Patient demographics and clinical characteristics
| Clinical variables . | Total n = 471 (%) . | Alloimmunized, n = 55 (%)∗ . | Nonalloimmunized, n = 416 (%) . |
|---|---|---|---|
| Sex | |||
| Female | 229 (48.6%) | 28 (50.9%) | 201 (48.3%) |
| Male | 242 (51.4%) | 27 (49.1%) | 215 (51.7%) |
| Race | |||
| Black | 467 (99.2%) | 55 (100.0%) | 412 (99.0%) |
| Black and White | 1 (0.2%) | — | 1 (0.2%) |
| White | 2 (0.4%) | — | 2 (0.5%) |
| Others | 1 (0.2%) | — | 1 (0.2%) |
| Hb genotypes | |||
| SS/Sβ0 thalassemia | 384 (81.5%) | 50 (90.9%) | 334 (80.3%) |
| SC | 65 (13.8%) | 3 (5.5%) | 62 (14.9%) |
| Sβ+ thalassemia | 20 (4.2%) | 2 (3.6%) | 18 (4.3%) |
| Others | 2 (0.4%) | — | 2 (0.5%) |
| Blood transfusion | |||
| Age at first transfusion (y) | 4.6 (∼1.9-8.1) | 4.9 (∼2.7-6.8) | 4.5 (1.7-∼8.3) |
| Transfusion period (y) | |||
| Total | 6.4 (∼3.5-10.3) | 6.9 (∼4.011.9) | 6.3 (∼3.3-10.2) |
| Before alloimmunization | — | 4.1 (∼0.9-7.8) | — |
| Transfusion load (units) | |||
| Total | 3 (∼2-9) | 16 (∼3-168) | 3 (∼1-7) |
| Before alloimmunization | — | 17 (∼3-61) | — |
| Transfusion frequency | |||
| Chronic transfusion | |||
| No. of patients | 69 (15.0%) | 25 (56.8%) | 44 (10.6%) |
| Transfusion load (units) | |||
| Total | 143 (∼70-312) | 168 (∼84-293) | 138 (∼62-315) |
| Before alloimmunization | — | 55 (∼31-90) | — |
| Episodic transfusion | |||
| No. of patients | 391 (85.0%) | 19 (43.2%) | 372 (89.4%) |
| Transfusion load (units) | |||
| Total | 3 (∼1-5) | 5 (∼2-9) | 3 (∼1-5) |
| Before alloimmunization | — | 2 (∼2-5) | — |
| HU treatment | |||
| Yes | 298 (76.2%) | 18 (94.7%) | 280 (75.3%) |
| No | 93 (23.8%) | 1 (5.3%) | 92 (24.7%) |
| Age starting HU (y) | 5.7 (∼2.9-9.4) | 3.5 (∼2.1-7.2) | 5.8 (∼2.9-9.4) |
| HU therapy duration (y)† | |||
| Total | 4.37 (∼2.49-8.31) | 7.73 (∼4.84-9.56) | 4.20 (∼2.40-8.26) |
| Before alloimmunization | — | 4.50 (∼0.67-6.79) | — |
| HU MTD (mg/kg per d) | |||
| Total | 29.2 (∼23.6-30.8) | 30.0 (∼28.3-30.1) | 29.0 (∼23.0-31.0) |
| Before alloimmunization | — | 30.0 (∼28.3-30.1) | — |
| Clinical variables . | Total n = 471 (%) . | Alloimmunized, n = 55 (%)∗ . | Nonalloimmunized, n = 416 (%) . |
|---|---|---|---|
| Sex | |||
| Female | 229 (48.6%) | 28 (50.9%) | 201 (48.3%) |
| Male | 242 (51.4%) | 27 (49.1%) | 215 (51.7%) |
| Race | |||
| Black | 467 (99.2%) | 55 (100.0%) | 412 (99.0%) |
| Black and White | 1 (0.2%) | — | 1 (0.2%) |
| White | 2 (0.4%) | — | 2 (0.5%) |
| Others | 1 (0.2%) | — | 1 (0.2%) |
| Hb genotypes | |||
| SS/Sβ0 thalassemia | 384 (81.5%) | 50 (90.9%) | 334 (80.3%) |
| SC | 65 (13.8%) | 3 (5.5%) | 62 (14.9%) |
| Sβ+ thalassemia | 20 (4.2%) | 2 (3.6%) | 18 (4.3%) |
| Others | 2 (0.4%) | — | 2 (0.5%) |
| Blood transfusion | |||
| Age at first transfusion (y) | 4.6 (∼1.9-8.1) | 4.9 (∼2.7-6.8) | 4.5 (1.7-∼8.3) |
| Transfusion period (y) | |||
| Total | 6.4 (∼3.5-10.3) | 6.9 (∼4.011.9) | 6.3 (∼3.3-10.2) |
| Before alloimmunization | — | 4.1 (∼0.9-7.8) | — |
| Transfusion load (units) | |||
| Total | 3 (∼2-9) | 16 (∼3-168) | 3 (∼1-7) |
| Before alloimmunization | — | 17 (∼3-61) | — |
| Transfusion frequency | |||
| Chronic transfusion | |||
| No. of patients | 69 (15.0%) | 25 (56.8%) | 44 (10.6%) |
| Transfusion load (units) | |||
| Total | 143 (∼70-312) | 168 (∼84-293) | 138 (∼62-315) |
| Before alloimmunization | — | 55 (∼31-90) | — |
| Episodic transfusion | |||
| No. of patients | 391 (85.0%) | 19 (43.2%) | 372 (89.4%) |
| Transfusion load (units) | |||
| Total | 3 (∼1-5) | 5 (∼2-9) | 3 (∼1-5) |
| Before alloimmunization | — | 2 (∼2-5) | — |
| HU treatment | |||
| Yes | 298 (76.2%) | 18 (94.7%) | 280 (75.3%) |
| No | 93 (23.8%) | 1 (5.3%) | 92 (24.7%) |
| Age starting HU (y) | 5.7 (∼2.9-9.4) | 3.5 (∼2.1-7.2) | 5.8 (∼2.9-9.4) |
| HU therapy duration (y)† | |||
| Total | 4.37 (∼2.49-8.31) | 7.73 (∼4.84-9.56) | 4.20 (∼2.40-8.26) |
| Before alloimmunization | — | 4.50 (∼0.67-6.79) | — |
| HU MTD (mg/kg per d) | |||
| Total | 29.2 (∼23.6-30.8) | 30.0 (∼28.3-30.1) | 29.0 (∼23.0-31.0) |
| Before alloimmunization | — | 30.0 (∼28.3-30.1) | — |
Categorical variables summarized as n (%), and continuous variables summarized as median (IQR, Quartile 1 to Quartile 3).
Among 55 patients who were alloimmunized, 11 were alloimmunized before transfusion at our center. Their data about sex, race, and Hb genotypes were included for alloimmunization association analysis. Their histories of blood transfusion and HU therapy before alloimmunization were unknown so were not included in the analysis.
Included episodically transfused patients who received HU therapy only.