The control of vitamin A deficiency in many areas of the world
will lead to substantial and lasting improvement in childhood survival as well as
preventing the scandal of irreversible blindness due to malnutrition. (ACC/ SCN
Consultative Group)
Sub-clinical vitamin A deficiency increases risks of ill-health and
death in at least a quarter of the children in developing countries (140 million)
Causes
General-
- Inadequate intake of carotene or performed vitamin A (in foods such as
liver, egg yolks, dairy products, dark green leafy vegetables, yellow and orange fruits
and vegetables)
- Poor absorption of vitamin A from foods due to intestinal parasitic
infections, gastro-enterititis, or malabsorption
- Increased (and unmet) metabolic demand for vitamin A, usually in periods
of rapid growth as seen in infants, children, and pregnant women
Manifestations
(especially in pre-school age children, adolescents, and pregnant women)
Eye signs- a series of
degradations in the integrity of the eye occur as the level of vitamin A stores are
depleted from the body. First, the eye will no longer produce rhodopsin, a substance
that allows for vision in dim light-- resulting in nightblindness. Then, the eye may
become dry and spots might occur on the white's of the eye (bitot's spots) and corneal
disruptions may begin to form-- different forms of xeropthalmia (conjunctival xerosis,
Bitot’s spots, corneal xerosis, corneal ulceration, keratomalacia, corneal scars,
xeropthalmia fundus). Then openings in the cornea might result, ulceration and next
the tissue will begin to keratinize.
Blindness-a final result of
long periods of vitamin A deficiency, which can be followed by death if supplementation is
not given.
Morbidity and Mortality-
Vitamin A plays an important role in the integrity of tissues in the body and therefore to
the risk of infection. It has been found in repeated studies (both animal and human
models) that the risk of infection when the body lacks sufficient vitamin A is drastically
increased. A publication by Scrimshaw et. al. in the 1960s concluded that VAD showed
synergism with almost every known infectious disease. It has been speculated that up
to 3 million children's lives might be saved annually by improving global vitamin A status
(Gillespie and Mason, 1994).
Indicators
Process and Outcome Indicators of Vitamin A Deficiency
| Indicator type |
Indicator |
| Process and Other Non-Outcome
Indicators |
- Dietary intake - especially
for children 6- 71 months, pregnant women, and lactating women including food frequency
questionnaires (FFQ) and dietary recall surveys to assess intake of Vitamin A foods
- Disease prevalence -
diarrhea, fever, measles, helminth infections (esp. ascaris)
- Vitamin A Supplementation
- Food Availability in the market or Household (seasonality
of Vit A foods)
- Duration of breastfeeding or non-exclusive in first 6
months (continuation with complelmentary feeding to 18 months)
- Birth weight - children
born <2500 grams are at risk
- General nutrition status -
stunting and wasting
- Immunization coverage -
especially measles
- Maternal education and literacy
- Family income level
- Water supply and sanitation
- Access to health care
- Access to land
- Caring capacity for the child
|
| Outcome |
Clinical |
Eye signs-
- Nightblindness (XN) - cannot see
properly in dim light
- Bitot’s spots (X1B) - foamy
whitish patches on the whites of the eyes
- Conjunctival xerosis (X1B) - drying
of the white of the eye
- Active corneal lesions - the
clear part of the eye is damaged
- Corneal xerosis (X2) - drying of
the cornea, scaly appearance
- Corneal ulcers (X3A) - formation
of holes on the cornea
- Keratomalacia (X3B) - cornea
becomes cloudy and soft
- Corneal scars (XS) - scar on the
cornea
|
| Sub-clinical |
Blood- Serum retinol level <0.35µmol/l
in >5% of the population constitues a public health
problem Other-
- Breast milk retinol
- Relative dose response test (RDR)
- Modified relative dose response test (MRDR)
- Conjunctival impression cytology (CIC)
|
Sources:Process indicators are summarized from John’s notes
P3A 21 Causes of VAD (Table 2 Causes of Vitamin Adeficiency among young children) and
Prevention of Micronutrient Deficiencies Ch 4 Tables 4-3A thru 4-3C by Barbara Underwood,
National Academy Press, Washington DC 1998. Outcome indicators summarized from Present
Knowledge in Nutrition Ch 19 Vitamin A and other vitamin deficiencies, 1997 and Prevention
of Micronutrient Deficiencies Ch 4 Tables 4-1 by Barbara Underwood, National Academy
Press, Washington DC 1998.
