Our team delivered another outstanding results in our third quarter with over 20% core revenue growth, nearly 40% adjusted earnings-per-share growth and strong free cash flow generation.
Our sales were $7.2 billion and we delivered 20.5% core revenue growth with portfoliowide strength led by Diagnostics and Life Sciences.
Geographically, high growth markets grew approximately 25% and developed markets were up nearly 20%.
In fact, revenue in each of our three largest markets, North America, Western Europe and China was up approximately 20% or more in the quarter.
Our gross profit margin increased by 550 basis points to 60.3% primarily due to higher sales volume, the favorable impact of higher margin product mix, and the impact of prior-year purchase accounting adjustments related to the Cytiva acquisition that did not repeat in 2021.
Now, adjusted diluted net earnings per common share were $2.39 and were up 39% compared to 2020 and we generated $1.7 billion of free cash flow in the quarter, bringing our year-to-date total to $5.2 billion, which is up 46.5% year-over-year.
We continue to accelerate organic growth investments across the entire portfolio and increased our research and development spend by approximately 30% year-over-year.
In fact, recently launched products like the SCIEX Zeno 7600 and the Triple Quad 7500 and Beckman Life Sciences' CytoFLEX SRT benchtop cell sorter are just a few great examples of how we're driving market share gains through proprietary innovation and enhancing our growth trajectory going forward.
And we expect our total capital expenditures across Danaher to be approximately $1.5 billion in 2021 as we continue to invest in support of our customers' needs today and well into the future.
Life Sciences reported revenue increased 24.5% with core revenue up 20%.
Now these strong results were led by continued demand for our bioprocessing solutions as in Cytiva bioprocessing and Pall Biotech, both grew more than 30% in the quarter, including low double-digits non-COVID related core growth.
COVID-related vaccine and therapeutic revenue contributed -- continued to be strong and now exceeds $1.5 billion year-to-date.
Cytiva also added more than 1,500 new associates to the global team since joining Danaher to help ensure that we're supporting our customers today and continue meeting their needs well into the future.
In Diagnostics, reported revenue was up 29.5% and core revenue grew 28.5% led by more than 60% growth at Cepheid.
In respiratory testing at Cepheid, we further expanded manufacturing capacity, which enabled the team to produce and ship approximately 16 million cartridges during the quarter.
COVID-only tests accounted for approximately 80% of those shipments and our 4-in-1 combination tests for COVID-19 Flu-A and B and RSV represented approximately 20%.
And we believe the team's thoughtful placement of the GeneXpert and Infinity Systems over the last 18 months is setting up Cepheid very well for future growth opportunities.
Reported revenue was up 7% with core revenue up 7.5%.
We continue to expect about $2 billion of COVID-related vaccine and therapeutic revenue in 2021.
And since we spoke at our Investor Day, we now expect to enter 2022 with approximately $2 billion in COVID-related backlog versus our previous expectation of $1.5 billion of backlog.
As I mentioned earlier, we shipped approximately 16 million respiratory tests during the third quarter and we now expect to ship approximately 55 million tests in 2021 versus our prior expectation of 50 million.
In preparation, their preference is for our 4-in-1 combination test, so we're seeing an uptick in demand for those cartridges, particularly given the recent outbreaks of RSV across the U.S. Cepheid's 4-in-1 test was also recently approved with a third gene target for SARS-CoV-2 detection, ensuring it can continue to accurately detect future COVID-19 viral mutations and reinforcing Cepheid's competitive advantage in the respiratory testing market.
We expect to deliver fourth quarter core revenue growth in the low to mid teens range, with high single-digit core revenue growth in our base business and a mid to high single-digit core growth contribution from COVID-related revenue tailwind.
Additionally, we expect to generate operating profit fall through of approximately 40% in the fourth quarter, a similar level to what we achieved in the third quarter.
Now for the full year 2021, we now expect to deliver more than 20% core tailwind and our base business will each contribute more than 10% to our 2021 core revenue growth rate.

Summary:
Our team delivered another outstanding results in our third quarter with over 20% core revenue growth, nearly 40% adjusted earnings-per-share growth and strong free cash flow generation.
Geographically, high growth markets grew approximately 25% and developed markets were up nearly 20%.
In fact, revenue in each of our three largest markets, North America, Western Europe and China was up approximately 20% or more in the quarter.
Now, adjusted diluted net earnings per common share were $2.39 and were up 39% compared to 2020 and we generated $1.7 billion of free cash flow in the quarter, bringing our year-to-date total to $5.2 billion, which is up 46.5% year-over-year.
Life Sciences reported revenue increased 24.5% with core revenue up 20%.
COVID-only tests accounted for approximately 80% of those shipments and our 4-in-1 combination tests for COVID-19 Flu-A and B and RSV represented approximately 20%.
Reported revenue was up 7% with core revenue up 7.5%.
We expect to deliver fourth quarter core revenue growth in the low to mid teens range, with high single-digit core revenue growth in our base business and a mid to high single-digit core growth contribution from COVID-related revenue tailwind.
Now for the full year 2021, we now expect to deliver more than 20% core tailwind and our base business will each contribute more than 10% to our 2021 core revenue growth rate.