Frequency of clinical variables in paediatrics patients (aged 6–18 years) with sickle cell anaemia (SCA) from the UK (n=101) and Nigeria (NIG) (n=154)
| Variable | SCA UK (%) | SCA NIG (%) | P value |
| Current hydroxyurea treatment | 47.5 | 0.6 | <0.001 |
| Asthma* | 21.7 | 6.7 | <0.001 |
| At least three pain crises in the last year† | 24.7 | 49.3 | <0.001 |
| Previous acute chest syndrome‡ | 34.5 | 21.4 | 0.02 |
*Parent report or medical record evidence of physician-diagnosed asthma.
†Pain crises requiring analgesic therapy for at least 24 hours.
‡Fever and/or respiratory symptoms, accompanied by a new pulmonary infiltrate on a chest X-ray.22