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H.R. Wright, J.E. Keeffe, H.R. Taylor; A More Detailed Grading System May Help Explain the Poor Correlation Between PCR and Clinical Diagnosis of Trachoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4728.
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Individuals who are PCR positive for Chlamydia trachomatis without clinical signs according to the simplified WHO system may have clinical signs of trachoma according to the more detailed standard WHO system. A set of photographs was assessed to evaluate the benefit of using a more detailed system to grade trachoma within the research setting.
The left eyes of 395 children living in two remote Aboriginal communities in Australia were photographed. Eyes was graded at the time of examination according to the simplified WHO system. Photographs were subsequently graded for the presence of trachomatous inflammation follicular (TF) and trachomatous inflammation intense (TI) according to the simplified WHO system. Each photo was then graded for follicles (F0– 3) and upper tarsal hypertrophy (P0– 3) using the standard WHO system. F2 and F3 compare to TF, and P3 to TI but F1, P1 and P2 are considered normal by the simplified WHO system. Agreement between clinical grading and photo grading, and agreement between the two grading systems was examined using kappa statistics. The number of individuals identified as having signs of trachoma by the standard WHO system, but who were considered normal using the simplified WHO system was determined.
Of the 395 children examined and photographed, 368 (93.2%) had gradable photos. The prevalence of TF was 21.7% and TI was 1.3% according to clinical grading. Photo grading had excellent agreement with clinical grading using the simplified WHO system; the prevalence of TF was 22.6% (kappa 0.88) and TI was 1.9% (kappa 0.83). Furthermore, photo grading with the standard WHO system agreed with photo grading using the simplified WHO system; the prevalence of F2 or F3 was 22.6% (kappa 0.98) and P3 was 2.4% (kappa 0.87). The standard WHO grading system identified an additional 25.3% of the total population who had signs of trachoma but did not have TF or TI.
There is excellent agreement between the two main trachoma grading systems. This allows comparison to be made between studies using the different systems with a high degree of confidence. Furthermore, by utilising the more detailed standard WHO grading system in research, individuals with PCR evidence of infection but without TF or TI may be identified as having clinical signs of trachoma.
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