Outcome of very preterm birth: children reviewed with ease at 2 years differ from those followed up with difficulty

摘要

AIM—To determine whether those most easilyreviewed in a population prevalence study differ from those followed uponly with difficulty.
METHODS—All babies born before 32 weeks ofgestation in the North of England in 1983, 1990, and 1991 were traced,and all the survivors assessed at two years by one of two independent clinicians.
RESULTS—818 of the 1138 live born babies survivedto discharge. There was some non-significant, excess disability in the5% of long term survivors who were difficult to trace because ofsocial mobility, but eight times as much severe disability in the 1%(9/796) in care and in the 5% (38/796) whose parents initially failedto keep a series of home or hospital appointments for interview, andfive times as much emergent disability in the 2.7% (22/818) who diedafter discharge but before their second birthday. Had the babies whowere seen without difficulty been considered representative of all thebabies surviving to discharge, the reported disability rate would havebeen two thirds what it really was (6.9% instead of 11.0%).
CONCLUSIONS—Population prevalence studiesthat ignore those who seem reluctant to cooperate risk seriousascertainment bias.