Table 2.

Clinical correlates of low BMD in the SCCRIP BMD cohort

VariableAll (N = 306)Female (n = 153)Male (n = 153)
Normal BMD (n = 250 [81.7%])Low BMD (n = 56 [18.3%])Normal BMD (n = 128 [83.7%])Low BMD (n = 25 [16.3%])Normal BMD (n = 122 [79.7%])Low BMD (n = 31 [20.3%])
SCD genotype
 HbSS/Sβ0-thalassemia152 (60.8)*45 (80.4)*75 (58.6)*19 (76.0)*77 (63.1)*26 (83.9)*
 HbSC76 (30.4)*4 (7.1)*44 (34.4)*2 (8.0)*32 (26.3)*2(6.4)*
 HbSβ+-thalassemia22 (8.8)*7 (12.5)*9 (7.1)*4 (16.0)*13 (10.7)*3 (9.7)*
Age at DXA, y11.9 ± 4.09*14.5 ± 2.75*12.2 ± 4.1814.2 ± 2.7711.7 ± 3.98*14.7 ± 2.77*
Age category
 School-age92 (36.8)*4 (7.1)*44 (33.9)*2 (8.0)*48 (39.3)*2 (6.5)*
 Adolescent158 (63.2)*52 (92.9)*84 (65.6)*23 (92.0)*74 (60.7)*29 (93.6)*
VOEs per year (total)0.25 ± 0.440.22 ± 0.480.21 ± 0.370.27 ± 0.590.29 ± 0.500.19 ± 0.39
VOEs per year (2 y to DXA)0.58 ± 2.120.71 ± 1.700.47 ± 1.480.56 ± 1.230.69 ± 2.540.84 ± 2.57
VOEs total (categorical)
 <5 times141 (56.4)35 (62.567 (52.3)17 (68.0)74 (60.7)18 (58.1)
 5-10 times63 (25.2)11 (19.6)43 (33.6)3 (12.0)20 (16.4)8 (25.8)
 >10 times46 (18.4)10 (17.9)18 (14.1)5 (20.0)28 (22.9)5 (16.1)
Hydroxyurea use
 No109 (43.6)16 (28.6)57 (44.5)8 (32.0)52 (42.6)8 (25.8)
 Yes141 (56.4)40 (71.4)71 (55.5)17 (68.0)70 (57.4)23 (74.2)
Hydroxyurea duration
 <5 y187 (74.8)34 (60.7)97 (75.8)16 (64.0)90 (73.6)18 (58.1)
 5-10 y41 (16.4)15 (27.8)22 (17.2)7 (28.0)19 (15.6)8 (25.8)
 >10 y22 (8.8)7 (12.5)9 (7.0)2 (8.0)13 (10.7)5 (16.1)
Hydroxyurea duration, y2.9 ± 3.95*4.1 ± 4.31*2.8 ± 3.883.6 ± 3.883.1 ± 4.034.4 ± 4.66
Chronic RBC transfusions
 No245 (98.0)52 (92.9)125 (97.7)22 (88.0)120 (98.4)30 (96.8)
 Yes5 (2.0)4 (7.1)3 (2.3)3 (12.0)2 (1.6)1 (3.2)
Chronic pain
 No244 (97.6)51 (91.1)125 (97.7)24 (96.0)119 (97.5)27 (87.1)
 Yes6 (2.4)*5 (8.9)*3 (2.3)1 (4.0)3 (2.5)*4 (12.9)*
Hip osteonecrosis
 No242 (96.8)49 (87.5)126 (98.4)24 (96.0)116 (95.1)25 (80.7)
 Yes8 (3.2)*7 (12.5)*2 (1.6)1 (4.0)6 (4.9)*6 (19.3)*
Hip osteonecrosis grade
 Less severe3 (1.2)*2 (3.6)*1 (0.8)0 (0)2 (1.6)*2 (6.5)*
 Severe5 (2.0)*5 (8.9)*1 (0.8)1 (4.0)4 (3.3)*4 (12.9)*
 None242 (96.8)49 (87.5)126 (98.4)24 (96.0)116 (95.1)25 (80.6)
Vitamin D status§
 Normal68 (28.8)9 (17.7)31 (25.4)2 (8.0)37 (32.5)7 (26.9)
 Insufficient91 (38.6)23 (45.1)54 (44.3)10 (40.0)37 (32.5)13 (50.0)
 Deficient77 (32.6)19 (37.3)37 (30.3)13 (52.0)40 (35.1)6 (23.1)
  • Data are presented as n (%) or mean ± standard deviation.

  • * P < .05 between low vs normal BMD per variable.

  • Defined as RBC transfusions ≥4 times/year.

  • Less severe, necrotic lesion ≤30% femoral head volume; severe, necrotic lesion >30% femoral head volume.

  • § Normal, 25(OH)D, >30 ng/mL; insufficient, 25(OH)D 20 to 30 ng/mL; and deficient, 25(OH)D <20 ng/mL.