This underpins our new 20 by '25 strategy, which alludes to our plans to achieve at least $20 billion of revenue by 2025.
1 in the categories of innovation, capital deployment, global competitiveness, quality of product and services, and long-term investment value.
And of course, it sets us up well to meet our ambitious 20 by '25 targets.
Revenue for the fourth quarter grew 10.2% on a reported basis and 11.6% at constant currency.
The $62 million beat above the midpoint of our guidance range was driven by stronger operational performance across all three segments, as well as higher pass-throughs partially offset by FX headwinds.
Fourth-quarter adjusted EBITDA grew 12.7%, reflecting our revenue growth, as well as ongoing productivity initiatives.
The $27 million beat above the midpoint of our guidance range was entirely due to our operational performance.
Fourth-quarter adjusted diluted earnings per share of $2.55 grew 20.9%.
That was $0.13 above the midpoint of our guidance, with the majority of the beat coming from the adjusted EBITDA drop-through.
This year, 50 new molecules were approved by the FDA and 72 new commercial launches took place.
IQVIA supported nearly 80% of launches by top 20 pharma and approximately 60% of all launches.
There are now over 3,000 clients who have adopted one or more of our technology platforms, including human data science cloud, orchestrated analytics, E360, Omnichannel Navigator, Engage, and of course, Orchestrated Customer Engagement, or OCE.
In fact, the footprint of our OCE platform itself has continued to grow, with over 350 clients having adopted one or more modules on the platform since launch.
Two top 20 pharma clients have successfully rolled out this intelligence engine to orchestrate customer engagements in over 30 countries and across more than 40 brands each.
Two other top 20 pharmas are currently in the implementation phase.
In the quarter, we entered into an enterprise agreement with a top 10 pharma clients to utilize DMD's advanced analytic capabilities to power omnichannel engagement across all eight of their brand franchises.
To date, 18 of the top 20 have adopted at least one of DMD solutions.
In the fourth quarter, we won two large post-authorization safety studies in an autoimmune area with a top 10 pharma.
These studies use existing healthcare data to observe patients over a period of 10 years to better understand long-term effects of the treatment.
During the year, we added 90 new OCT clients, bringing the total to over 350 clients who have adopted one or more modules within our clinical technology suite since launch, including all of the top 10 and 18 of the top one.
Within OCT's digital patient suite this year, we secured three preferred provider partnerships with top 30 pharmaceutical clients to provide our interactive response technology, IRT capabilities, to support site operations across their entire clinical trial portfolios.
Finally, our overall R&DS business continues to build on its strong momentum with over $2.4 billion of net new business, including pass-throughs, and it set a record for quarterly service bookings, achieving over $1.9 billion of service bookings for the first time ever.
This resulted in a fourth-quarter contracted net book-to-bill ratio of 1.36 excluding pass-throughs and 1.24, including pass-throughs.
For the calendar year, we delivered over $10 billion of total net new bookings for the first time ever, an increase of 14.6% compared to 2020.
This led to an LTM contracted net book-to-bill ratio of 1.35 excluding pass-throughs and 1.34 including pass-throughs.
Our contracted backlog in R&DS, including pass-throughs, grew 10.2% year over year to a record $24.8 billion as of December 31, 2021.
Fourth-quarter revenue of $3.636 billion grew 10.2% on a reported basis and 11.6% at constant currency.
In this year's fourth quarter, COVID-related revenues were approximately $325 million, down about 25% versus the fourth quarter of 2020.
Technology and Analytics Solutions revenue for the fourth quarter was $1.496 billion, up 5% reported and 6.6% at constant currency.
Year over year, TAS experienced just over 400 basis points of headwind due to a step-down in COVID-related work.
R&D Solutions fourth-quarter revenue of $1.944 billion was up 15.4% at actual FX rates and 16.3% at constant currency.
Excluding all COVID-related work, organic growth at constant currency and R&DS was approximately 25%.
Contract Sales and Medical Solutions, or CSMS, fourth-quarter revenue of $196 million grew 3.7% reported and 7.4% at constant currency.
For the full year, revenue was $13.874 billion, growing at 22.1% reported and 21.1% at constant currency.
Full-year Technology and Analytics Solutions revenue was $5.534 billion, up 13.9% reported and 12.4% at constant currency.
Full-year revenue in R&D Solutions was $7.556 billion, growing at 31.2% reported and 30.4% at constant currency.
Full-year CSMS revenue was $784 million representing 5.8% growth on a reported basis and 5.7% at constant currency.
Adjusted EBITDA was $828 million for the fourth quarter, which was 12.7% growth on a reported basis.
Full-year adjusted EBITDA was $3.022 billion, up 26.8% year over year on a reported basis.
Fourth-quarter GAAP net income was $318 million, and GAAP diluted earnings per share was $1.63.
Full-year GAAP net income was $966 million or $4.95 of earnings per diluted share.
Adjusted net income was $496 million for the fourth quarter, up 20.7% year over year.
