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Table 2 Example of results from a crossover study reporting PD15 on the original and dose doubling (DD) scale [26]

From: The use of the mannitol test as an outcome measure in asthma intervention studies: a review and practical recommendations

Subject PD15 Results on original scale Results on DD scale (log2 transformed data)
Placebo (P) Nedocromil (N) Ratio N:P Placebo (P) Nedocromil (N) Difference (N-P)
1 188.6 379 2.01 7.559 8.566 1.007
2 36.2  ≥ 635 17.54 5.178 9.311 4.133
3 76.8 569 7.41 6.263 9.152 2.889
4  > 635  > 635 1.00 9.311 9.311 0.000
5 292.4  > 635 2.17 8.192 9.311 1.119
6 210  > 635 3.02 7.714 9.311 1.596
7 234.7  > 635 2.71 7.875 9.311 1.436
8 86.6 328.6 3.79 6.436 8.360 1.924
9 561.3  > 635 1.13 9.133 9.311 0.178
10 258.8  > 635 2.45 8.016 9.311 1.295
11 128.4 285.5 2.22 7.005 8.157 1.153
12 76.8 122.8 1.60 6.263 6.940 0.677
13 104.1 122.5 1.18 6.702 6.937 0.235
14  > 635  > 635 1.00 9.311 9.311 0.000
15 106.7  > 635 5.95 6.737 9.311 2.573
16 104.4 170.3 1.63 6.706 7.412 0.706
17 38.7 499.9 12.92 5.274 8.965 3.691
18 223.2  > 635 2.84 7.802 9.311 1.508
19 124.2 368.9 2.97 6.957 8.527 1.571
20 100.2 172.8 1.72 6.647 7.433 0.786
21 24.8 122.8 4.95 4.632 6.940 2.308
22 142.2 554.5 3.90 7.152 9.115 1.963
23 630.4  > 635 1.01 9.300 9.311 0.010
24 401.9  > 635 1.58 8.651 9.311 0.660
Geometric Mean 155.8 409.1 2.63 7.284 8.676 1.392
(95% CI) (107.0–227.1) (317.7–526.9) (2.56–2.69) (6.741–7.827) (8.311–9.041) (1.357–1.428)
  1. Negative tests (PD15 > 635 mg) have a PD15 value of 635 mg imputed for use in calculations
  2. CI confidence interval, DD dose doubling, PD15 provoking dose at 15% drop in FEV1