A urine sample submitted for a urinary calcium-to-creatinine ratio was visually clear but deep orange in color (Fig. 1, left). Acidification of the sample to pH <2.0 with HCl prior to analysis produced a color change in the sample from orange to deep red (Fig. 1, right). The 16-year-old female patient had a history of polycystic ovarian syndrome, oligomenorrhea, and vitamin D deficiency and a suspected urinary tract infection.

  1. What could have contributed to the peculiar color change phenomenon of this patient's urine sample?
  2. What phenomenon in this urine sample differentiates it from the other causes of similarly colored urine?
  3. Is this sample suitable for calcium (o-cresolphthalein) and creatinine (Jaffe) analysis?

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