Brian McKeon
Chief Financial Officer at IDEXX Laboratories
Good morning everyone. I'm pleased to take you through our fourth quarter and full year 2023 results and to provide an overview of our financial outlook for 2024. IDEXX had a strong finish to 2023, reflected in our fourth quarter performance. Revenues increased 8% organically, supported by 10% organic gains in CAG diagnostic recurring revenues, net of a 1% growth headwind from fewer equivalent selling days. Operating profits increased 8% as reported and 10% on a comparable basis, benefiting from solid gross margin gains and opex leverage.
These factors and a lower than expected effective tax rate supported delivery of $2.32 per share in EPS in Q four of 17% on a comparable basis. IDEXX execution enabled delivery of strong full year financial results reflected in 9% overall organic revenue growth and high comparable operating margin gains. This supported a 29% increase in EPS for the full year on a comparable basis, including 12% of combined EPS growth, benefit from a customer contract resolution payment and the lapping of discrete 2022 R and D investments.
These results were driven by 10.5% full year organic growth in CAG diagnostic recurring revenues, reflecting 11% organic gains in the US and 10% organic growth in international regions aligned with our original full year growth targets. We also achieved 19% full year organic growth in recurring software and digital imaging revenues, sustained high customer retention levels, and placed a record number of CAG premium instruments, which drove an 11% expansion of our global premium installed base.
These strong execution trends position us well as we enter 2024 and advance our growth strategy. This year we're targeting 10% organic revenue growth at the high end of our initial guidance range of 7% to 10% overall organic revenue growth, supported by 7.5% to 10.5% organic gains in CAG diagnostic recurring revenues. We're also planning for solid comparable operating margin gains, building on our long term track record supporting continued high comparable EPS growth. We'll walk through the details of our financial guidance later in my comments.
Let's begin with a review of our fourth quarter results. Fourth quarter organic revenue growth of 8% was driven by 9% organic gains in our CAG business. CAG diagnostic recurring revenue increased 10% organically in Q four, reflecting 9% gains in US and 12% growth in international regions, net of a 1% global growth headwind from equivalent days effects. CAG diagnostic organic recurring revenue growth in Q4 was supported by average global net price improvement of 6% to 7%, with US net price gains at the low end of this range. IDEXX execution drivers supported volume gains of 4% in both US and international regions normalized for days effects, reflecting an improvement from Q3 volume growth levels and the strongest normalized volume growth quarter in 2023.
IDEXX CAG diagnostics recurring revenue growth remained solidly above sector growth levels. In the US CAG diagnostic recurring revenue increased 9% organically, net of 1% negative growth rate impact from fewer equivalent selling days in Q4. This reflects a 1050 basis point normalized growth premium compared to US clinical visit growth levels, which declined an estimated 0.5% in the quarter on a same store basis. IDEXX execution drivers drove solid US value growth in the quarter reflecting benefits from new business gains, high customer retention levels, and sustained diagnostic frequency levels per visit.
International CAG diagnostic recurring revenue growth was 12% in Q4, reflecting benefits from higher net price realization and improved volume gains. International results were also supported by strong IDEXX execution reflected in continued solid growth in premium instrument placements, which supported a 13% year on year increase in our international premium instrument install base. IDEXX achieved solid organic gains across our major testing modalities in the fourth quarter. IDEXX vet lab consumable revenues increased 13% organically, reflecting double digit gains across US and international regions.
Consumable gains were supported by an 11% increase in our global premium install base in 2023, reflecting strong gains across our catalyst, premium hematology, and set of you platforms. For the full year 2023, we achieved a record 19,000 premium instrument placements with excellent quality reflected in sustained high, new, and competitive catalyst placements. In Q4, we placed 5241 premium instruments up 3% from high prior year levels, driven by strong gains in set of you placements and continued expansion of ProCyte One. Overall CAG instrument revenues declined 3% organically in the quarter, reflecting comparisons to high prior year levels, program pricing effects and global mix.
