The Southern District Health Board says it has no way of knowing how many parents sought a second opinion on their child's hearing before more than 1500 families were contacted and offered retesting.
The Otago Daily Times asked the health board if it knew how many children with hearing problems had a delayed diagnosis due to shortcomings in its audiology service.
The Health and Disability Commissioner's director of proceedings is considering further legal action against the health board and/or the audiologist, after deputy commissioner Theo Baker found this week both breached the patient rights code because of a delay diagnosing a boy's hearing problem.
The board sent 1532 letters to parents early last year offering retesting, more than a year after it disestablished the audiologist's position.
The retesting was for children tested between 2007 and 2010. It was thought those tested earlier would have been older, and thus any problems readily apparent.
The ODT understands some parents had sought testing earlier through other channels.
In a statement, patient services medical director Richard Bunton acknowledged this was possible.
''Parents may have chosen to have their child's hearing checked through other channels, but the DHB would have no way of knowing this, unless it was mentioned when the parents were contacted offering to retest their child.
''If any parents have concerns about the testing their child received, we encourage them to contact the DHB.''
The board had apologised to two children and their parents for the failings, he said.
The board did not answer a question about whether it had tried to quantify the extent of the problem, in terms of how many people in total it affected.
The report shows the audiologist was employed by the former Otago District Health Board before the health board merger created Southern District Health Board.
The delay diagnosing the boy's moderate to profound hearing loss - he had five tests over 11 years without a diagnosis - hindered his speech, language, literacy, cognitive and social development, Ms Baker's report said.
Her report revealed the subsequent retesting of 123 children whose parents took up the offer revealed six had hearing problems (including one with significant hearing loss).
The DHB did not provide adequate supervision or peer support for the audiologist, Ms Baker's report said.
Mr Bunton reiterated assurances the service had been strengthened.
''The DHB has taken the issues relating to audiology services very seriously and has undertaken a range of measures to improve the service and to ensure any deficiencies in the level of service patients received were identified and addressed.''
