Some time ago, Neil Davey began pondering a question that might not consume the average teenager: How, he wondered, could he effectively detect and isolate circulating tumor cells in a cancer patient’s bloodstream?

This was more than a fleeting thought.

It stayed with him through research and an internship and finally led to Sunday in Washington, where the 18-year-old displayed his work publicly, standing among the nation’s top teenage science students as a finalist in the Intel Science Talent Search.

“The idea is that you would be able to accurately diagnose cancer at a much, much earlier stage,” Davey said as onlookers, journalists and judges milled about a hall at the National Geographic Society. The top 10 winners will be named at a gala Tuesday.

It was an exhilarating moment for the Gaithersburg teenager and for his public high school: Montgomery Blair, in Silver Spring.

Blair produced three of Intel’s 40 national finalists this year, the most in the country. And its success is more than a one-year blip: It ranks as No. 1 for finalists since 1999, when it reached its high point of six. Twenty-five more have been named since then.

“They blow everybody else out of the water; they do a great job,” said Wendy Hawkins, executive director of the Intel Foundation.

Blair’s finalists this year also included Jessica Shi, 17, of Rockville, who did research in mathematics, examining the speeds of families of intersection graphs, and Shaun Datta, 18, of Gaithersburg, who focused on physics, investigating the interaction between baryons in nuclear matter.

“We really encourage them to move beyond learning stuff to applying it and creating new knowledge,” said Peter Ostrander, coordinator of Blair’s math, science and computer science magnet program, in which the three finalists are enrolled.

The prestigious science competition — with finalists from 33 schools in 14 states — goes back to 1942 and will give more than $600,000 in awards. A program of the Society for Science & the Public, it was done for years in partnership with Westinghouse and since 1998 with Intel. Finalists this year investigated many topics, including the diagnosis and treatment of Alzheimer’s disease and potential drug candidates for treating the flu. They were culled from 300 semifinalists, including nine from Blair.

Blair’s finalists are part of a magnet program that includes specially designed courses and a research class to help students find internships and come up with areas of investigation for a senior research paper.

The three students gave credit to those experiences, as well as their Blair teachers, family encouragement and fellow students. The magnet program includes about 100 students in each high school grade.

“We spend lunch talking to each other about math or physics problems we’ve had in class, and it’s a really supportive community,” Shi said.

Shi and her fellow finalists said they were stunned to learn in January that they’d made the cut as finalists.

“It was a total surprise to me,” Datta said. “I never even really considered that.”

The success elicited a certain awe.

“They’re geniuses in the making, if not already,” said Montgomery County Board of Education member Christopher S. Barclay, whose district includes Blair.

Just the titles of the students’ work seemed beyond their years.

Datta’s, which he deemed one of the shorter ones, was: “Saturated Nuclear Matter in the Large Nc and Heavy Quark Limits of Quantum Chromodynamics.”

“I looked at their topics and I thought, ‘Wow, geez, so that’s a 17-year-old who did that?’ ” said Therese Gibson, Blair’s PTSA president. The way they talk and think, she said, “it’s like these kids already have PhDs.”

Virginia and the District did not have finalists this year. Maryland had a fourth, Benjamin Freed, a senior at Governor Thomas Johnson High School in Frederick.

Locally, Fairfax County’s Thomas Jefferson High School for Science and Technology also stands out for frequent Intel finalists, producing 24 since 1989, according to Intel. Twice it reached a high point of three finalists in one year, Intel said.

The Intel contest describes the finalists as the science innovators of the future. Davey is hoping to continue his research at Harvard, where he worked at a lab with microfluidics last summer and will attend college in the fall.

Asked whether he considers himself a scientist today, he broke the question into two parts.

The classic scientist, he said, works in a lab and has a PhD, which is not him — not yet.

But if the meaning of scientist includes those who are fond of science, with the independent, problem-solving mind of a scientist, then, he said, “I hope I am in that latter definition.”