And adjusted diluted earnings per share grew 20.9% to $2.55.
For the full year, adjusted net income was $1.760 billion or $9.03 per share, up 41%.
R&DS backlog now stands at a record $24.8 billion, an increase of 10.2% year over year.
Full year 2021 net new bookings, including pass-throughs, rose over $10 billion for the first time.
That's 14.6% growth compared to 2020.
Cash flow from operations was $692 million, and capex was $184 million, which resulted in free cash flow of $508 million.
This brought our free cash flow for the full year to a record $2.3 billion, up 70% versus the prior year.
At December 31, cash and cash equivalents totaled $1.366 billion and gross debt was $12.125 billion, resulting in net debt of $10.759 billion.
Our net leverage ratio at December 31 was 3.56 times trailing 12-month adjusted EBITDA.
Now it's worth highlighting that our improved free cash flow over the last two years allowed us to deploy approximately $4.5 billion of capital to internal investments, acquisitions, and share repurchase, while at the same time, we were able to reduce our net leverage ratio from a high of 4.8x in Q2 2020, which you'll recall was the height of the pandemic to nearly 3.5 times.
And in doing this, we achieved our Vision '22 net leverage ratio target of 3.5 times to four times a full year early.
In the quarter, we repurchased $174 million of our shares, which resulted in full-year share repurchase of $395 million, and we ended the year with 195 million fully diluted shares outstanding and $523 million of share repurchase authorization remaining under our existing program.
Now last week, our board of directors approved a $2 billion increase to our share repurchase authorization, which increases our remaining authorization to just over $2.5 billion.
And in maintaining this guidance, we actually absorbed a $70 million revenue headwind from FX since we initially guided in November.
So, to summarize the overall guidance for the full year, we expect revenue to be between $14.700 billion and $15 billion, which represents year-over-year growth of 7.1% to 9.2% at constant currency and 6% to 8.1% on a reported basis compared to 2021.
Now we now expect adjusted EBITDA to be between $3.330 billion and $3.405 billion representing year-over-year growth of 10.2% to 12.7%.
And we also now expect adjusted diluted earnings per share to be between $9.95 and $10.25, which represents year-over-year growth of 10.2% to 13.5%.
Now our full year 2022 guidance assumes at December 31, 2021, foreign currency exchange rates remain, in fact, for the balance of the year.
Now compared to the prior year, I should mention FX is now a headwind of 110 basis points to our full-year revenue growth, and our projected revenue growth includes a little bit over 100 basis points of contribution from M&A activity.
Now with our analyst and investor conference in November, we told you to anticipate that our COVID-related revenue will step down by approximately $1 billion in 2022 but will more than compensate for that headwind with strong growth in our base business.
At the segment level, we anticipate full-year Technology and Analytics Solutions revenue growth of between 5% and 7%.
Research and Development Solutions revenue growth is expected to be between 8% and 10%.
And finally, Contract Sales and Medical Solutions revenue was anticipated to be down about 2%.
For the first quarter, our revenue is expected to be between $3.515 billion and $3.575 billion, representing growth of 4.8% to 6.6% on a constant-currency basis and 3.1% to 4.9% on a reported basis.
Adjusted EBITDA is expected to be between $800 million and $815 million, up 7.5% to 9.5%.
And finally, adjusted diluted earnings per share is expected to be between $2.40 and $2.46, growing 10.1% to 12.8%.
R&DS recorded its largest-ever quarter of service bookings and for the first time, had over $10 billion of total net new bookings in a year.
Our contracted backlog improved to a record of nearly $25 billion, up over 10% year over year.
We delivered another strong quarter of free cash flow, bringing the full year to a record $2.3 billion.
We closed 2021 with net leverage of 3.6 times trailing 12-month adjusted EBITDA.
Our board approved a $2 billion increase to our share repurchase authorization.

Summary:
Fourth-quarter adjusted diluted earnings per share of $2.55 grew 20.9%.
Fourth-quarter revenue of $3.636 billion grew 10.2% on a reported basis and 11.6% at constant currency.
Fourth-quarter GAAP net income was $318 million, and GAAP diluted earnings per share was $1.63.
And adjusted diluted earnings per share grew 20.9% to $2.55.
This brought our free cash flow for the full year to a record $2.3 billion, up 70% versus the prior year.
And in maintaining this guidance, we actually absorbed a $70 million revenue headwind from FX since we initially guided in November.
And we also now expect adjusted diluted earnings per share to be between $9.95 and $10.25, which represents year-over-year growth of 10.2% to 13.5%.
Now our full year 2022 guidance assumes at December 31, 2021, foreign currency exchange rates remain, in fact, for the balance of the year.
For the first quarter, our revenue is expected to be between $3.515 billion and $3.575 billion, representing growth of 4.8% to 6.6% on a constant-currency basis and 3.1% to 4.9% on a reported basis.
And finally, adjusted diluted earnings per share is expected to be between $2.40 and $2.46, growing 10.1% to 12.8%.