Capture-recapture analysis of ascertainment by active surveillance in the British Congenital Cataract Study

Abstract

Purpose: Active surveillance has not been widely used in ophthalmologic research. The use of capture-recapture analysis to determine completeness of case ascertainment by active surveillance in a national study of congenital cataract is reported.

Methods: In 1 year in the United Kingdom, all incident diagnoses of congenital and infantile cataract were notified through independent ophthalmic and pediatric active surveillance schemes. Two-source capture-recapture analysis was applied to assess the level of ascertainment of infants (age < or = 12 months) by these two schemes.

Results: In a 12-month period, 161 infants with newly diagnosed congenital or infantile cataract were notified. Overall ascertainment was estimated to be 92% complete and was higher in the ophthalmic (85%) than in the pediatric (45%) scheme. Comparison with the number of cases expected, from disease frequency reported in existing national congenital anomaly notification systems, suggests previous underascertainment of congenital cataract in such passive reporting systems.

Conclusions: This study shows the effectiveness of two-source active surveillance in identifying a nationally representative cohort that will provide better information about this disorder than has been available from sources of routinely collected data.