We read with interest the recent communication on the prevalence of
Vitamin A deficiency (VAD) among rural preschool children of West Bengal
, and urge caution in extrapolating the VAD burden because the survey
methodology was prone to overestimating the magnitude of deficiency.
Night blindness was also assessed between 12 and 24
months of age: The presence of night blindness cannot be
reliably identified among children between the ages of 12 and 24 months.
The World Health Organization (WHO) has therefore recommended that the age
group of 24-71 mo should only be included for assessment of night
blindness amongst children .
Conjunctival xerosis (X1A) as an independent indicator
of VAD: VAD is only one of the several causes of conjunctival xerosis;
thus the reliability of this sign (X1A) for independent assessment of VAD
in field conditions is questionable [3,4]. Conjunctival xerosis is
clinically expressed as marked dryness or unwettability; the affected area
appears roughened, with fine droplets or bubbles on the surface, rather
than smooth and glistening. These changes are best detected in oblique
illumination and the abnormalities are often overlooked or, in apparent
overcompensation, over-diagnosed. Thus, changes in the conjunctival
xerosis by themselves are not an accurate basis for estimating prevalence
of clinical xerophthalmia [2,3].
Interpreting serum retinol estimates: According to
WHO , a major disadvantage of using serum retinol concentration as an
indicator of vitamin A status is that retinol concentrations are decreased
by acute and underlying chronic infections. The authors did not report
simultaneous serum C reactive protein levels to detect overt or
subclinical infections for an apt interpretation. Serum retinol
concentrations are under homeostatic control over a broad range of body
stores and may reflect body stores content only when it is very low or
very high. Further, the WHO concludes that there is no direct evidence of
the serum cut-off value where functional consequences including morbidity
and mortality effects, begin to occur . No data has been provided to
reassure that the dried blood spot on filter paper did not underestimate
the serum retinol levels due to transport conditions.
In view of the declining trend of VAD in several
regions of the country, it would have been pertinent to state the year of
the survey to put the findings in true perspective. It would also be
prudent to caution that these overestimates from the poorest segment of
population are not inadvertently extrapolated to the entire state for
1. Arlappa N, Balakrishna N, Laxmaiah A, Nair KM,
Brahmam GN. Prevalence of clinical and sub-clinical vitamin A deficiency
among rural preschool children of West Bengal, India. Indian Pediatr.
2. Report of a joint WHO/UNICEF consultation. Geneva,
World Health Organization, 1996 (Review version, WHO/NUT/96.10).
3. Sommer A. Vitamin A deficiency and its consequences:
A field guide to detection and control. Geneva: WHO; 1995.
4. Reddy V, Rao V, Reddy M. Conjunctival impression
cytology for assessment of vitamin A status. Am J Clin Nutr.