Key to the data tables for the Database on Vitamin A Deficiency
The most recent survey information for each country is displayed at the top of the data tables, followed by earlier surveys if available. Within each survey, data for the total population surveyed (Total) are displayed first. Disaggregated data are displayed thereafter by physiological status, sex, age, area or region.
The following abbreviations are used to describe survey administrative levels:
N = National
R = Regional
S = State
D = District
L = Local
Surveys carried out exclusively in urban and rural areas are specified by adding a U or R to the administrative level. For example, NU stands for National Urban and DR stands for District Rural.
The date field reflects the year(s) during which the survey took place. If no date was specified for the survey, the date of publication is used and a P is inserted next to the date, for example, 1999P.
Location and sample descriptor
This field describes the location of the survey and the sample itself, that is, the specific population surveyed.
The sex of the population surveyed. If no sex is specified, it is assumed that both sexes were studied.
B = Both
F = Female
M = Male
The age of the population surveyed expressed in years. If age is not specified, the abbreviation NS is used.
The sample size of population investigated. The abbreviation NS (not specified) is used when the sample size is not provided in the survey report.
The prevalence (%) of the population surveyed with xerophthalmia.
Current XN = Current night blindness
Previous XN = This is night blindness during a previous pregnancy,the time period for each survey is provided in the general notes
X1B = Bitot's Spots
X2 = Corneal Xerosis
X3A = Corneal ulceration/ keratomalcia <1/3 corneal surface
X3B = Corneal ulceration/ keratomalcia >/= 1/3 corneal surface
XS = Corneal scar
The prevalence (%) of the population surveyed with a retinol concentration below a cut-off. The cut-off levels: 0.35, 0.70, 1.05 µmol/L are the most frequently used to assess vitamin A status.
The mean retinol concentration in serum or plasma expressed in µmol/L.
The SD (standard deviation) of the mean retinol concentration expressed in µmol/L.
The method used to measure retinol concentrations are coded as follows:
A = High Perfomance Liquid Chromatogrophy (HPLC)
B = Spectrophotometry (de Bessy and Lowry)
C = Colorimetry (eg. Carr-Price method)
D = Fluorescence
E = Other (Specific method mentioned in survey notes)
NS = Not specified
References for each country are shown at the bottom of the data table categorized as:
- Data references: references for which data are presented.
- Additional references: references providing additional information on vitamin A status for the country in question.
Letters following the reference numbers refer to different surveys within the same reference.
General notes provide additional information applying to the entire survey (for example details on the survey design) and are presented at the bottom of the data tables. General notes indicated by an asterisk (*) in the table.
Line notes provide additional information to the data found in a specific line. Details are given at the bottom of the data tables.
The following abbreviations were used in the "Location and sample descriptor", "General notes" or "Line notes" columns:
LW = Lactating women
NPNLW = Non-pregnant, non-lactating women
NPW = Non-pregnant women
Pre SAC = Preschool-age children
PW = Pregnant women
PPS = Probability proportionate to size
SAC = School-age children
SD = Standard deviation