| First author [ref.] | Main conclusion | SIGN grade | Study type | Exposure/ occupation | Subjects n |
| Merget [10] | No relationship | 2- | Cohort study | Platinium salts | 275 |
| Descatha [28] | No relationship | 2+ | Case series | Various HMW and LMW agents | 227 |
| Cote [12] | No relationship | 2+ | Longitudinal | Plicatic acid (Western red cedar) | 48 |
| Valentino [29] | No relationship | 2+ | Longitudinal | TDI | 50 |
| Park [16] | No relationship | 2- | Longitudinal | TDI | 35 |
| Lozewicz [18] | No relationship | 2+ | Longitudinal | Isocyanates (TDI, MDI) | 56 |
| Anees [31] | No relationship | 2+ | Longitudinal | Various HMW and LMW agents | 156 |
| Park [21] | No relationship | 2- | Longitudinal | TDI | 41 |
| Mapp [22] | No relationship | 2- | Longitudinal | TDI | 35 |
| Merget [38] | No relationship | 2- | Longitudinal | Platinium salts | 24 |
SIGN: Scottish Intercollegiate Guidelines Network; HMW: high molecular weight; LMW: low molecular weight; TDI: toluene diisocyanate; MDI: methylene diphenyl diisocyanate.