The first question you'd likely ask a young adult if you were screening him or her for sexually transmitted disease (STD) would be whether he or she had been sexually active.

But new research suggests that his or her answer might not always comport with lab results.

Of 14,000 people (whose mean age was about 22 years) included in astudy published this morning in the journal Pediatrics, fully 10 percent of those who tested positive for one of three common STDs (Chlamydia, gonorrhea trichomoniasis) reported they hadn't had sex during the previous 12 months.

And 60 percent of that 10 percent said they'd never had sex at all.

The numbers held even after researchers controlled for such variables as gender, race, age and education. The authors acknowledge some room for error: for instance, study participants were only asked about penile/vaginal penetration, not about oral or anal sex. The timing was such that a person could have had sex during the study period but not within the 12 months before the question was asked. And there's some small possibility of false positive readings on the urine tests used to detect STDs.

Still, the authors say, the findings suggest that physicians treating teens and young adults should perhaps use lab tests to screen all those patients for STDs, as screening only those who report they've been sexually active may lead to many cases going undiagnosed and untreated -- and ready to spread to others.

Such routine screening could of course prove controversial in some circles.

Would you want your teenage or young-adult offspring screened for STDs as a matter of course? Or do you think such screening should be reserved for young people who report they've been sexually active?