Assessing status of Iodine Deficiency Disorders in Ramanagara District

INTRODUCTION

Iodine deficiency is a major nutrition problem in India. Iodine deficiency leads to a wide spectrum of disorders commencing with the intrauterine life extending through childhood and adult life with serious health and social implications.1 Lack of Iodine in the diet leads to visible and invisible spectrum of health consequences collectively called iodine deficiency disorders (IDDs).2 Iodine Deficiency Disorder (IDD) constitutes the single largest cause of preventable brain damage worldwide leading to learning disabilities and psychomotor impairment.3 It was estimated that 1.9 billion people from 130 countries are at risk of developing IDD. Globally, India has the largest number of children born vulnerable to iodinedeficiency.4 In India also, IDD has been identified as a public health problem with 200 million people at risk.5

Two major factors responsible for IDD are inadequate iodine intake and inadequate iodine utilization. The inadequate iodine intake may be secondary to low iodine content of the soil or inadequate iodine consumption of sea food due to high cost and low availability.6

In India, IDDs have been in existence since centuries yet continue to be a major health problem. The simplest, the most effective and inexpensive mode recognised to prevent the broad spectrum of IDD is to consume iodized salt daily.7

However, globally, India has the largest number of children vulnerable to iodine-deficiency. Of the 325 districts surveyed in India, 263 districts are IDDendemic, i.e. the prevalence of IDD is above 10 per cent in the population.4 The Government of India launched National Goitre Control Programme (NGCP) in 1962 which was later renamed as the National Iodine Deficiency Disorders Control Programme (NIDDCP). The goal of the program was to reduce the prevalence of IDDs to below 10 percent in endemic districts of the country by the year 2000. In order to eliminate iodine deficiency in India and to comply with the international goal of universal iodization, compulsory iodization of all table salt was introduced in 1983 and sale of non-iodinated salt for direct human consumption was banned in the entire country in 2006.8

As reported by the Indian Council of Medical Research, significant progress has been made by NIDDCP; 15 districts of 11 states showed a goitre prevalence of less than 5% in 2016.9 However, few studies done in South Karnataka indicated that few districts are endemic for goitre with a total goitre prevalence of 15.2% to 27.5% in 2008-09. The programme emphasizes on the periodic evaluation and assessment of IDD situation. Thus, it is recommended that prevalence surveys should be conducted every 5 years along with measurement of urinary iodine levels and analysis of salt iodine content among school children aged 6-12 years.10

Hence, this study was undertaken to track the progress made towards reducing the burden of iodine deficiency diseases in the Ramanagara district.

MATERIALS AND METHODS

A cross sectional study was conducted in Ramanagara district during the month of February to April 2019 by the Departments of Community Medicine and Biochemistry, Bangalore Medical college and Research Institute, Bengaluru.

The total population of the Ramanagara is 10,44,454 and encompass an area of 308sq km with four talukas namely, Ramanagara (Population 2,46,600; 24% of the total), Channapatna (Population 2,60,314; 26% of the total), Kanakapura (Population 3,31,934; 35% of the total) and Magadi (Population 2,55,616; 25% of the total). It has 6 towns with 90 villages and 68.3% of the total population is urban.10

There are 712 schools in the Ramanagara with 1,80,464 students enrolled in 1st to 8th standards, majority being in the age group of 6-12 years. At any given point of time we had expected less than 5-10 percent of absentees from schools.10

Children in the age-group of 6-12 years were selected from 30 schools (112 from each school) in the 4 taluks of Ramanagara using the technique of Population Proportionate to Size (PPS) sampling. As the school attendance in Ramanagara was more than 90%, the sample was restricted only to the school children.

Sample size was calculated using the following formula

n = 1.962p(1-p) (DEFF) / d2

With assumed proportion p= 0.50, 1-p= 0.50; desired level of precision, d= ±5% and design effect, DEFF=2, the estimated sample size was 2700.

