Table 2.
Agreement Between Test–Retest Scans and Between Observed and Predicted (Converted) Values
| Test vs. Retest | Observed vs. Predicted | |||||
|---|---|---|---|---|---|---|
| Protocol O | Protocol O Validation Data | CADME Data | ||||
| No. of eyes | 187 | 56 | 37 | |||
| No. of measured pairs | 187 | 187 | 112 | 112 | 150 | 150 |
| CST, µm | Spectralis | Cirrus | Spectralis | Cirrus | Spectralis | Cirrus |
| Mean (SD) | 387 (112) | 365 (115) | 394 (135) | 372 (140) | 313 (81) | 304 (80) |
| Median (IQR) | 365 (309, 435) | 339 (284, 404) | 347 (306, 434) | 336 (283, 400) | 296 (252, 356) | 288 (243, 346) |
| Compared with CST, µm | Retest Spectralis | Retest Cirrus | Predicted Spectralisa | Predicted Cirrusb | Predicted Spectralisa | Predicted Cirrusb |
| Mean (SD) | 385 (110) | 365 (112) | 393 (132) | 372 (126) | 329 (76) | 296 (76) |
| Median (IQR) | 362 (306, 429) | 340 (286, 406) | 359 (308, 419) | 328 (289, 409) | 313 (271, 368) | 280 (239, 336) |
| Absolute difference, µm, %c | ||||||
| Min | 0, 0% | 0, 0% | 0, 0% | 0, 0% | 0, 0% | 0, 0% |
| 5th percentile | 0, 0% | 0, 0% | 2, 0% | 1, 0% | 3, 1% | 1, 0% |
| 10th percentile | 1, 0% | 1, 0% | 2, 1% | 2, 1% | 5, 1% | 2, 1% |
| 25th percentile | 2, 0% | 1, 0% | 6, 2% | 4, 1% | 11, 3% | 4, 2% |
| Mean | 10, 3% | 7, 2% | 21, 5% | 21, 6% | 16, 6% | 9, 3% |
| Median | 4, 1% | 3, 1% | 13, 4% | 9, 3% | 17, 6% | 7, 3% |
| 75th percentile | 12, 3% | 6, 2% | 20, 6% | 23, 6% | 21, 8% | 11, 3% |
| 90th percentile | 24, 6% | 14, 4% | 48, 10% | 45, 12% | 25, 10% | 16, 5% |
| 95th percentile | 35, 10% | 32, 6% | 83, 18% | 81, 18% | 27, 12% | 27, 7% |
| Max | 87, 32% | 115, 40% | 183, 49% | 193, 62% | 65, 26% | 53, 18% |
| Difference, µm, %c | ||||||
| Min | −65, −19% | −57, −19% | −143, −35% | −193, −35% | −16, −2% | −53, −18% |
| 5th percentile | −22, −6% | −12, −3% | −58, −16% | −45, −10% | −0, −0% | −27, −7% |
| 10th percentile | −12, −3% | −8, −2% | −37, −8% | −27, −5% | 4, 1% | −16, −5% |
| 25th percentile | −3, −1% | −4, −1% | −9, −2% | −9, −3% | 10, 3% | −11, −3% |
| Mean | 2, 0% | 1, 0% | −1, 0% | −1, 1% | 15, 6% | −8, −3% |
| Median | 0, 0% | −1, −0% | 4, 1% | −2, −1% | 17, 6% | −7, −2% |
| 75th percentile | 5, 1% | 2, 1% | 14, 4% | 8, 3% | 21, 8% | −3, −1% |
| 90th percentile | 18, 4% | 8, 3% | 20, 6% | 32, 9% | 25, 10% | 1, 0% |
| 95th percentile | 29, 7% | 19, 4% | 33, 8% | 60, 18% | 27, 12% | 2, 1% |
| Max | 87, 32% | 115, 40% | 183, 49% | 148, 62% | 65, 26% | 9, 5% |
| LOA d for micron differences, µm | ||||||
| 95% LOA | (−34, 34) | (−28, 28) | (−69, 69) | (−73, 73) | (−3, 33) | (−28, 10) |
| [95% confidence interval] | [(−39, −30), (30, 39)] | [(−32, −25), (25, 32)] | [(−86, −56), (56, 86)] | [(−92, −59), (59, 92)] | [(−7, 0), (30, 37)] | [(−32, −24), (7, 15)] |
| Within eye ICC | NA | NA | 0.79 | 0.82 | 0.42 | 0.23 |
| LOA d for relative differences, %c | ||||||
| 95% LOA | (−10%, 10%) | (−8%, 8%) | (−17%, 17%) | (−22%, 22%) | (−2%, 12%) | (−8%, 3%) |
| [95% confidence interval] | [(−11%, −8%), (8%, 11%)] | [(−10%, −7%), (7%, 10%)] | [(−21%, −14%), (14%, 21%)] | [(−28%, −18%), (18%, 28%)] | [(−4%, −0%), (11%, 14%)] | [(−9%, −7%), (2%, 4%)] |
| Within eye ICC | NA | NA | 0.72 | 0.84 | 0.56 | 0.15 |
Predicted Spectralis = 40.78 + 0.95 × Cirrus.
Predicted Cirrus = 1.82 + 0.94 × Spectralis.
Percent differences for test-retest comparisons were relative to the test–rest mean and percent differences between predicted and observed values were relative to the observed values. The latter were calculated as percent difference = [(predicted – observed value)/observed value]*100%.
LOA between test versus retest and observed versus predicted values in Protocol O were centered around zero (expected mean difference) whereas the LOAs between observed versus predicted values in the CADME data were centered around the sample mean differences.
ICC, intraclass correlation; NA, not available.