Obtaining a confident radiologic diagnosis is often difficult as the features of interstitial lung diseases often have significant overlap. Distinguishing between UIP, NSIP, and chronic fibrotic hypersensitivity pneumonitis is often difficult in clinical practice as the HRCT findings only allow a confident diagnosis 50% of the time.9 Key features for making a confident or probable diagnosis are shown here.9
Please read below for a more detailed analysis of the features associated with these diagnosis.
This table shows several HRCT features commonly seen in patients with chronic hypersensitivity pneumonitis, UIP or IPF, and NSIP. Note the significant overlap of certain features such as reticulation and ground glass opacity, and those which are not common for all 3 diseases.
| Percentages | ||||
|---|---|---|---|---|
| Characteristic | Chronic HP (n=18) | IPF (n=23) | NSIP (n=25) | p-value |
| Reticulation | 100 (36/36) | 100 (46/46) | 100 (50/50) | NA |
| GGO | 100 (36/36) | 96 (44/46) | 100 (50/50) | 0.15 |
| <25% | 36 (13/36) | 70 (32/46) | 40 (20/50) | ≤0.007 |
| 25%-50% | 36 (13/36) | 23 (11/46) | 30 (15/50) | 0.72 |
| >50% | 28 (10/36) | 7 (3/46) | 30 (15/50) | ≤0.02 |
| Consolidation | 6 (2/36) | 0 (0/46) | 4 (2/50) | 0.31 |
| Lobular areas of decreased attenuation and vascularity | 80 (29/36) | 43 (20/46) | 34 (17/50) | <0.001 |
| Class 1 | 19 (7/36) | 26 (12/46) | 26 (13/50) | 0.74 |
| Class 2 | 22 (8/36) | 13 (6/46) | 8 (4/50) | 0.17 |
| Class 3 | 39 (14/36) | 4 (2/46) | 0 (0/50) | <0.001 |
| Centrilobular nodules | 56 (20/36)a | 15 (7/46) | 14 (7/50) | <0.001 |
| Cysts | 39 (14/36) | 0 (0/46) | 12 (6/50) | <0.001 |
| Honeycombing | 64 (23/36) | 67 (31/46) | 8 (4/50) | <0.001 |
| Traction bronchiectasis | 94 (34/36) | 100 (46/46) | 100 (50/50) | 0.07 |
| Traction bronchiolectasis | 100 (36/36) | 100 (46/46) | 100 (50/50) | NA |
| Relative subpleural sparing | 11 (4/36) | 4 (2/46) | 64 (32/50)a | <0.001 |
| Zonal predominance | ||||
| Upper | 11 (4/36) | 2 (1/46) | 0 (0/50) | 0.02 |
| Lower | 31 (11/36)b | 83 (38/46) | 94 (47/50) | <0.001 |
| Random | 58 (21/36) | 15 (7/46) | 6 (3/50) | <0.001 |
| Anatomic distribution | ||||
| Peripheral | 25 (9/36) | 78 (36/46) | 72 (36/50) | <0.001 |
| Peribronchovascular | 22 (8/36) | 0 (0/46) | 0 (0/50) | <0.001 |
| Peripheral and peribronchovascular | 17 (6/36) | 9 (4/46) | 10 (5/50) | 0.50 |
| Random | 36 (13/36) | 13 (6/46) | 18 (9/50) | 0.03 |
| Fibrosis | ||||
| Upper lobe | 100 (36/36) | 96 (44/46) | 62 (31/50) | <0.001 |
| Peripheral | 78 (28/36) | 100 (46/46) | 92 (46/50) | 0.002 |
| Basal | 39 (14/36)a | 76 (35/46) | 84 (42/50) | <0.001 |
| Basal predominance of honeycombing | 11 (4/36) | 52 (24/46)a | 4 (2/50) | <0.001 |
| Relative sparing of bases | 39 (14/36)a | 11 (5/46) | 6 (3/50) | <0.001 |
| Air trapping | 75 (18/24) | 35 (7/20) | 10 (2/20) | <0.003 |
Used with permission from Silva CI et al. Radiology. 2008;246:288-297.