****
Most sensitive group used for detection of VAD: Preschool children
(6-71 months)
****
Outcome Indicators for Vitamin A Deficiency
Cut-offs at the individual and population level
| Indicator |
Individual
Level |
Population
Level (%)
(to be defined as a public health problem) |
Moderate |
Severe |
Mild |
Moderate |
Severe |
eye signs:
Nightblindness (XN)
(children 24-71 months) |
(present- y/n)
|
(present- y/n)
|
>0 to <1
|
³ 1 to <5
|
³ 5
|
Conjunctival xerosis (x1A)
(children 6-71 months) |
(present- y/n)
|
(present- y/n)
|
--
|
-- |
--
|
Bitot’s Spots (x1B)
(children 6-71 months) |
(present- y/n)
|
(present- y/n)
|
--
|
0.5%
(n³ 3058) |
--
|
X2, X3A, X3b
(children 6-71 months) |
(present- y/n)
|
(present- y/n)
|
--
|
0.01%
(n³ 153,650) |
--
|
Corneal Scars (XS)
(children 6-71 months) |
(present- y/n)
|
(present- y/n)
|
--
|
0.05%
(n³ 30,718) |
-- |
Blood signs:
Serum Retinol
(children 6-71 months) |
<0.7 umol/l
|
<0.35 umol/l
|
>0 to <10
(<0.7 umol/l) |
³
10 to <20 (<0.7 umol/l) |
³
20
(<0.7 umol/l) |
Other signs:
Breast milk retinol
(children 6-71 months) |
£
1.05umol/l
(£ 8ug/g milk fat) |
--
|
<10
|
³ 10 to <25
|
³ 25
|
RDR
(children 6-71 months) |
³ 20%
|
--
|
<20
|
³ 20 to <30
|
³ 30
|
MRDR
(children 6-71 months) |
Ratio ³ 0.06
|
--
|
<20
|
³ 20 to <30
|
³ 30
|
CIC/ ICT
(children 6-71 months) |
abnormal
|
abnormal |
<20
|
³ 20 to <40
|
³ 40
|
Sources: All eye signs from John’s
notes Table 7 (? Get reference); Blood signs from Prevention of Micronutrient
Deficiencies Ch4: Prevention of Vitamin A Deficiency Table 4-2 by Barbara Underwood, 1998.
****
The following table presents some suggested cut-off points for determining
risk of VAD in populations. These recommendations are directly quoted from Barbara
Underwood in Prevention of Micronutrient Deficiencies, Chapter 4. These are said to be
only arbitrary cut-offs, but used to guide in identifying at risk populations.
Ecological and Illness related indicators
(Suggested Prevalence Cut-off for Determining VAD Risk For a Population)
| Indicator |
Suggested Prevalence Cut-off |
| Ecological indicators: Breast-feeding pattern
Children <6 months of age
Children ³ 6 – 18 months of age
Nutritional status (<-2 SD from WHO/ NCHS)
Stunting (H/A) (<3 years of
age)
Wasting (W/H) (<5 years of age)
Low Birth Weight (<2500 grams)
Food Availability
Market
Household
Dietary Patterns
Children 6- 71 months
Pregnant/ lactating women
Semi-Quantitative / Qualitative Food Frequency Questionnaire |
>50% not receiving breast milk
<75% receiving vitamin A foods in addition to breastmilk at least 3 times/week
³ 30%
³ 8%
³ 15%
DGLVs unavailable ³ 6 months/yr
<75% households consume vitamin A rich foods at least 3 times/week
<75% consume vit A foods at least 3 times/week
<75% consume vit A foods at least 3 times/week
Foods of high vitamin A content eaten <3 times/week |
| Illness related Indicators: Immunization coverage at 12 months
Measles Case Fatality Rate
Diarrhea Disease Rate (2-Wk Point Prevalence)
Fever Rates (2-Wk Point Prevalence)
Helminthic Infection Rates (especially ascaris) |
<50% fully immunized
³ 1%
³ 20%
³ 20%
³ 50% |
Source: Table 4-3A and Table 4-3C on p. 114 of Prevention of
Micronutrient Deficiencies Ch. 4: Prevention of Vitamin A Deficiency by Barbara Underwood,
Ph.D., National Academy Press, Washington D.C., 1998.
The following is a preview to the suggested assessments and action taken when
VAD is detected.
…Assessment
Assessing VAD, since clinical signs are somewhat rare, is to first assess risk through
dietary availability (e.g. seasonality) and dietary habits (for various age groups,
sexes). When using clinical eye signs (such as xeropthalmia, Bitot’s spots) in
preschool children there should be a large sample collected (say, 10,000), again since
they are somewhat rare and a later stage of vitamin A deficiency. If possible, it is more
effective to measure serum retinol, and since it is a sub-clinical measure it can detect
deficiency both at an earlier stage and in with a smaller sample size.
…Action
Provide vitamin A capsules (high dose) every 6 months for children > 6 months of age
Vitamin A capsules (high dose) should be given to mothers within 1 month of delivery and
breastfeeding (exclusive for 4-6 months, including colostrum "first milk")
should be promoted
Vitamin A capsules should be provided to children with measles, diarrhea, and other
illnesses
Advocate fortification of a staple food (usually a fatty food is best), such as oil, red
palm oil
Promote consumption of fruits and vegetables