Quest Diagnostics Inc. said Wednesday its profit fell 16 percent in the second quarter, and the company lowered its full-year guidance. The medical laboratory operator also announced plans to trim costs and lay off 500 workers to improve profitability.

Quest's net income declined to $163.1 million, or $1.02 per share, from $194.7 million, or $1.07 per share, a year ago. Excluding costs related to its acquisitions of Celera Corp. and Athena Diagnostics, the company said it earned $1.12 per share. Revenue grew 1.5 percent, to $1.9 billion from $1.87 billion.

Analysts expected Quest to report a profit of $1.12 per share and revenue of $1.92 billion, according to estimates compiled by FactSet.

Shares of the company slipped $1.54, or 2.6 percent.

The company plans to eliminate $500 million in annual costs over the next three years. In the third quarter, it will take $12 million in after-tax charges related to staff reductions. Quest currently employs about 42,000 workers, according to FactSet. The company said the job cuts will be spread across many business units and locations.

Quest now expects an adjusted profit of $4.25 to $4.35 per share this year, down from a previous estimate of $4.25 to $4.45 per share. It said revenue will grow by about 1.5 percent rather than 2 percent. The new forecast implies about $7.48 billion in total revenue, down from $7.52 billion.

Analysts expect a profit of $4.32 per share and $7.57 billion in revenue, on average.

Quest bought Athena for $740 million in April from Thermo Fisher Scientific Inc. Athena Diagnostics makes diagnostic tests for neurological conditions. In May, Quest completed the $671 million acquisition of Celera, which focuses on sequencing the human genome and identifying links between genetic variations and disease states.

Quest said its revenue for the second quarter would have decreased by about 1 percent if not for the Celera and Athena Diagnostics deals. Clinical testing volume, or the number of requests for tests, fell 0.9 percent, while revenue per request grew 1.6 percent. Meanwhile, operating costs and expenses rose 5 percent to $1.59 billion.