Multi-stage cluster sampling with population proportional to size as recommended by NIDDCP was used.11 The sampling frame comprised of cumulative population of each village/ ward (cluster) of the 4 taluks of Ramanagara. Schools were selected from the respective communes of each taluka. A total of 30 units(schools)were selected by systematic random sampling using PPS. Of these 30 units, 9 schools were from Ramanagara, 7each from Channapatna, Kanakapuraand Magadi. A list of all schools (primary, middle, secondary and higher secondary schools) was made showing the total number of enrolled children. Each school was selected from each selected cluster by simple random sampling. About 112 children; 56 boys and 56 girls aged between 6-12 years were selected from Class I to Class VII by systematic random sampling. Equal representation in each gender and age category was ensured.

The study was initiated after approval from the Institutional Research Committee and Institutional Ethical Committee. The study was funded by State IDD cell under NHM. Prior permission was obtained from the Director of Health & Family Welfare Services and Director of Education, Ramanagara. The school Headmasters were contacted and informed about the survey and their consent was obtained. Informed consent forms both in Kannada and English were sent to the parents of the selected students with the help of the school Head Masters and teachers. All those children below 6 years or above 12 years as per the records in the school were excluded from the study. A pre-designed and pre-tested proforma was coded in to google questionnaires used to record demographic and physical examination findings of the students.

Each selected child was examined clinically by a research team comprising of trained postgraduates and interns under the supervision of a faculty from the department of Community Medicine. Training was imparted to the Postgraduates and interns involved in the project by the Investigators. Examination for goitre was done by palpatory method and classified as Grade 0, 1 and 2 according to the prescribed guidelines of NIDDCP and WHO/ UNICEF.

Spot urine samples were collected from every 10th selected student in a labelled wide mouthed screw capped plastic container of 50 ml capacity. The samples were transported to the clinical biochemistry lab of BMCRI for processing and for quantitative estimation of iodine in urine, using the method based on Sandell-Kolthoff reaction. For school aged children an adequate iodine intake was defined as a median urinary iodine level in the range of 100-299 micrograms/litre.

One of the indicators for sustainable elimination of IDD is to have fewer than 20% of school-age children with urine specimens having an iodine concentration of less than 100micrograms/ litre. Every 5th selected child was given an airtight self-sealing plastic pouch to bring a spoonful salt consumed by their families from their homes. These samples were tested using standard iodometric titration method. Iodine concentration was recorded and a value of > 15ppm was considered adequate.

For operational feasibility, it was decided to select two students (1 boy, 1 girl) from each class to give urine samples for analysis and four students (2 boys, 2 girls) from each class for salt sample testing ensuring that the sample size requirements are met.

A list of all children with goitre (grade 1 & 2) identified was provided to the Principal of the respective schools, so that necessary action like intimating the parents and referral for further management can be undertaken. During the survey, a health awareness programme on IDD was conducted for the school children, teachers and staff.

The presence of Goiter was graded using WHO Classification as follows,

Grade 0 – No palpable or Visible Goiter

Grade 1 – Palpable but not visible Goiter

Grade 2 – Palpable and Visible Goiter

Assessment of urinary iodine was done by an assay based on the Sandell-Kolthoff reaction.

The Children were divided into groups according to urinary iodine levels.

<20µg/L – Severe iodine deficiency

20-49µg/L- Moderate iodine deficiency

50-99µg/L – Mild iodine deficiency

≥100µg/L – Iodine replete state

Household salt samples were analysed for its iodine content using standard iodometric titration method.

A total of 2700 children comprising 1336 males and 1364 females were enrolled for the study. The investigators and postgraduates were trained regarding the examination and grading of Goiter, collection of salt sample and urine sample from the selected children.

RESULTS

A total of 2700 children from 30 schools were screened for thyroid enlargement. About 308 Urine sample were collected; of which only 270 (10%) were analysed for urinary iodine concentration. Other samples were discarded due to low quantity, sediments or turbidity. Salts from 540 (20%) households were titrated for iodine content. The list of schools selected for the survey is mentioned in annexure II & III.

