From the very beginning of the pandemic, Citadel has been quietly working with hospitals and pathology labs as they scrambled to respond to virus outbreaks.

The company makes software that's been crucial to the COVID response in Australia and the UK, helping process millions of virus tests across both countries.

"The first question from them was - how prepared are you?" chief executive of Citadel Group Mark McConnell told AAP.

"Because if we go down we can't support them, we can't help them through this crisis."

Mr McConnell said when the pandemic first hit, pathology labs didn't have anywhere near the capacity to process enough COVID tests, so his company helped them bring large amounts of new testing equipment online.

Citadel's lab software, Evolution, is used in almost half of the public pathology labs in Australia, including across the Queensland public health system, in dozens of NSW labs, and in major Victorian public hospitals.

The general manager of the group's health division Stephen Lynch explains that its UK arm has helped develop large-scale labs that will soon be able to process up to a million COVID tests every day.

And anyone who has finished a period of COVID isolation with the good news of a negative result via text message, has Citadel to thank - because it developed that process too.

"Technology is an important part of the puzzle to respond well," Mr Lynch told AAP.

"We put systems in place so people can get their results as soon as possible."

So it was to be expected that health authorities were impressed with the speed of the company's response on Tuesday, when one employee turned out to be a close contact of the Melbourne virus case, and later tested negative.

"It would be a cruel irony if we were not drinking our own Kool Aid," Mr McConnell said.

With solid IT a crucial part of the pandemic response, he believes the company he founded has played a small but significant role in the global fight against the virus.

"This is an Australian success story... We've toiled away for the best part of 20 years," he says.

"The convergence of health and IT has never been more pronounced."

Citadel was acquired by Pacific Equity Partners in late 2020, de-listing from the ASX valued at $530 million, and is now worth significantly more.

Mr McConnell said the company is now competing with global tech giants.

"Australian companies are doing very well globally...we are taking good Australian IT to the world," he said.

But he'd like to see more support for Australian tech - and says the recent federal budget could have done more in this area.

While the group also works in defence and education IT, pathology makes up about two thirds of the business.

And with the majority of GP appointments resulting in a blood test, the demand for pathology services is only going to grow.

"You can't escape pathology, it's part of everyone's lives," Mr McConnell said.

Australian Associated Press