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Brief Research Article
Goiter Prevalence, Urinary Iodine, and Salt Iodization Level in Sub-Himalayan Darjeeling District of West Bengal, India Akhil Bandhu Biswas1, *Dilip Kumar Das2, Indranil Chakraborty3, Asit Kumar Biswas4, Puran Kumar Sharma5, Romy Biswas6 1
Professor, Department of Community Medicine, Institute of Health and Family Welfare, Kolkata, 2Professor, 6Associate Professor, Department of Community Medicine, North Bengal Medical College, Darjeeling, 3Professor, Department of Biochemistry, Maldah Medical College, Maldah, 4Technical Officer, SPSRC, Department of Health and Family Welfare, 5 District Maternal and Child Health Officer, Dakshin Dinajpur District, West Bengal, India
Summary National iodine deficiency disorders control program needs to be continuously monitored. Hence, a cross-sectional study was conducted during the period from April-May 2011 to assess the prevalence of goiter, status of urinary iodine excretion (UIE) level and to estimate iodine content of salts at the household level in Darjeeling district, West Bengal. Study subjects were 2400 school children, aged 8-10 years selected through “30 cluster” sampling methodology. Goiter was assessed by standard palpation technique, UIE was estimated by wet digestion method and salt samples were tested by spot iodine testing kit. Overall goiter prevalence rate was 8.7% (95% confidence intervals = 7.6-9.8) and goiter prevalence was significantly different with respect to gender. Median UIE level was 15.6 mcg/dL (normal range: 10-20 mcg/dL). About 92.6% of the salt samples tested had adequate iodine content of ≥15 ppm. Findings of the present study indicate that the district is in a transition phase from iodine-deficiency to iodine sufficiency.
Keywords: Goiter, Iodine deficiency, Iodized salt, Urinary iodine
Iodine deficiency leads to a spectrum of health consequences collectively known as iodine deficiency disorders (IDD). IDD is one of the major public health problems in India, including West Bengal.1,2 Wide spread distribution of environmental iodine deficiency is increasingly being evident not only in Himalayan regions, but also in the sub Himalayan Terai areas, riverine areas subjected to flooding and the coastal regions.2 *Corresponding Author: Dr. Dilip Kumar Das, Professor, Department of Community Medicine, North Bengal Medical College, Darjeeling, West Bengal, India. E-mail:
[email protected]
Access this article online Website: www.ijph.in DOI: 10.4103/0019-557X.132291 PMID: 24820989
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In this country, an estimated 200 million people are at risk for IDD. Of these, 71 million have goiter, 2.2 million suffer from cretinism and 6.6 million have neurological deficits.3,4 The National Iodine Deficiency Disorders Control Program is being implemented in India with the goal of virtual elimination of IDD. However, it is necessary to monitor the progress of the program using recommended quantifiable indicators5 at the state/ district level. During the last few years, 7 out of 19 districts of West Bengal were surveyed to assess the status of IDD using the suggested methodology. All the districts were found to be endemic for IDD.6-12 The status in other districts of the state was not known to the program managers. Hence, the present assessment was done in Darjeeling district with the objectives of assessing the prevalence of goiter among school children aged 8-10 years; determining the urinary iodine excretion (UIE)
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Biswas, et al.: Iodine Deficiency in a Sub-Himalayan District, India
levels of the study subjects and the iodine content of salts at the households level. The observational cross-sectional study was conducted during April-May 2011 in sub Himalayan Darjeeling district of West Bengal. The study subjects were school children aged 8-10 years. Children aged 6-12 years are recommended for assessment of IDD because of their combined high vulnerability to disease, easy accessibility and representativeness. However, it is generally feasible that children of 8-10 years of age be studied in a school based approach.5 In addition, the earlier studies in seven districts of the state6-12 have also been conducted among 8-10 years aged school children, thus the status can also be appropriately compared. There was no available information on the prevalence of goiter in Darjeeling district. Thus considering an assumed prevalence of 50%, confidence interval of 95%, design effect of 3 and relative precision of 10% the calculated sample size was 1200. But as our intention was to assess the degree of severity also, double the calculated size was felt to be adequate.5 Thus, the final sample size was 2400 i.e., 80 school children per cluster in 30 cluster sampling technique. Firstly “30 clusters” (i.e., villages/wards) were selected through multistage cluster sampling based on “probability proportional to size.” In each identified cluster, of the entire primary schools one was randomly selected. All children between 8 and 10 years of the selected school were enlisted from school records and 80 children were included in the study. Wherever the sample size could not be covered in the selected school, an adjoining school was included to complete the required number in each cluster. Thus, finally a total of 2400 (80 × 30) study subjects were surveyed. Ethical approval was obtained from the institutional ethics committee of I.D and B.G. Hospital, Kolkata, West Bengal. Before actual data collection, district health and primary school authorities, headmasters/ headmistresses of the identified schools were briefed and sensitized about the study. Through the school authorities parents of the students were informed and necessary consent obtained. School authorities were requested to ensure maximum attendance of the students on the day of the survey.
Trained investigators (faculty members of community medicine, North Bengal Medical College and Public Health Specialists) recorded relevant data in a predesigned and pretested proforma. Assessment of goiter, urinary iodine and salt iodine were done as detailed below: Goiter was assessed clinically by standard palpation methodology. Grading was done according to the criteria recommended by the joint WHO/UNICEF/ICCIDD5,13 into three categories (Grade 0: No palpable or visible goiter. Grade I: Palpable but not visible goiter. Grade II: Visible goiter). The sum of goiter Grade I and II Was considered as total goiter rate (TGR). Severity of IDD was interpreted based on the criteria of goiter prevalence in school aged children as suggested by WHO/UINCEF/ ICCIDD.5 The recommended sample size for collection of biological specimen like urine is 300 (10 children × 30 clusters).13 Considering 20% dropout/wastage, final sample size of urine samples was 360 i.e. 12 children × 30 clusters. Casual on the spot urine samples were collected by systematic random sampling from the school children, who were examined for assessment of goiter. Urine samples were collected in wide-mouthed screw-capped plastic bottles (one drop of toluene was added to prevent bacterial growth and minimize odor) and transported to the laboratory in an ice-packed transport-container. In the laboratory samples were preserved in recommended temperature until processing to prevent any pre-analytical error. Two urine samples were discarded and thus 358 samples could be analyzed. Urinary iodine level was determined by wet digestion method14 following the recommended guidelines and maintaining internal quality control having a known concentration range of iodine content with each batch of test samples. As a part of quality control, within batch and between batches precision were determined. The results were expressed as mcg iodine/dL urine. The faculty members of the Department of Biochemistry, Medical College, Kolkata did the biochemical estimation of urinary iodine. All the study children in each cluster were asked to bring about 20 g of salt in auto seal polythene pouches, which were routinely being consumed in their respective families. Iodine content of 2400 salt samples was determined by spot iodine testing kit (produced by MBI chemicals, Chennai, India). The iodine content was
Indian Journal of Public Health, Volume 58, Issue 2, April-June, 2014
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estimated semi quantitatively and expressed in three categories: 0,
