Reliable statistics on the frequency of a given disease are dependent on two factors: study of large groups of individuals, accuracy of diagnosis. Students of such a problem may compile their statistics from critical analysis of the literature and from their own personal observations. In these personal observations accuracy of diagnosis can be obtained only by careful methods of investigation, both clinical and laboratory; the clinical including an inquiry into the family and personal history of the individual and the practice of making a physical examination; the laboratory including the usual routine tests and, in addition, any methods specially applicable to the subject under discussion.
In accordance with this general plan, we have made an inquiry as to the incidence of hereditary syphilis, drawing our final conclusions from an analysis of the literature and an intensive study on our own part of 695 patients at The Children's Memorial Hospital.
CHURCHILL FS, AUSTIN RS. FREQUENCY OF HEREDITARY SYPHILIS. Am J Dis Child. 1916;XII(4):355-363. doi:10.1001/archpedi.1916.04110160024003