Glenn A. Eisenberg
Executive Vice President and Chief Financial Officer at Laboratory Co. of America
Thank you, Adam. I'm going to start my comments with a review of our first quarter results, followed by a discussion of our performance in each segment and conclude with an update on our full year guidance. For reference, we've also included additional business information that can be found in our supplemental deck on our Investor Relations website. Revenue for the quarter was $3.2 billion, an increase of 4.6% compared to last year primarily due to organic base business growth and the impact from acquisitions, partially offset by lower COVID testing.
The base business grew 6.7% compared to the base business last year, while COVID testing revenue was down 70%. Organically, in constant currency, the base business grew 4.3%. Operating income for the quarter was $321 million, 10.1% of revenue or 14.3% on an adjusted basis. During the quarter, we had $49 million of restructuring charges and special items, primarily related to acquisitions and LaunchPad initiatives. In addition, we had $22 million of expense for transition service agreements related to the spin Fortrea, with corresponding income recorded in other income.
Excluding these items and amortization of $60 million, adjusted operating income in the quarter was $453 million or 14.3% of revenue compared to $448 million or 14.7% last year. The margin decline was due to lower COVID testing. Base business margins were up as the benefit demand and LaunchPad savings were partially offset by higher personnel costs. Our LaunchPad continues to be on track to deliver $100 million to $125 million of savings this year, consistent with our long-term target.
The adjusted tax rate for the quarter was 23% compared to 22.1% last year. The higher adjusted tax rate was primarily due to a stock-based compensation benefit in the prior year. We continue to expect the full year adjusted tax rate to be approximately 23%. Net earnings from continuing operations for the quarter were $228 million or $2.69 per diluted share.
Adjusted EPS were $3.68 in the quarter, up 7% from last year. Operating cash flow from continuing operations was a use of $30 million in the quarter compared to $186 million generated a year ago. The reduction in cash flow was due to lower cash earnings, primarily related to deferred taxes and the timing of working capital requirements. Capital expenditures totaled $134 million in the quarter or 4.2% of revenue. This compares to $78 million or 2.6% in the prior year, which was impacted by the then pending spin Fortrea. For the full year, we continue to expect capital expenditures to be approximately 3.5% of revenue.
Free cash flow from continuing operations for the quarter was a use of $164 million. The first quarter is seasonally the company's lowest quarter for free cash flow. We continue to expect free cash flow for the full year to be between $1 billion to $1.15 billion. During the quarter, the company invested $259 million in acquisitions and paid out $62 million in dividends. At quarter end, we had $99 million in cash, while debt was $5.1 billion. Our leverage was 2.5 times gross debt to trailing 12 months adjusted EBITDA.
Now I'll review our segment performance, beginning with Diagnostics Laboratories. Revenue for the quarter was $2.5 billion, an increase of 4.1% compared to last year, with organic growth of 1.8% and acquisitions net of contributing 2.2%. The base business grew 6.8% compared to the base business last year, while COVID testing revenue was down 70%. Organically, in constant currency, the base business grew 4.4%. Total volume increased 3.4% compared to last year.
Base business volume grew 4.9% compared to the base business last year as organic volume increased 2.7%, while acquisitions contributed 2.2%. Price/mix increased 0.6% versus last year due to an organic base business increase that's partially offset by lower COVID testing. Base business organic price/mix was up 1.7% compared to the base business last year. Diagnostics adjusted operating income for the quarter was $418 million or 16.9% of revenue compared to $442 million or 18.5% last year.
The decrease in adjusted operating income was due to a reduction in COVID testing, while base business income was up as the benefit of demand and LaunchPad savings were partially offset by higher personnel costs. The decrease in adjusted operating income margin was due to a reduction in COVID testing, the negative impact from weather and the mix impact from lab management agreements, which we expect to improve over time.
Now I'll review the segment performance of biopharma laboratory services. Revenue for the quarter was $711 million, an increase of 7.5% compared to last year due to increase in organic revenue of 5.1% and foreign currency translation of 2.4%. The revenue growth was driven by continued strength in Central Labs, which was up 13%, while early development was down 4% due to continued higher-than-normal cancellations and lower orders. While cancellations are higher than normal, we have seen a sequential improvement from last quarter.
Biopharma adjusted operating income for the quarter was $100 million or 14.1% of revenue compared to $74 million or 11.1% last year. Adjusted operating income and margin increased due to organic growth and LaunchPad savings, partially offset by higher personnel costs. We ended the quarter with a backlog of $7.9 billion, and we expect approximately $2.5 billion of this backlog to convert into revenue over the next 12 months. The trailing 12 months book-to-bill was 1.00, which we expect to increase throughout the year.
Now I'll discuss our updated 2024 full year guidance, which assumes foreign exchange rates effective as of March 31, 2024, for the remainder of the year. The enterprise guidance also includes the impact from currently anticipated capital allocation, with free cash flow targeted for acquisitions, share repurchases and dividends. We expect Enterprise revenue to grow 4.8% to 6.4% compared to 2023. Compared to prior guidance, this is a narrowing of the range with the same midpoint despite a 50 basis point headwind from currency.
We continue to perform well in diagnostics and are narrowing the full year guidance range and increasing the midpoint. We expect Diagnostics revenue to be up 4.8% to 6% compared to 2023. This is an increase at the midpoint from our prior guidance of 140 basis points, primarily due to stronger base business demand as well as acquisition revenue that is now forecasted in this segment, where it was previously only included in the enterprise guidance prior to the closing of the transactions.
We expect biopharma revenue to grow 3.7% to 5.7% compared to 2023. The decrease at the midpoint from our prior guidance of 180 basis points is due to currency. This includes the year-over-year positive from foreign currency translation of 40 basis points versus 220 basis points in the prior guidance. An improvement in the outlook for Central Labs is expected to be offset by early development.
We continue to expect margins in Diagnostics and Biopharma to be up in 2024 versus 2023, driven by top line growth and LaunchPad savings. Our guidance range for adjusted EPS is $14.45 to $15.35. We have narrowed the range and increased the midpoint of guidance by $0.05, driven by improvement in Diagnostics, partially offset by the change in currency. The free cash flow guidance range is $1 billion to $1.15 billion, unchanged from prior guidance. In summary, we expect to drive continued profitable growth and strong free cash flow generation that will be used for acquisitions that support our strategy and supplement our organic growth while also returning capital to shareholders through our share repurchase program and dividends.
Operator, we will now take questions.