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Chaiyaporn Vatanatham, Nicholas J Jackson, Judy L. Chen, Gary N Holland, Edmund Tsui; Comparison of various statistical methods for calculating laser flare photometry values in patients with uveitis. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1408.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate various statistical methods of calculating laser flare photometry (LFP) values in patients with uveitis. The currently accepted approach to calculating LFP values is to obtain 7 measurements, delete the highest and lowest values, and use the mean of the 5 remaining values to reflect the level of anterior chamber (AC) flare.
Patients with a history of uveitis were prospectively enrolled and underwent comprehensive eye examinations and grading of AC flare with a modified Standardization of Uveitis Nomenclature (SUN) grading system, which included Grade 0.5+. Seven repeat LFP measurements were obtained on both the Kowa FM-500 (used originally to establish the current approach) and FM-700 laser flare meters during a single visit. Eight statistical methods were utilized to compare LFP measurements, including: 1) comparison of raw data; 2) mean of raw data; 3) mean after removal of highest and lowest values; 4) median of raw data; 5) Median Absolute Deviation (MAD) outlier detection with mean (high threshold of 2.24); 6) MAD outlier detection with mean (low threshold of 1.28); 7) boxplot outlier detection (Carling method) with mean; and 8) boxplot outlier detection (Tukey method) with mean. LFP values were also compared with the SUN grading system. Agreement between the FM-500 and FM-700 was characterized using intraclass correlation coefficients (ICC).
LFP was performed on 126 eyes (64 patients, mean age 42.3±22.7 years, 45/64 [70.3%] female). Distribution of AC flare SUN grades were Grade 0 (n=48 eyes), 0.5+ (6), 1+ (28), 2+ (16), 3+ (6), 4+ (2). Mean LFP values for each grade were: Grade 0 (mean=10.2, range [0, 98]), 0.5+ (19.5, [0, 41.9]), 1+ (16.4, [1.8, 359]), 2+ (24.6, [0, 100.9]), 3+ (135.0, [5.7, 325.5]), 4+ (166.4, [69.3, 377.5]). Mean LFP values (photon units/msec) on the FM-700 across the 8 methods were 23.33, 23.71, 21.08, 22.88, 22.90, 22.81, 22.83, 22.92, respectively. Across all 8 methods, the ICC for LFP values between the two flare meters did not vary substantially, with a range of ICC from 0.81 to 0.84. LFP values correlated with SUN grades (correlation coefficients 0.68-0.72 across all 8 methods, all p<0.001).
All eight statistical methods for calculating LFP values resulted in similar flare values compared to the current standard, suggesting that alternative, simpler methods of calculating LFP values may be suitable.
This is a 2021 ARVO Annual Meeting abstract.
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