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BRIEF RESEARCH ARTICLE
Year : 2014  |  Volume : 58  |  Issue : 2  |  Page : 129-133  

Goiter prevalence, urinary iodine, and salt iodization level in sub-Himalayan Darjeeling district of West Bengal, India


1 Professor, Department of Community Medicine, Institute of Health and Family Welfare, Kolkata, West Bengal, India
2 Professor, Department of Community Medicine, North Bengal Medical College, Darjeeling, West Bengal, India
3 Professor, Department of Biochemistry, Maldah Medical College, Maldah, West Bengal, India
4 Technical Officer, SPSRC, Department of Health and Family Welfare, Dakshin Dinajpur District, West Bengal, India
5 District Maternal and Child Health Officer, Dakshin Dinajpur District, West Bengal, India
6 Associate Professor, Department of Community Medicine, North Bengal Medical College, Darjeeling, West Bengal, India

Date of Web Publication12-May-2014

Correspondence Address:
Dr. Dilip Kumar Das
Professor, Department of Community Medicine, North Bengal Medical College, Darjeeling, West Bengal
India
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Source of Support: Department of Health and Family Welfare, Government of West Bengal., Conflict of Interest: None


DOI: 10.4103/0019-557X.132291

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   Abstract 

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


How to cite this article:
Biswas AB, Das DK, Chakraborty I, Biswas AK, Sharma PK, Biswas R. Goiter prevalence, urinary iodine, and salt iodization level in sub-Himalayan Darjeeling district of West Bengal, India. Indian J Public Health 2014;58:129-33

How to cite this URL:
Biswas AB, Das DK, Chakraborty I, Biswas AK, Sharma PK, Biswas R. Goiter prevalence, urinary iodine, and salt iodization level in sub-Himalayan Darjeeling district of West Bengal, India. Indian J Public Health [serial online] 2014 [cited 2019 Sep 17];58:129-33. Available from: http://www.ijph.in/text.asp?2014/58/2/129/132291

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]

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 indicators [5] 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],[7],[8],[9],[10],[11],[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) 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 state [6],[7],[8],[9],[10],[11],[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/ICCIDD [5],[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 method [14] 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 estimated semi quantitatively and expressed in three categories: 0, <15 ppm and ≥15 ppm.

Data were entered in the Microsoft Excel and analyzed to find out the outcome variables. The χ2 and Z tests were applied as and when applicable and P < 0.05 was considered to be statistically significant.

[Table 1] depicts the prevalence of goiter by age and gender. Overall total goiter prevalence rate (TGR) was found to be 8.67% (95% confidence intervals = 7.6-9.8). Prevalence of Grade I and Grade II (visible) goiter was 8.08% and 0.58%, respectively. TGR was higher among girls than boys (10.54% vs. 7.05%; χ2 = 9.16, P = 0.000). Overall age specific TGR among 8, 9 and 10 years old children were 7.84%, 7.85%, and 10.24% respectively; the difference was not statistically significant (χ2 = 3.91, P = 0.141).
Table 1: Goiter prevalence by age and gender in Darjeeling District, West Bengal (n = 2400)

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The median UIE level was found to be 15.6 mcg/dL (range: 0.84-36.2 mcg/dL). 99.16% (355/358) urine samples had UIE above the recommended level of ≥10 mcg/dL. Only one (0.28%) child had urinary iodine level in the severe range (<2 mcg/dL) and 2 (0.56%) children had mild range (5-9.9 mcg/dL) of iodine deficiency in the district [Table 2].
Table 2: UIE levels in the study population in Darjeeling District, West Bengal (n = 358)

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In the present study, 2400 salt samples were tested with spot iodine testing kit. 92.6% (2223/2400) of the salt samples had adequate iodine content of ≥15 ppm. 5.6% (134/2400) had iodine content of <15 ppm and only 1.8% (43/2400) had no iodine content.

Further analysis revealed that the proportion of households consuming adequately iodized salt in rural areas (90.6%, 1531/1689) was significantly lower than urban areas (97.3%, 692/711; Z = 7.16, P < 0.05).

The WHO/UNICEF/ICCIDD have recommended that if <5% school children (6-12 years) have goiter, the area should be classified as endemic to iodine deficiency. [5] The present study with goiter prevalence of 8.7% signifies that the district is mildly endemic for iodine deficiency. Almost identical prevalence (8.8%) was reported by a recent study in Gujrat. [15] However, earlier studies in seven districts of the state viz. Malda, Birbhum, Dakshin Dinajpur, North 24 Parganas, Purulia, Howrah and Purba Medinipur revealed a higher prevalence of 11.3%, 12.6%, 18.6%, 20.1%, 25.9%, 13.7% and 19.7% respectively. [6],[7],[8],[9],[10],[11],[12] In contrast to all other districts studied so far in West Bengal, Darjeeling district had a lower TGR of even <10%.

However, at the national level a TGR of >5% was found in 9 out of 15 districts studied in 11 other states by an Indian Council of Medical Research study team. [16] No district in West Bengal yet reported such a desired level of prevalence.

Urinary iodine concentrations are the most useful indicator of IDD and it has been recommended that no iodine deficiency is indicated in a population when median urinary excretion level is ≥10 mcg/dL, i.e., <50% of the urine samples have UIE level of ≥10 mcg/dL and not >20% of the samples have UIE level of <5 mcg/dL. [5]

In Darjeeling district, all these indicators were within the acceptable range [Table 2] indicating that the district is currently having no iodine deficiency. This might be the positive impact of successful implementation of universal salt iodization in the district.

Similar findings of median UIE were reported in other districts of West Bengal [6],[7],[8],[9],[11],[12] and also by studies across the country in other states. [15],[17],[18],[19],[20] However, only three districts in other states [16] and one district (Purulia) in West Bengal [10] so far reported median UIE value less than the recommended level.

Iodine content of salts in the district was satisfactory; households consuming adequately iodized salt (92.6%) was more than the recommended goal of >90% coverage. [5] This might be the reflection of high level of awareness through information, education and communication activities in the district. None of the other seven districts [6],[7],[8],[9],[10],[11],[12] surveyed so far in the state reported such a desired level; rather consumption was alarmingly much lower in some districts. [7],[8],[9],[10] However, recent studies in other states [18],[20] reported >90% households consuming adequately iodized salts.

For monitoring progress toward the elimination of IDD, the recommended parameters are to be interpreted cautiously because UIE level reflects the current iodine status, while the prevalence of goiter indicates the long-term iodine status in a population. Findings of high TGR and optimal UIE have been reported in many studies in India [6],[7],[8],[9],[11],[12],[15],[16],[17],[18],[19],[20] reflecting a transition from iodine deficient to iodine sufficient state. Observation in Darjeeling district also corroborates with findings of those studies indicating that the district is also in a transition phase from iodine deficiency to iodine sufficiency. This process of transition needs to be augmented towards successful elimination of IDD with sustained consumption of adequately iodized salt, intensified awareness activities and an appropriate monitoring system.

We acknowledge the support and cooperation of the district authorities, Department of Health and Family Welfare as well as Department of Primary Education, Darjeeling district, West Bengal. We also express our sincere gratitude to the Department of Health and Family Welfare, Government of West Bengal for providing financial assistance and other support to carry out the study smoothly.

 
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    Tables

  [Table 1], [Table 2]


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