Vision screening in New Zealand: an audit of the B4 School Check.

AIMS: To assess the accuracy of the B4 School Check (B4SC) vision screening programme in two distinct regions of New Zealand.

METHODS: A retrospective audit of all children who were screened for vision in the Southern and Tairawhiti District Health Boards, between 1 April and 30 September 2016. Results from the B4SC screening programme (n=2,109) were compared to records for all children who were screened and subsequently presented to an optometrist at a DHB eye clinic (n=116).

RESULTS: The B4SC produced a sensitivity in the range of 54.7% to 94.7% and a specificity of 93.8% to 95.7%. There was a low positive predictive value (PPV), between 29.5% and 51.1%, with a relatively high number of false positive referrals. The negative predictive value (NPV) was higher, however, between 97.8% and 99.7%, meaning nearly all children who passed screening had no visual impairment.

CONCLUSIONS: The high NPV is reassuring that very few children with visual impairment are missed by screening. The low PPV was consistent with the international literature and is related to a tendency for over-referral from the B4CS programme. Further work could evaluate increasing the threshold for referral to reduce the number of false positive cases.