Obstacles to timely neonatal screening in North Thames

To assess the timeliness of neonatal (Guthrie card) screening in North Thames, and to identify the most effective ways of improving it.

Analysis of information routinely collected in the course of neonatal screening; reanalysis of published data on blood phenylalanine concentration in phenylketonuria (PKU) over the first two weeks; simulation studies on the impact of different interventions.

100,690 infants born over one year and screened at Great Ormond Street Hospital NHS Trust.

Interval between birth and reading PKU screen results.

Although 75% of samples (district range 55-91%) were collected by day 7, only 81% had arrived in the laboratory seven days later (range 57-96%). The average interval between birth and reading results was 14.5 days, with only 9.7% read by day 10. Samples could be collected from day 4 without significant impact on false negative rates for PKU. If samples were collected from day 4 and posted promptly (second class), the average interval between birth and reading results could be reduced to 9.3 days. If first class mail were used and the laboratory operated on Saturdays, and used assays that could be read the same day rather than bacterial inhibition assays, the average would be 7.8 days, with 96% read by day 10.

Timeliness of neonatal screening shows unacceptable variation between districts, and delays in dispatch of specimens to the laboratory. Same day, first class posting should be introduced, and samples could be collected between days 4 and 8.