Table 5. Clinical and laboratory characteristics according to the SpO2 decline induced by the 6-minute walking test.
| Decline<3%(n = 21) | Decline≥3% (n = 17) | P value | |
| Medical history | |||
| Age (yrs) | 10.5 (5.7–17.0) | 11.5 (6.2–15.6) | 0.32 |
| Male gender | 3 (14.3%) | 10 (58.8%) | 0.004 |
| BMI (Kg/m2) | 16.1 (13.3–24.0) | 16.9 (14.0–21.4) | 0.62 |
| Enlarged tonsils | 8 (40%) | 7 (43.8%) | 0.82 |
| N of VOC in the past year | 0 (0–7) | 0 (0–6) | 0.22 |
| Hydroxycarbamide treatment | 6 (28.6%) | 3 (17.6%) | 0.48 |
| Past history of at least one ACS episode | 8 (38.1%) | 7 (41.2%) | 0.85 |
| Abnormal lung function test | 6 (28.6%) | 8 (47.1%) | 0.24 |
| SpO2 values | |||
| Daytime SpO2 | 98 (89–100) | 96 (92–100) | 0.44 |
| Lowest nocturnal SpO2 | 95.5 (87.5–99.5) | 92.0 (87.8–96) | 0.051 |
| % sleep time with SpO2<90% | 0.3 (0–90.6) | 9 (0.1–68.2) | 0.048 |
| Laboratory tests | |||
| Hemoglobin (g/dL) | 8.2 (6.6–10.2) | 7.5 (5.2–10.6) | 0.08 |
| Leukocytes (Giga/L) | 10.7 (5.7–16.0) | 11.4 (7.7–21.5) | 0.92 |
| Reticulocyte count (Giga/L) | 232 (43–443) | 239 (104–357) | 0.90 |
| Lactate dehydrogenase (IU/L) | 1130 (618–1731) | 1467 (849–1893) | 0.17 |
| Total bilirubin (µmol/L) | 47 (13–130) | 39 (13–161) | 0.55 |
| Aspartate aminotransferase (IU/L) | 56 (35–132) | 66 (39–93) | 0.06 |
| Fetal hemoglobin (%) | 10.1 (2.6–28) | 7.1 (3.9–20.2) | 0.46 |
| Creatinine (µmol/L) | 37 (20–53) | 35 (22–57) | 0.20 |
| 6 MWT distance (% predicted distance) | 92 (46–120) | 86 (73–102) | 0.71 |
BMI, body mass index; VOC, vasoocclusive crisis; ACS, acute chest syndrome; 6 MWT, 6-minute walking test.