Table 1.
Comparisons of sample characteristics (mean ± SD, or median with range, or frequency) between the analysis data and the entire cohort with no statistically significant demographic or clinical differences
| Variables | Analysis data (n=521) | Entire cohort (n=1016) | P-value |
|---|---|---|---|
| Age (years) | 9.1 ± 2.1 | 9.1 ± 2.4 | 0.95 |
| Sex: | |||
| Male | 271 | 521 | 1.00 |
| Female | 250 | 480 | |
| Hemoglobin type: | |||
| SS | 470 | 883 | 0.74 |
| SB zero | 31 | 64 | |
| White blood count (/mm3) | 12000 (1080–147000) | 12000 (1055–151000) | 0.76 |
| Hemoglobin (g/dL) | 8.0 ± 1.0 | 8.1 ± 1.0 | 0.21 |
| Fetal hemoglobin (%) | 11 (1–98) | 11 (0–98) | 0.98 |
| Household smoking: | |||
| Yes | 121 | 252 | 0.45 |
| No | 381 | 716 | |
| Patient asthma: | |||
| Yes | 140 | 245 | 0.32 |
| No | 381 | 756 | |
| Clinical site: | |||
| North America | 460 | 877 | 0.34 |
| Europe | 61 | 138 | |
| Parental asthma: | |||
| Yes | 112 | 190 | 0.22 |
| No | 397 | 794 | |
| ACS rate (/100 patient-years) | |||
| Asthma | 19 (14–25); p=0.02* | 22 (18–27); p<0.0001# | 0.68 |
| No-asthma | 12 (10–15) | 12 (10–14) | |
| Pain rate (/100 patient-years) | |||
| Asthma: | 67 (54–83); p=0.046* | 73 (61–87); p<0.0176# | 0.14 |
| No-asthma: | 51 (45–59) | 57 (52–63) | |
In the first 521 participants, a doctor diagnosis of asthma was associated with increased incidence rates of ACS and pain episodes. After final adjustment for age, hemoglobin F and baseline hemoglobin levels, ACS incidence rates were 19 (95% CI 14 – 25) and 12 (95% CI 10 – 15) episodes per 100 patient-years among children with and without an asthma diagnosis, respectively (p = 0.02); pain rates were 67 (95% CI 54 – 83) and 51 (95% CI 45 – 59) episodes per 100 patient-years among children with and without an asthma diagnosis, respectively (p = 0.046).
In the entire cohort, a doctor diagnosis of asthma was associated with increased incidence rates of ACS and pain episodes. After final adjustment for age, hemoglobin F and baseline hemoglobin levels, ACS incidence rates were 22 (95% CI 18 – 27) and 12 (95% CI 10 – 14) episodes per 100 patient-years among children with and without an asthma diagnosis, respectively (p < 0.0001); pain rates were 73 (95% CI 61 – 87) and 57 (95% CI 52 – 63) episodes per 100 patient-years among children with and without an asthma diagnosis, respectively (p = 0.0176).