UK researchers have developed a new "while you wait" test for the sexually transmitted infection chlamydia, which can provide a result within 30 minutes.
The test was found to be effective for diagnosing chlamydia
A study of 1,300 women in three clinics found the test, which uses a vaginal swab, to be cheap and effective, the British Medical Journal reported.
Currently, tests have to be sent to a laboratory, leading to delays in diagnosis and treatment.
Currently one in 10 young people in the UK tests positive for the infection.
But on-the-spot diagnosis might improve the national chlamydia screening programme, experts said.
Opportunistic screening for men and women under 25 is currently being rolled out across England.
But some of those tested do not come back to get the results or may unwittingly infect others before they are diagnosed.
Chlamydia often produces no symptoms but if left untreated can result in complications such as pelvic inflammatory disease, ectopic pregnancy, and infertility.
The new test can show a positive result in as little as 10 minutes, said researchers at the University of Cambridge.
It means women can receive the result while still at the clinic and receive treatment and start to contact sexual partners straight away.
The kit looks a bit like a pregnancy test and shows two blue lines for a positive result, one for a negative result and no line if the test has not worked.
Study leader Dr Helen Lee said: "The hands-on time is less than a minute and then you have to wait for it to develop.
"Women can do the swab themselves and they are happy with that."
She added: "In chlamydia control, the key is to screen a wider group of people and if people do not come to be tested you can take the test to them."
A US study found around 3% of women developed pelvic inflammatory disease when waiting 14 days for a test result.
Dr Lee said the test would not necessarily replace the current laboratory method but could be useful in some settings where there is poor uptake.
Penny Barber, chief executive of Brook in Birmingham, said: "What it means is someone gets their result through right away so they don't have the anxiety of waiting and if they are positive we can talk to them about telling their partner.
"From the clinic's point of view, the logistics of keeping track of a sample, sending them off to the lab, calling clients back in is all removed.
"There's a really good business case for clinics to use this - I'm hoping it will be available soon."
She added she couldn't see any reason why women could not use the tests at home.