Birth prevalence studies of the Crouzon syndrome: comparison of direct and indirect methods.

An indirect method for estimating the birth prevalence of the Crouzon syndrome is presented. The fraction of Crouzon 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. Crouzon syndrome makes up approximately 4.8% of all cases of craniosynostosis. Using a weighted average estimate, birth prevalence was calculated to be 16.5/1,000,000. 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 circumstances.