DETERMINING STATUS

There are several ways of determining vitamin A status:

1. Clinical symptoms

• Xerophthalmia can be observed by conjunctival impression cyotology
  (a technique to study various dry eye states
  without the need of biopsy from the conjunctiva )
• Dark adaptation/night blindness

2. Dietary reports

3. Biochemical analysis

• Liver stores
• Plasma retinol
• Plasma RBP
• Relative dose response (RDR)

RDR measures the difference in plasma retinol from a fasting blood sample (i.e. time = 0) and 5 hours after a 450 mg retinol dose (in oil solution) is given per os.

RDR is expressed as %: [k5t –k0t] X 100 / k5t

The presence of xerophthalmia and/or the concentrations of retinol in plasma are most often used.

Deficiency related to clinical symptoms