Heart tests on Wellington schoolchildren have picked up four cases of previously undetected rheumatic heart disease for each known case of rheumatic fever.
The findings of the pilot study have led researchers to call for greater use of ultrasound scans to detect the serious problems being caused in children by rheumatic fever.
Community paediatrician Nikki Blair was part of the pilot project involving 620 students in Porirua East. She said people can develop the longer-term disease without having had rheumatic fever, just exposure to the bug that causes it.
Dr Blair told Radio New Zealand's Nine to Noon programme on Monday the national approach of throat-swabbing to detect rheumatic fever isn't enough.
"We need to be focusing on the wider picture, which is early detection of rheumatic heart disease, awareness that it's not all about sore throats and all about rheumatic fever."
Dr Blair said many children with rheumatic fever do not recall ever having had a sore throat, and ultrasound imaging should be used more to detect rheumatic heart disease.