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Vitamin A

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Vitamin A * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Xerophthalmia Classification XN X1A X1B ... – PowerPoint PPT presentation

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Title: Vitamin A


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Vitamin A
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Xerophthalmia Vernacular Terms
Matang Manok Mata Ajam Khwak
Moan Gred Gradei Mager Aagh
Korapothu
Chicken Eyes Chicken Eyes Dusk Blindness Scaly
as Fish Fish Scales Scaly
Tagalog Indonesian Khmer Thai
Bengali Singhalese
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Impact of VADD on Public Health
  • 250 million preschool-age children have
    subclinical vitamin A deficient
  • 7.2 million pregnant women
  • 3 million have clinical xerophthalmia
  • 300, 000 are blind from xerophthalmia

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Impact of Vitamin A Intervention on Child Survival
Improvement of vitamin A status in young child
populations leads to a reduction in all-cause
mortality rates of about 23. United Nations,
1993
Improved vitamin A nutriture would be expected
to prevent approximately 1.3-2.5 million deaths
annually among children aged under 5
years. Bulletin of WHO, 1992 BUT Mechanisms
involved are poorly understood
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Functions
  • Vision (night, day, colour)
  • Epithelial cell integrity against infections
  • Immune response
  • Haemopoiesis
  • Skeletal growth
  • Fertility (male and female)
  • Embryogenesis

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Tests of Vitamin A Status
Subclinical
  • Relative dose-response test
  • Serum retinol
  • Retinal rod function
  • Conjunctival impression





    cytology (CIC)

Decreased Status
Clinical
  • Night blindness
  • Conjunctival and corneal eye signs

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Factors that may Affect Plasma Vitamin A or
Retinol Levels
  • Liver disease deacreases plasma retinal levels,
    probably as a result of a combination of
    decreased synthesis and secretion of RBP.
  • Stress decreases plasma retinol levels.
  • Protein-energy malnutrition decreases RBP
    production because of a limited supply of protein
    substrate. Consequently hepatic release of
    vitamin A is impaired resulting in decreased
    serum retinol levels.
  • Zinc deficiency decreases plasma retinol levels
    via its role in the synthesis of RBP.

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  • Infections and parasitic infections lower plasma
    retinol levels.
  • Cystic fibrosis is associated with a defect in
    the transport of vitamin A from the hepatic
    stores to the periphery resulting in decreased
    levels of circulating retinol and RBP.
  • Low fat diets impair absorption of vitamin A,
    lowering plasma retinol concentrations.
  • Estrogens, either endogenous or those used in
    contraceptive agents, increase plasma retinol and
    RBP apparently as a result of incresed
    mobilization of Vitamin A from the liver.
  • Age, sex and race influence serum retinol
    levels, as indicated by the NHANES II survey
    results.

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For the test, a baseline blood sample is taken
immediately before the administration of a small
oral dose (450µg) of vitamin A (as retinyl
acetate or retinol palmitate) followed by a
second blood sample, five hours later. The RDR
() is calculated as
Plasma retinol at 5 hr Plasma retinol at 0hr
X 100
RDR()
Plasma retinol at 5 hr
Vitamin-A-replete subjects have RDR values
ranging from 0 to 14. Relative dose response
values greater than 14 to 20 are indicative of
marginal vitamin A status in humans, the cutoff
value depending on the coefficient of variation
for the analytical method used to measure serum
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Percentage of Children with Positive RDR Test
Classified by Serum Retinol Levels
Serum Retinol (µg/dL)

Number Tested
lt20
100
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21 - 29
86
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30 - 40
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19
gt40
3
39
91
Total tested
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Treatment Schedule (orally)
Immediately on diagnosis
50, 000 IU
lt6 months
100, 000 IU
6 months-12 months
200, 000 IU
gt 12 months
Next day
Same age-specific dose
At least two weeks later
Same age-specific dose
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Xerophthalmia Classification
XN
Night Blindness
X1A
Conjunctival Xerosis
X1B
Bitots Spot with Conjunctival Xerosis
X2
Corneal Xerosis
X3A
Corneal Xerosis with ulceration
X3B
Keratomalcia
XF
Xerophthalmic Fundus
XS
Corneal scars from Xerophthalmia
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WHO criteria of a public health problem of
xerophthalmia
  • Night Blindness

(XN)
In gt 1
  • Bitots spot

(X1B)
In gt 0.5
  • Corneal Xerosis/Ulceration/Keratomalacia

In gt0.01
(X2, X3A, X3B)
  • Corneal scar

(XS)
In gt 0.05
  • Plasma retinol of lt0.35µmol/l (10 µg/dl)

In gt 5
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Percent with Serum Vitamin A
n
lt10 µg/dL
10-19 µg/dL
gt20 µg/dL
252
8
37
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Normal Children
Children with night-blindness or Bitots spots
325
30
15
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Children with corneal xerophthalmia
75
98
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1
Serum vitamin A levels in a sample of Indonesian
children with and without ocular lesions.
Conversion factor SI units(µmol/L) x 0.035
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