Rapid assay revenue grew 9% organically in Q4, supported by benefits from net price increases and solid volume gains in the US. Global lab revenues expanded 7% organically, reflecting high single digit gains in the US and sustained solid organic revenue growth in international regions. CAG veterinary software and diagnostic imaging revenues increased 6% organically in Q4 compared to strong prior year levels. Results continued to be supported by double digit growth in recurring revenues and ongoing momentum in cloud-based software placements. For the full year, veterinary software and diagnostic imaging revenues increased 11% organically, supported by 19% organic gain in recurring revenues.
In our other business segments, water revenues increased 5% organically in Q4 compared to strong prior year levels supported by continued solid gains in the US and Europe. Overall growth in the quarter was moderated by lower China revenues and year end order timing. For the full year, water revenues grew 8% overall and 7% organically. Livestock, poultry and dairy revenues decreased 4% organically in Q4 as solid gains in the US, Europe, and Latin America were offset by declines in herd health screening revenues and comparisons to higher prior swine testing levels in China. For the full year, LPD revenues were down 1% organically as solid gains across our core ruminant, poultry, and swine businesses were offset by declines in areas like herd health screening, reflecting regional macro dynamics.
We expect to work through comparison issues in herd health screening post the first quarter of 2024. Turning to the P&L Q4 operating profits increased 8% as reported and 10% on a comparable basis, supported by solid comparable operating margin gains. Gross profit increased 9% as reported and on a comparable basis. Gross margins were 58.4% up 50 basis points on a comparable basis, adjusting for 70 basis points of negative FX impact, primarily related to the lapping of prior year hedge gains.
Gross margin gains reflected benefits from net price improvement, which offset inflationary cost impacts, favorable business mix impacts from strong consumable growth, and higher software service gross margins. Operating expenses were up 9% as reported and 7% on a comparable basis in the quarter, reflecting growth in commercial investments and increases in R and D spending aligned with advancing our innovation initiatives, including our new instrument platforms. For the full year 2023, operating margins were 30%, including approximately 40 basis points of benefit from the Q1 customer contract resolution payment.
On a comparable basis, full year operating margins increased 390 basis points, including 280 basis points of combined benefit from the customer contract resolution payment and the lapping of discrete 2022 R and D investments. For the full year, foreign exchange reduced operating margin gains by 60 basis points, primarily related to the lapping of prior hedge gains. Q4 EPS was $2.32 per share up 17% on a comparable basis. In Q4 EPS benefited from a lower effective tax rate. This reflected the release of valuation allowances in certain jurisdictions, which lowered our full year effective tax rate by approximately 100 basis points and increased EPS by $0.10 per share. Fourth quarter EPS included $0.02 in tax benefits from share based compensation activity and $0.04 in headwind from foreign exchange changes primarily related to the lapping of 2022 hedge gains.
FX hedge gains were $2 million in the quarter. Full year EPS was $10.06 per share, an increase of 29% on a comparable basis, including 12% of combined EPS growth, benefit from the Q1 customer contract resolution payment and the lapping of discrete 2022 R and D investments. For the full year, stock based compensation activity provided $14 million or $0.16 per share in tax benefit, lowering our effective tax rate by 130 basis points. As noted, full year comparable EPS growth also benefited by $0.10 per share, or approximately 1% from the release of tax valuation allowances in certain jurisdictions.
Foreign exchange increased Q4 and full year revenue growth by approximately 1% and 0%, respectively. For the full year foreign exchange reduced operating profits by $25 million and EPS by $0.24 per share, primarily related to the lapping of 2022 hedge gains. In 2023 full year foreign exchange hedge gains were $4 million. Free cash flow was $773 million for 2023 or 91% of net income. Free cash flow conversion was above the high end of earlier projections, reflecting timing and control of capital spending. Capital spending was $134 million for the full year or 3.7% of revenue. Our balance sheet remains in a strong position.
We ended 2023 with leverage ratios of 0.7 times gross and 0.4 times net of cash. Our 2024 interest expense outlook incorporates recent forward interest rates and expectations for similar leverage ratios this year. We allocated $38 million to repurchase 90,000 shares in the fourth quarter. For the full year 2023, we allocated $83 million to repurchase 175,000 shares. Targeted deployment of cash to share repurchases supports our projected 0.5% to 1% reduction in diluted shares outstanding for the full year 2024.
