New indirect method for estimating the birth prevalence of the Apert syndrome.

An indirect method for estimating the birth prevalence of the Apert syndrome is presented. The fraction of Apert syndrome patients in large clinical surveys of all cases of craniosynostosis is calculated and the fractional component obtained is multiplied by the known birth prevalence of craniosynostosis in general. Apert syndrome makes up approximately 4% of all cases of craniosynostosis. Using a weighted average estimate, birth prevalence was calculated to be 13.7/1,000,000. The results of the indirect method compare favorably with those obtained by the direct method. Nevertheless, because the indirect method is based on a number of assumptions that are easily violated, we cannot recommend its general use except under special conditions.