What was the growth rate of 2-year trends in the clinic in Q1 compared to Q4
t we're advancing investment in the business. So maybe Jay can talk a bit about that.
Jay Mazelsky -- President and Chief Executive Officer
Yes, sure. So just a couple of things to build on Brian's comments. Obviously, we're in a high-growth environment and there's excellent opportunity to continue to support that growth. We do that, obviously, in areas like reference labs and in production and field support. And the other area of opportunity for us is just our international markets. We've identified this as being very attractive, and we continue to advance our expansions where it makes sense. We know that there's pretty good short-term return on those expansions. We have, I think, really optimized our ability to identify all the right pieces you need to have in place, including additional field personnel at the reference labs, information technology investments, those type of things. So we're very optimistic about the opportunity short-term and longer-term in our markets, US as well as international, and we'll continue to advance as we see opportunities before us.
Michael Ryskin -- Bank of America -- Analyst
Great. Thanks. And then if I could throw in a follow-up sort of on some of the underlying figures you provide for market conditions. As always, the snapshot is very helpful in terms of visit growth and revenue growth for practices. I'm just curious, looking at it in more granularity, it seems like you're actually seeing continued acceleration from 4Q both on a raw numbers basis, and if you adjust for some of the comp I think -- I guess I'd say that we were expecting a little bit more moderation and maybe a gradual phase as you go through the year, but it seems like there's no indication of that. Is that a fair analysis of the data? Have you seen anything that would indicate that things are moderating a little bit as some of these markets sort of come out from COVID, and we're seeing some reopening of the economy? Just wondering if you could talk about sort of the underlying trends there?
Brian P. McKeon -- Executive Vice President, Chief Financial Officer, and Treasurer
I would say, overall, Mike, the theme would be more consistency than change. What we saw in 2020 was an improvement, if you break down the drivers of things like CAG Diagnostic revenue growth in the clinic. We saw higher levels of contribution from frequency and utilization and those have sustained. If there was one thing that improved a bit in Q1, which we highlighted in the comments, was the new patient contribution to clinical visit growth was up about 100 basis points. So I think some of the building effect of the new puppies and kittens helped.
But adjusting for that, the 2-year growth rates were largely consistent with Q4. It was more consistency than change. We're entering a period now where we'll have the COVID compares. The growth rate numbers are a little tougher to fall, so we're trying to highlight some of the 2-year trends. And I think we're encouraged that the 2-year trends are holding up well, and that's factored into our outlook for the balance of the year.
Jay Mazelsky -- President and Chief Executive Officer
I would just add to that, Mike, the trends we described -- the broader level trends we've described, have largely been intact. So these are obviously new clinical business growth driven by new patients, the majority of which are puppies and kittens, higher usage and intensity of diagnostics and more of a pivot to services by the veterinarians. So those that we have seen over the last second half of 2020, we continue to see in Q1.
Brian P. McKeon -- Executive Vice President, Chief Financial Officer, and Treasurer
Well, one thing I'd highlight in addition to the market trends is in terms of IDEXX's execution, our international teams are really doing an excellent job. We had excellent instrument placements, growth in 360. I think the global commercial model that we've been looking to leverage and build upon is really, really in a good place, and we're very pleased with the international momentum. So I wanted to highlight that.
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t we're advancing investment in the business. So maybe Jay can talk a bit about that.
Jay Mazelsky -- President and Chief Executive Officer
Yes, sure. So just a couple of things to build on Brian's comments. Obviously, we're in a high-growth environment and there's excellent opportunity to continue to support that growth. We do that, obviously, in areas like reference labs and in production and field support. And the other area of opportunity for us is just our international markets. We've identified this as being very attractive, and we continue to advance our expansions where it makes sense. We know that there's pretty good short-term return on those expansions. We have, I think, really optimized our ability to identify all the right pieces you need to have in place, including additional field personnel at the reference labs, information technology investments, those type of things. So we're very optimistic about the opportunity short-term and longer-term in our markets, US as well as international, and we'll continue to advance as we see opportunities before us.
Michael Ryskin -- Bank of America -- Analyst
Great. Thanks. And then if I could throw in a follow-up sort of on some of the underlying figures you provide for market conditions. As always, the snapshot is very helpful in terms of visit growth and revenue growth for practices. I'm just curious, looking at it in more granularity, it seems like you're actually seeing continued acceleration from 4Q both on a raw numbers basis, and if you adjust for some of the comp I think -- I guess I'd say that we were expecting a little bit more moderation and maybe a gradual phase as you go through the year, but it seems like there's no indication of that. Is that a fair analysis of the data? Have you seen anything that would indicate that things are moderating a little bit as some of these markets sort of come out from COVID, and we're seeing some reopening of the economy? Just wondering if you could talk about sort of the underlying trends there?
Brian P. McKeon -- Executive Vice President, Chief Financial Officer, and Treasurer
 I would say, overall, Mike, the theme would be more consistency than change. What we saw in 2020 was an improvement, if you break down the drivers of things like CAG Diagnostic revenue growth in the clinic. We saw higher levels of contribution from frequency and utilization and those have sustained. If there was one thing that improved a bit in Q1, which we highlighted in the comments, was the new patient contribution to clinical visit growth was up about 100 basis points. So I think some of the building effect of the new puppies and kittens helped.
But adjusting for that, the 2-year growth rates were largely consistent with Q4. It was more consistency than change. We're entering a period now where we'll have the COVID compares. The growth rate numbers are a little tougher to fall, so we're trying to highlight some of the 2-year trends. And I think we're encouraged that the 2-year trends are holding up well, and that's factored into our outlook for the balance of the year.
Jay Mazelsky -- President and Chief Executive Officer
I would just add to that, Mike, the trends we described -- the broader level trends we've described, have largely been intact. So these are obviously new clinical business growth driven by new patients, the majority of which are puppies and kittens, higher usage and intensity of diagnostics and more of a pivot to services by the veterinarians. So those that we have seen over the last second half of 2020, we continue to see in Q1.
Brian P. McKeon -- Executive Vice President, Chief Financial Officer, and Treasurer
Well, one thing I'd highlight in addition to the market trends is in terms of IDEXX's execution, our international teams are really doing an excellent job. We had excellent instrument placements, growth in 360. I think the global commercial model that we've been looking to leverage and build upon is really, really in a good place, and we're very pleased with the international momentum. So I wanted to highlight that.
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