Turning to our 2024 full year outlook, we're providing initial guidance for revenues of $3.930[phonetic] billion to $4.040[Phonetic] billion an increase of 7.5% to 10.5% on a reported basis. On an organic basis, this reflects a growth rate of 7% to 10% overall, supported by 7.5% to 10.5% organic growth in CAG diagnostic recurring revenues. Current exchange rates we expect foreign exchange to have limited impact in full year revenue growth. Our reported revenue growth outlook includes approximately $15 million of projected revenue from our recent software acquisition, which Jay will highlight in his comments.
In terms of the key drivers of our 2024 organic growth outlook, the midpoint of our CAG diagnostic recurring revenue growth range incorporates expectations for global net price gains of approximately 5% and volume gains of approximately 4%, aligned with assumptions for relatively flat US clinical visit same-store growth levels post Q1. As we'll discuss, we have seen some effects from severe US weather trends in January, which we expect will impact overall Q1 clinical visit growth levels.
Our full year outlook reflects US volume growth premium to US clinical visits, aligned with our trends in the second half of 2023, supported by expectations for continued solid global growth benefits from IDEXX execution drivers. The higher end of our CAG diagnostic recurring revenue growth outlook range captures the potential for improved sector visit and same store growth trends and overall IDEXX volume growth potential. The lower end of the range calibrates for potential risk to our targeted growth goals, including effects from macroeconomic conditions. The high end of our overall organic revenue growth guidance of 10% is aligned with our long term goals.
We expect overall organic growth to be constrained somewhat by expectations for modest organic growth at LPD and comparisons to strong prior instrument placement levels. Our reported operating margin guidance for the full year 2024 is 30.2% to 30.7%. On a comparable basis this reflects an outlook for 20 to 70 basis points of improvement in comparable annual operating margins, net of a negative 40 basis point operating margin impact related to the lapping of the Q1 2023 customer contract resolution payment.
We're planning for solid gross margin gains on a comparable basis in 2023, supported by continued strong growth in CAG diagnostic recurring revenues, expansion of our cloud based software business and benefits from lab productivity initiatives. We expect limited impact from foreign exchange on 2024 revenue growth and operating margin at the rates assumed in our press release. We estimate foreign exchange will increase full year EPS by $0.02 per share given current hedge positions. In terms of sensitivities to changes to the foreign exchange rates assumed in our press release, we project that a 1% change in the value of the US dollar would impact full year reported revenue by approximately $13 million and operating income by approximately $4 million net of hedges.
Our 2024 EPS outlook is $10.84 to $11.33 per share. This reflects an increase of 8% to 13% as reported and on a comparable basis net of a 2% EPS growth headwind from the lapping of the customer contract resolution payment and 1% of headwind related to lapping of benefits from tax valuation, reserve releases in 2023. Our EPS outlook factors in a 1.5% increase in our overall effective tax rate to approximately 22% in 2024, reflecting these lapping impacts and lower projected benefits from share based compensation activity. Our EPS outlook captures expected benefits in 2024 from lower interest expense compared to 2023, as well as expectations for reductions in average share count.
Our 2024 free cash flow outlook is for a net income to free cash flow conversion ratio of 90% to 95% aligned with our long term goals. This reflects estimated capital spending of $180 million or approximately 4.5% of revenues. Overall, we're well positioned to deliver continued strong financial performance in 2024. In terms of our operational outlook for Q1, we're planning for overall organic revenue growth of 6% to 8%, factoring in approximately 1% of negative growth impact from severe weather in the US in January and constraints on Q1 growth in areas like LPD related to tougher year-on-year comparisons.
Reported revenue growth should be largely in line with organic revenue growth estimates. In terms of our profit outlook, we're planning for reported operating margins of 29.4% to 29.8% in Q1. This reflects an outlook for flat to moderate expansion in comparable operating margins, adjusting for the lapping of the prior year $16 million customer contract resolution payment recorded in Q1 2023 as an offset to operating expense. That concludes our financial review. I'll now turn the call over to Jay for his comments.