Undetected gonococcal or chlamydial infections can lead to pelvic inflammatory disease and, in the long run, to an increased risk of chronic pain, ectopic pregnancy or infertility.

A study of girls aged 15-19 by doctors in Pittsburgh, Pennsylvania, found that no fewer than 18 per cent were infected with one or both diseases, or had yet another sexually transmitted disease - trichomoniais - that can have reproductive consequences.

When the US researchers questioned the girls they found that virtually none had any inkling they had acquired an STD, and few would have undergone testing were it not for the study.

Without the treatment they received as a consequence, some would ultimately have been joining the queues at fertility clinics, or needing extra obstetrics and gynaecological resources to handle the complications of their pregnancies.

Part of the study's success (Sexually Transmitted Diseases; 28: 321-325) is attributable to the new molecular technologies that make it possible to detect the microbes using a vaginal swab.

This simple test avoids the need for skilled staff, and for vaginal examinations that can sometimes be painful and embarrassing. Indeed, the swabbing was all done by the girls themselves.

Pittsburgh is Pittsburgh and not Plymouth, Paisley or Pwllheli - so whether a similar study in the UK would yield similar findings must be a matter of speculation.

Many parents would doubtless be appalled at the thought of their young teenage daughters being screened for an STD.

That said, the findings of such a study would be, at the very least, instructive. The NHS and the individual have a common - albeit differently motivated - interest in acquiring this knowledge.