Author Country Method for dosing 25(OH)D levels Study design Mean age, years Number (female/male rate) 25(OH)D levels Results ( Lammert et al., 2006 [14 ] Germany CLBPA: autumn or winter Case-control 40.3 : 36 55 cases (33 : 22), Mean: 15.7 ng/mL (cases): Lower 25(OH)D levels in NF1 patients ( Brunetti-Pierri et al., 2008 [9 ] USA Chromatography Descriptive 13.5 (cases) 16 cases with osteoporosis or osteopenia Mean: 20.6 ng/mL (cases) — Tucker et al., 2009 [10 ] Germany Technical unreported: winter and summer Case-control Men 43.4 and women 42.1 72 cases (43 : 29) <20 ng/mL in 56% (cases) Lower 25(OH)D levels in NF1 patients ( Seitz et al., 2010 [11 ] Germany RIA: autumn, winter, and spring Case-control 44.36 : 46.97 14 cases (9 : 5), Range: 5–23 ng/mL (cases): Lower 25(OH)D levels in NF1 patients (<0.05) Stevenson et al., 2011 [15 ] USA CLIA Case-control 9.3 (controls) 109 cases (50 : 59), Mean: 31.76 ng/mL (cases): Lower 25(OH)D levels in NF1 patients (0.0129) Petramala et al., 2012 [12 ] Italy RIA: autumn and winter Case-control 41.1 : 44.3 70 cases, Mean: 21.8 ng/mL (cases): Lower 25(OH)D levels in NF1 patients (<0.01) Hockett et al., 2013 [16 ] United Kingdom Chromatography Case-control 11.8 : 11.5 15 cases (10 : 5), Mean: 15.6 (cases) 25(OH)D levels were not significantly different between groups; overall mean in total population was within deficient range
