Net sales for the first quarter of 2021 were $726.8 million, which is a 27.1% increase on a reported basis versus $571.6 million in Q1 of 2020.
On a currency-neutral basis, sales increased 23.4%.
The first quarter year-over-year revenue growth was impacted by a tough compare of about $10 million revenue carryover to Q1 of 2020 related to the December 2019 cyber-attack.
Generally, we are seeing most academic and diagnostic labs now running about 90% capacity, which is an improvement to what we saw in Q4.
We estimate that COVID-19-related sales were about $94 million in the quarter.
Sales of the Life Science Group in the first quarter of 2021 were $366.5 million compared to $227.2 million in Q1 of 2020, which is a 61.3% increase on a reported basis, and a 56.9% increase on a currency-neutral basis.
Excluding Process Media sales, the underlying Life Science business grew 56.2% on a currency-neutral basis versus Q1 of 2020.
Sales of the Clinical Diagnostics Group in the first quarter were $358.5 million, compared to $340.3 million in Q1 of 2020, which is a 5.4% growth on a reported basis, and a 2.2% growth on a currency-neutral basis.
We started to see a recovery of market demand for non-COVID business, with diagnostics labs returning to about 90% of pre-COVID levels.
The reported gross margin for the first quarter of 2021 was 55.1% on a GAAP basis, and compares to 55.5% in Q1 of 2020.
Amortization related to prior acquisitions recorded in cost of goods sold was $4.6 million compared to $3.9 million in Q1 of 2020.
SG&A expenses for Q1 of 2021 were $225.9 million or 31.1% of sales compared to $193.7 million or 33.9% in Q1 of 2020.
The year-over-year SG&A expenses increased mainly due to expenses associated with the restructuring initiative and higher employee-related expenses, and it was offset slightly by a $5 million cybersecurity insurance settlement related to the 2019 cyber-attack as well as lower discretionary spend.
Total amortization expense related to acquisitions recorded in SG&A for the quarter was $2.4 million versus $2 million in Q1 of 2020.
Research and development expense in Q1 was $73.9 million or 10.2% of sales compared to $49.3 million or 8.6% in Q1 of 2020.
Q1 operating income was $100.9 million or 13.9% of sales compared to $74.4 million or 13% in Q1 of 2020.
The change in fair market value of equity securities holdings added $1.179 billion of income to the reported results, which is substantially related to holdings of the shares of Sartorius AG.
During the quarter, interest and other income resulted in net other income of $16.9 million compared to $3.3 million of expense last year.
Q1 of 2021 included $19 million of dividend income from Sartorius, which was declared this year in Q1.
The effective tax rate for the quarter was 24.7% compared to 23.7% in Q1 of 2020.
Reported net income for the first quarter was $977.4 million, and diluted earnings per share were $32.38.
In cost of goods sold, we have excluded $4.6 million of amortization of purchased intangibles, $24 million of restructuring-related expenses and a small legal reserve benefit.
These exclusions moved the gross margin for the first quarter of 2021 to a non-GAAP gross margin of 59% versus 55.9% in Q1 of 2020.
Non-GAAP SG&A in the first quarter of 2021 was 25.4% versus 33.3% in Q1 of 2020.
In SG&A, on a non-GAAP basis, we have excluded restructuring-related expenses of $34.7 million, legal-related expenses of $4.4 million, and amortization of purchased intangibles of $2.4 million.
In R&D, we have excluded $16.9 million of restructuring-related expenses.
The non-GAAP R&D expense in Q1 was consequently 7.9%.
The cumulative sum of these non-GAAP adjustments result in moving the quarterly operating margin from 13.9% on a GAAP basis to 25.8% on a non-GAAP basis.
This non-GAAP operating margin compares to a non-GAAP operating margin in Q1 of 2020 of 13.9%.
We have also excluded certain items below the operating line, which are the increasing value of the Sartorius equity holdings of $1.179 billion, and $1.8 million of loss associated with venture investments.
Our non-GAAP effective tax rate for the quarter was 23.6% versus 25.7% in Q1 of 2020.
And finally, non-GAAP net income for the first quarter of 2021 was $157.4 million, or $5.21 diluted earnings per share compared to $57.6 million and $1.91 per share in Q1 of 2020.
Total cash and short-term investments at the end of Q1 were $1.025 billion, compared to $997 million at the end of 2020.
During the first quarter, we purchased 89,506 shares of our stock for a total of $50 million at an average price of approximately $559 per share.
For the first quarter of 2021, net cash generated from operations was $114 million, which compares to $63 million in Q1 of 2020.
The adjusted EBITDA for the fourth quarter of 2021 was $232 million or 31.9% of sales, and excluding the Sartorius dividend, was 29.3%.
The adjusted EBITDA in Q1 of 2020 was $107.4 million or 18.8% of sales, which did not include the 2020 Sartorius dividend.
Net capital expenditures for the first quarter of 2021 were $19.5 million, and depreciation and amortization for the first quarter was $32.7 million.
We began the year with a projection of between 4.5% and 5% non-GAAP sales growth, and a non-GAAP operating margin of between 16% and 16.5%.
Even though we continue to be uncertain about the duration and impact of the COVID-19 pandemic, given the results of the first quarter and our current outlook, we are now guiding currency-neutral revenue growth in 2021 to be between 5.5% and 6%.
This includes COVID-related sales, which we estimate to be between $170 million and $180 million versus our prior estimate of about $150 million and $160 million.
Full year non-GAAP gross margin is now projected between 56.5% and 57% versus our previous guidance of 56.2% and 56.5%.
And full year non-GAAP operating margin to be about 17%, and full year adjusted EBITDA margin to be about 22% versus previous guidance of 21%.

Summary:
Net sales for the first quarter of 2021 were $726.8 million, which is a 27.1% increase on a reported basis versus $571.6 million in Q1 of 2020.
Reported net income for the first quarter was $977.4 million, and diluted earnings per share were $32.38.
And finally, non-GAAP net income for the first quarter of 2021 was $157.4 million, or $5.21 diluted earnings per share compared to $57.6 million and $1.91 per share in Q1 of 2020.
Even though we continue to be uncertain about the duration and impact of the COVID-19 pandemic, given the results of the first quarter and our current outlook, we are now guiding currency-neutral revenue growth in 2021 to be between 5.5% and 6%.