Table 5.

Studies that assessed 25(OH)D levels in patients diagnosed with NF1.

Author	Country	Method for dosing 25(OH)D levels∗	Study design	Mean age, years (cases: controls)	Number (female/male rate)	25(OH)D levels	Results (p value)
Lammert et al., 2006 [14]	Germany	CLBPA: autumn or winter	Case-control	40.3 : 36	55 cases (33 : 22), 58 controls (38 : 20)	Mean: 15.7 ng/mL (cases): 35.5 ng/mL (controls)	Lower 25(OH)D levels in NF1 patients (p < 0.0001) and inverse correlation with the number of neurofibromas (p < 0.0003)
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 (cases)	72 cases (43 : 29)	<20 ng/mL in 56% (cases)	Lower 25(OH)D levels in NF1 patients (p < 0.001)
Seitz et al., 2010 [11]	Germany	RIA: autumn, winter, and spring	Case-control	44.36 : 46.97	14 cases (9 : 5), 42 controls (27 : 15)	Range: 5–23 ng/mL (cases): 13–46 ng/mL (controls)	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), 218 controls	Mean: 31.76 ng/mL (cases): 33.79 ng/mL (controls)	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, 60 controls	Mean: 21.8 ng/mL (cases): 32.9 ng/mL (controls)	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), 15 controls (8 : 7)	Mean: 15.6 (cases) 16.6 (controls)	25(OH)D levels were not significantly different between groups; overall mean in total population was within deficient range

NF: neurofibromas; 25(OH)D: 25-hydroxy-vitamin D; CLBPA: chemiluminescence binding protein assay; RIA: radioimmunoassay; CLIA: chemiluminescence intra-assay.

^∗Levels and cutoff values may vary according to the method used in the dosage.