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Sample size of studies of diagnostic accuracy in ophthalmology: literature survey
  1. Frank Bochmann (fms.bochmann{at},
  2. Zoe Johnson,
  3. Augusto Azuara-Blanco
  1. Eye Clinic, Aberdeen Royal Infirmary, United Kingdom
  2. Eye Clinic, Aberdeen Royal Infirmary, United Kingdom
  3. Eye Clinic, Aberdeen Royal Infirmary, United Kingdom


    Aims: To determine the reporting of sample sizes in studies on diagnostic accuracy in ophthalmology.

    Design: Literature survey.

    Data sources: Literature published in 2005

    Methods: The frequency of reporting calculations of sample sizes and the sizes of samples were extracted from the published literature. A manual search of five leading clinical journals in ophthalmology with the highest impact (Investigative Ophthalmology and Visual Science, Ophthalmology, Archives of Ophthalmology, American Journal of Ophthalmology, and British Journal of Ophthalmology) was conducted by two independent investigators.

    Results: A total of 1698 articles were identified, of which 40 studies were on diagnostic accuracy. One study reported that sample size was calculated prior to initiating the study. Another study reported considerations of sample size without calculation. The mean (+/- standard deviation) sample size of all diagnostic studies was 172.6 (+/-218.9). The median prevalence of the target condition was 50.5%.

    Conclusion: Only a small minority of studies consider sample size in their methodology. Inadequate sample sizes in diagnostic accuracy studies may result in misleading estimates of test accuracy. An improvement in current standards on the design and reporting of diagnostic studies is warranted.

    • accuracy of diagnostic tests

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