A 56-year-old man with a history of intravenous drug use and multiple infectious complications developed candida fungemia, which was initially treated with fluconazole and then liposomal amphotericin. At admission, he had normal calcium, phosphate, and magnesium but developed persistent hyperphosphatemia (phosphotungstate on Beckman DCxI) with values of 5 to 6.5 mg/dL (reference interval 2.5–4.5 mg/dl) despite only mild, stable renal dysfunction [normal blood urea nitrogen, creatinine 1.5–1.9 mg/dL (reference interval 0.8–1.5 mg/dL)] and continued normal calcium. He also had normal globulins. 

Questions

  1. What are common causes of high phosphate?
  2. What artifacts cause increased phosphate?
  3. What is the likely cause of increased phosphate in this patient?

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