Accuracy and implications of a reported family history of glaucoma - Experience from the glaucoma inheritance study in Tasmania

Objectives: To ascertain the prevalence of previously undiagnosed primary o pen-angle glaucoma (POAG) within 5 large POAG pedigrees and to evaluate the reliability of a reported family history of glaucoma within these pedigree s. Methods: The Glaucoma Inheritance Study in Tasmania (GIST) identified sever al large adult POAG pedigrees. Intraocular pressure (IOP), optic disc stere ophotography, and automated perimetry were performed on all adult pedigree members. Participants were classified as normal (IOP <22 mm Hg and normal o ptic disc and field); glaucoma suspect (normal field, but an IOP greater th an or equal to 22 mm Hg and/or suspicious optic disc); or POAG (field defec t and glaucomatous optic disc). Some individuals with POAG had been previou sly diagnosed by their local ophthalmologist; others were diagnosed as a re sult of the GIST project. Family members with a prior diagnosis of POAG wer e asked to report if they were aware of any relatives with POAG. This repor ted family history was then directly compared with the actual pedigree (bef ore the diagnosis of new cases) to calculate agreement. Main Outcome Measure: The rate of glaucoma in pedigrees and percentage of p reviously diagnosed glaucoma cases who were aware of the positive family hi story of POAG. Results: Four hundred forty-two subjects (mean age, 54 years [range, 13-97 years]) from 5 pedigrees were examined: 316 subjects (71%) were normal, 47 (11%) were previously diagnosed with POAG, and 8 (2%) were previously diagn osed glaucoma suspects; 30 cases (7%) of POAG and 41 suspects (9%) were new ly diagnosed as a direct result of the GIST examination. Of the 47 previous ly diagnosed POAG cases, 41 were questioned about their prior knowledge of any family history and 11 (27%) were unaware of their family history of POA G. Conclusions: Examination of all adult subjects from POAG families yields ne w cases. Even in large POAG pedigrees, 27% of previously diagnosed POAG pat ients were unaware of their positive family history. These findings suggest that a higher percentage of adult POAG may be inherited than hitherto repo rted.