Authors' response-Approach to evaluating the reliability and validity of conjunctival ultraviolet autofluorescence measurement

Lions Eye Institute, Centre for Ophthalmology and Visual Science, University of Western Australia, 2 Verdun St, Nedlands, 6009 Western Australia, Australia
The British journal of ophthalmology (Impact Factor: 2.98). 06/2012; 96(9):1271. DOI: 10.1136/bjophthalmol-2012-302135
Source: PubMed
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    ABSTRACT: L. I. Lin [Biometrics 45, No. 1, 255-268 (1989; Zbl 0715.62114)] objected to the use of the intraclass correlation coefficient as a way to evaluate the reproducibility of measurements between two trials of an assay or instrument and developed an alternative called the concordance correlation coefficient. It is noted that intraclass correlation refers not to a single coefficient but to a group of coefficients and that Lin’s alternative is nearly identical to a subset of the coefficients in this group.
    Biometrics 12/1997; 53(4). DOI:10.2307/2533516 · 1.57 Impact Factor
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    ABSTRACT: The CCC macro is presented for computation of the concordance correlation coefficient (CCC), a common measure of reproducibility. The macro has been produced in both SAS and R, and a detailed presentation of the macro input and output for the SAS program is included. The macro provides estimation of three versions of the CCC, as presented by Lin [L.I.-K. Lin, A concordance correlation coefficient to evaluate reproducibility, Biometrics 45 (1989) 255-268], Barnhart et al. [H.X. Barnhart, J.L. Haber, J.L. Song, Overall concordance correlation coefficient for evaluating agreement among multiple observers, Biometrics 58 (2002) 1020-1027], and Williamson et al. [J.M. Williamson, S.B. Crawford, H.M. Lin, Resampling dependent concordance correlation coefficients, J. Biopharm. Stat. 17 (2007) 685-696]. It also provides bootstrap confidence intervals for the CCC, as well as for the difference in CCCs for both independent and dependent samples. The macro is designed for balanced data only. Detailed explanation of the involved computations and macro variable definitions are provided in the text. Two biomedical examples are included to illustrate that the macro can be easily implemented.
    Computer Methods and Programs in Biomedicine 11/2007; 88(1):62-74. DOI:10.1016/j.cmpb.2007.07.003 · 1.90 Impact Factor
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    ABSTRACT: Conjunctival ultraviolet autofluorescence (UVAF) photography was developed to detect and characterise pre-clinical sunlight-induced UV damage. The reliability of this measurement and its relationship to outdoor activity are currently unknown. 599 people aged 16-85 years in the cross-sectional Norfolk Island Eye Study were included in the validation study. 196 UVAF individual photographs (49 people) and 60 UVAF photographs (15 people) of Norfolk Island Eye Study participants were used for intra- and inter-observer reliability assessment, respectively. Conjunctival UVAF was measured using UV photography. UVAF area was calculated using computerised methods by one grader on two occasions (intra-observer analysis) or two graders (inter-observer analysis). Outdoor activity category, during summer and winter separately, was determined with a UV questionnaire. Total UVAF equalled the area measured in four conjunctival areas (nasal/temporal conjunctiva of right and left eyes). Intra-observer (ρ_c=0.988, 95% CI 0.967 to 0.996, p<0.001), and inter-observer concordance correlation coefficients (ρ_c=0.924, 95% CI 0.870 to 0.956, p<0.001) of total UVAF exceeded 0.900. When grouped according to 10 mm(2) total UVAF increments, intra- and inter-observer reliability was very good (κ=0.81) and good (κ=0.71), respectively. Increasing time outdoors was strongly with increasing total UVAF in summer and winter (p(trend) <0.001). Intra- and inter-observer reliability of conjunctival UVAF is high. In this population, UVAF correlates strongly with the authors' survey-based assessment of time spent outdoors.
    The British journal of ophthalmology 03/2012; 96(6):801-5. DOI:10.1136/bjophthalmol-2011-301255 · 2.98 Impact Factor