Severe subacute combined degeneration of the spinal cord resulting from nitrous oxide (N2O) abuse: a case series

Table 2 Laboratory findings of seven patients of N2O-induced SACD

Patient	Cobalamin (Vitamin B12) [191–663 ng/l]	Folic Acid [4.6–18.7 µg/l]	Holotranscobalamin [37.5–188 pmol/l]	Methylmalonic acid [< 32 µg/l]	Homocysteine [< 15 µmol/l]	Hemoglobin [13.5–17/12-15.6\|	MCV [80–99 fl]	MCH [27–33.5 pg]	Anti-T.pallidum³	Anti-HIV 1/2⁴
Patient #1	< 100*	12.4	> 300*	368.5*	7.1²	11.9*	102.3*	34.4*	Neg	Neg
Patient #2	173*	9.5	47.1	713*	n/a	13.6	98.3	32.5	Neg	Neg
Patient #3	341	15.9	n/a	119.0*	21.2*	14.6	95.2	33.6*	Neg	Neg
Patient #4	332	n/a	58.9	78.0*	20.7*	13.4	94.9	33.8*	n/a	n/a
Patient #5	74*	8.8	n/a	15.9 *¹	21.4*	12.6*	97.0	32.1	Neg	Neg
Patient #6	131*	3.5*	63.9	153.5*	49.1*	12.9*	97.0	31.9	Neg	Neg
Patient #7	380	10.7	> 300*	205.8*	97.8*	12.8*	90.6	32.3	n/a	n/a

*, abnormal values, n/a: data not available, 1: In patient #5, methylmalonic acid was measured in urine. Reference value for methylmalonic acid in urine is < 5.0 mmol/mol creatinine, 2: collected with a delay of 11 days after vitamin b12 substitution, 3: western immunoblot assay, 4: Electrochemiluminescence (ECL)

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