False positives in universal neonatal screening for permanent childhood hearing impairment

Kennedy, C.R., Kimm, L., Thornton, A.R.D. and Davis, A. (2000) False positives in universal neonatal screening for permanent childhood hearing impairment. The Lancet, 356 (9245), 1903-1904. (doi:10.1016/S0140-6736(00)03267-0).

Abstract

High rates of false-positive neonatal screens for permanent childhood hearing impairment (PCHI) associated with raised hearing thresholds lead to unnecessary assessments of the baby, which may worry parents. False-positive rates need to be reduced, especially in view of the UK government's announcement that national neonatal screening will be introduced. We report screening criteria that give a six-fold reduction in false-positive rates.

We have reported a trial in the Wessex region of the UK, which showed that universal neonatal screening for early identification of permanent childhood hearing impairment (PCHI) is highly effective.1 Universal neonatal screening increased the yield before 6 months of age of true cases of bilateral moderate or severe PCHI by 71 per 100?000; the equivalent to four of five cases expected in the target population for screening. We have not previously reported the false-positive rate, which is the rate of screening positive in babies not affected by the target condition.

If a baby screens positive for hearing impairment (HI), follow-up tests are needed, including an estimation of hearing threshold and, if the threshold is raised, more tests and a medical assessment to find out whether or not the hearing loss is permanent. The cost of a postneonatal screening follow-up in one of the centres in the Wessex trial was £5540 per 1000 patients in the target population each year.2 This did not include the costs to the parents such as any increase in anxiety.

We report the yield of true cases, positive predictive value, false-alarm rate, and raised hearing threshold rate in 158 babies who screened positive from 12?523 babies screened during the second half of the Wessex trial. We also report, in the same population, the effect of increasing the threshold for screening positive and compare these figures with data from Whipps Cross Hospital, London, UK,3 a study of transient evoked otoacoustic emissions (TEOAE)-based universal neonatal screening in the UK.

We used a two-step neonatal screen.1 First we tested for TEOAE. In infants younger than 48 h, a pass on the first step was defined as unilateral detection of TEOAE although in older babies, bilateral detection was required. Babies failing the first step proceeded, on the same day, to the second step of automated auditory-brainstem-response (AABR) testing. A positive screen was defined as unilateral failure on AABR (table 1). In the amended protocol (table 1) a positive screen was redefined, in the subgroup of babies at low risk,1 as bilateral failure on AABR testing. The Whipps Cross hospital screen (table 1) used TEOAE testing as the first and second step before and after postnatal discharge from hospital, respectively, with bilateral failure on the second occasion constituting a positive screen.

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