"thorough interest" is correct and usable in written English.
You could use it to describe an intense level of interest, such as in the following example sentence: "He had a thorough interest in sculpting which led him to pursue an art degree."
The IARC paper had relied "on open and transparent procedures by independent scientists who completed thorough conflict of interest statements and were not affiliated or financially supported in any way by the chemical manufacturing industry," the scientists' letter said.
Bloomberg News and The Hill broke the news about the delay, and all signs point to the fact that State's "inquiry" has morphed into a thorough conflicts-of-interest investigation into ERM's financial ties to TransCanada and other scandals.
In the interest of thorough reporting, a set of $1.49 tongs was purchased on East 23rd Street and, along with a stopwatch, taken down the block to the Grand Saloon, a neighborhood bar and grill.
So in the interests of thorough research – and thorough research alone – I invited a gentleman friend of greater stature to stop by and give me the verdict from his rather more lofty perspective.
I'd never been much of a whisky drinker, but in the interests of thorough journalism I thought I'd pay a visit to one of Australia's most famous distilleries.
Similarly, there can be no hope of a return to vibrant capitalism unless there is a sweeping housecleaning at the Federal Reserve and a thorough renunciation of its interest-rate fixing, bond buying and recurring bailouts of Wall Street speculators.
And right now, our primary interest remains the thorough destruction and disruption of Al Qaeda and related terrorist networks.
On Jan . 6Lubrizol's board had an "extensive and thorough discussion" about Berkshire's interest and hired advisers.
In the interest of being thorough, he sought out colleagues to confirm the existence of the olinguito in its natural habitat, which took years.
Propose to study a problem of real scientific interest, demonstrate a thorough awareness of the relevant literature, and prepare a work plan with a promising scientific approach.
