.

How to Set Expected TAT for Each Test: 5 Steps

Expected TAT is a promise to clinicians and patients, so it should come from your own data, not from a competitor’s brochure. These five steps turn a raw timestamp export into a test-wise master list.

1. Group your tests: sort the menu into routine, batched, STAT, and send-out categories.
2. Pull four to eight weeks of data: export start and delivery timestamps for every test.
3. Find the 90th percentile: use it as the starting expected TAT for each test.
4. Adjust for run schedules: a test run once daily cannot promise same-hour reports.
5. Publish and review quarterly: share the list with referrers and tighten it as you improve.

A master list built this way looks like the example below. The values are illustrative. Your own export decides the real numbers.

What the literature suggests: A review of laboratory TAT by Hawkins in The Clinical Biochemist Reviews (2007) proposes a 90% completion time of under 60 minutes, from sample registration to result reporting, as an initial goal for common laboratory tests. Much of the evidence it draws on comes from hospital and emergency testing, so outpatient labs fed by distant collection centers usually set wider targets.

How to Calculate TAT in Excel

Most labs can export registration and delivery timestamps from their LIMS into a spreadsheet. Set up the sheet like this:

1. Column B, start time: paste the full date and time of collection or registration.
2. Column C, delivery time: paste the full date and time the report was delivered.
3. Column D, TAT in minutes: enter =(C2-B2)*1440 and copy it down every row.
4. Column E, expected TAT: enter the target in minutes for that test.
5. Column F, status: enter =IF(D2>E2, “Breached”, “Within TAT”) and copy it down every row.
6. Summary cells: use =MEDIAN(D2:D500) and =PERCENTILE.INC(D2:D500,0.9) to summarize each test separately.

Always paste the date along with the time. A sample collected at 23:40 and reported at 01:15 shows a negative TAT if the sheet holds only the clock time.

What happens when laboratory TAT is exceeded?

The lab test turnaround time may vary depending on the processes and machines (analyzers), as per sample type, total or partial lab automation, and many other reasons. Despite considering the above factors for calculation, if a lab exceeds its expected medical TAT, it indicates a problem. Hence, recording and measuring this parameter in your system is highly essential.

Know the importance of turnaround time in medical laboratories here.

An expected TAT helps with the following –

• • Decision Making – Knowing which medical TAT-exceeded tests, labs can monitor the dependent aspects and make better decisions on optimizing it.
  • Improves Process Cycle & Prioritization – TAT-exceeded reports must be prioritized to fix issues at the earliest.

TAT Breach Reason Codes to Log Every Time

A breach without a reason is a number nobody can act on. Ask staff to pick one code whenever a report crosses its expected TAT, and review the totals each week.

Clinical & Business Advantages Of Optimized Laboratory TAT

• Clinical Advantage of Lab Test Turnaround Time Control

  • Quick turnaround time in medical laboratories helps labs to offer a clinical advantage, especially to hospitals, facilitating faster diagnosis for patients that require immediate care.
  • On-time report delivery makes it easier for clinicians to attend to patients without delays. Digital reporting with optimal medical TAT makes that possible.
  • Improved medical TAT fastens report delivery to patients seeking medical help.

• Business Advantage Of Optimized Lab Turnaround Time

  • Improves and doubles your throughput, enhancing performance
  • Improves testing capacities, improving revenue cycles
  • Enhances the overall experience of doctors and patients

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