Novel Spectrophotometric Method for the Quantitation of Urinary Xanthurenic Acid and Its Application in Identifying Individuals with Hyperhomocysteinemia Associated with Vitamin B₆ Deficiency

Table 2

A single blind study for 20 hyperhomocysteinemic urine specimens obtained through a small-scale screening of the elderly (𝑛=80) for assaying XA by our proposed method and their parallel comparison of assessing B₆ status by indirect activation coefficient test for RBC/AST.

Specimen code no.	XA determined* by the proposed method (mg/L)	Indirect activation coefficient (AC) test for RBC/AST**
1	ND	Normal
2	ND	Normal
3	ND	Normal
4	13.5	Abnormal (AC = 1.51)
5	ND	Normal
6	ND	Normal
7	14.2	Abnormal (AC = 1.43)
8	ND	Normal
9	ND	Normal
10	ND	Normal
11	ND	Normal
12	ND	Normal
13	25.3	Abnormal (AC = 1.80)
14	ND	Normal
15	ND	Normal
16	ND	Normal
17	ND	Normal
18	ND	Normal
19	ND	Normal
20	ND	Normal

∗ND: nondetectable (<LOD).
**AC < 1.30 is designated as normal.