The number of topics arranged in descending determined in each study using latent Dirichlet allocation as a type of unsupervised learning approach
| Author | Data source | No. of topics |
| Kowalksi | NHS choices | 60 |
| Ranard et al56 | Yelp | 50 |
| Bahja et al26 | NHS choices | 30 |
| Doing-Harris et al24 | Press Ganey | 30 |
| Hao et al51 | Haodf | 10 |
| James et al53 | RateMDs | 6 |