April 22 (Reuters) - Laboratory operator Quest Diagnostics DGX.N beat Wall Street estimates for first-quarter profit on Tuesday, helped by robust demand for its diagnostic tests.

Demand for diagnostic checkups has grown in recent quarters as more people, especially older Americans, have sought non-urgent surgeries they had delayed.

Diagnostic service providers such as Quest and Labcorp LH.N have also benefited from deals to manage hospital labs as they seek market share gains.

"We were not expecting any real fireworks here but rather a continuation of a slow and steady performance, and at first glance that is what 1Q delivered," Leerink Partners analyst Michael Cherny said in a note.

The company's quarterly sales rose 12% from a year earlier to $2.65 billion. Analysts, on average, estimated the company to record $2.63 billion in quarterly sales, according to data compiled by LSEG.

On an adjusted basis, Quest posted a profit of $2.21 per share in the quarter ended March 31, above analysts' average estimate of $2.15 per share.

Quest maintained its annual adjusted profit forecast at $9.55 to $9.80 per share.

(Reporting by Puyaan Singh in Bengaluru; Editing by Leroy Leo)

((Puyaan.Singh@thomsonreuters.com))