Among 2700 students examined 1336 (49.4%) were boys and 1364 (50.6%) were girls. Among them 741 (27.4%) belonged to age group of 6-7 years, 672 (24.9%) of age group 8-9 years, 691 (25.6%) of age group 10-11 years and 596 (22.1%) of age group 12 years

Among the examined 2700 students 353 (13.1%) had Goiter. Out of which 57 (2.1%) had Grade 2 Goiter. Majority of the boys 207 (58.7%) were having Goiter. The children belonging to 8 to 9 years 107 (30.3%) were having Goiter majority among the students.

Analysis of iodine levels in 540 household salt samples showed that all the samples were adequately iodized with iodine content of >15 ppm. Iodine concentration in salt samples was in the range of 35.66 to 178.33 ppm with a median concentration of 71.332 ppm.

A total of 270 urine samples were collected and analysed for urinary iodine excretion (UIE). Range of UIE was 0-115 µg/L. 18 (6.7%) of the study participants had UIE below 20µg/L. 24 (8.8%) of them had UIE between 21-49µg/L. 46 (17.1%) of the children had UIE concentration from 50-99µg/L. More than half of them, 182 (67.4%) had UIE above 100µg/L. Median UIE was found to be 78.3µg/L, suggesting IDD to be a mild public health problem in Ramanagara district.

Discussion

The prevalence of endemic goiter in school children in the age group of 6 to 12 years is the most widely accepted marker to evaluate the severity of IDD in a region. It is an index to the degree of long-standing iodine deficiency and actually indicates the long-term iodine nutritional status in a population. In our study, overall prevalence of goiter was found to be 13.1%. According to the WHO recommendations, an area with prevalence rate of 5.0 to 19.9% is considered as mildly endemic, whereas areas with prevalence rate of 20 to 29.9% and > 30% are considered as moderately and severely endemic for goiter respectively.12 This suggested that IDD is a mild public health problem in this region.

Urinary iodine excretion is an important biochemical marker for the assessment of IDD as 90% of iodine excretion is through urine.13 Urinary iodine excretion indicates very recent iodine intake and is an index of choice for evaluating the degree of iodine deficiency and its correction. The WHO recommends that at least 50% of population achieving UIE of 100 µg/L and not more than 20% of the samples below 50 µg/L in an area indicates iodine-replete status among population.14 Median UIE level in our study was 78.3 µg/L and 67.4% of the total studied population had urinary iodine levels ≥ 100 µg/L, indicating that there was no biochemical iodine deficiency. Similar results were found in one population-based study done in Cochin.15 In this study, UIE was estimated in 954 adult subjects and median iodine excretion value was reported as 211 µg/L, suggesting that the population was iodine sufficient.

The WHO recommends that 90% of the household salts should get iodized at the recommended level of 15 ppm,16 but our study showed that only 100% households were consuming adequately iodized salt. A study conducted by Dhaar et al.17 also reported that 73.15% of 18,011 salt samples analyzed confirmed to the prescribed standards. This indicates that even if iodine nutrition seems to be appropriate by optimal UIE levels at this point of time, still it is possible that iodine deficiency can emerge as public health problem in future.

A study conducted by Kapil et al.18 in Delhi showed similar results where 88.7% of the study population had more than 100 µg/L and 2.6% had less than 50 µg/L daily UIE. In their study, 16% of families were consuming salt with iodine content < 5 ppm as compared to our study where no family was consuming salt having iodine content < 5 ppm. During 1994 to 2002, Human Nutrition Unit, AIIMS, collected a total of 24,798 salt samples from various research surveys from more than 160 districts of 13 states of the country. These salt samples were analysed using the standard iodometric titration method. Their findings indicated that the salt iodization in India was within the safe limits.19

However, Patro et al.20 in their study concluded that adequate salt iodization in Jharkhand was only 64.2% but total goiter rate was 0.9% only with median UIE of 173.2 µg/L. Another study conducted by Das et al.14 in West Bengal reported TGR 13.7% and median UIE level of 130 µg/L and 80% salt samples having adequate iodine content.

The results of our study also point toward changing pathogenesis of goiter to immunological, hereditary, or infectious causes. Also, in India, large numbers of cyanogenic plants are used as common vegetables and thus IDD persists in many regions in spite of recommended iodine intake. Indian cyanogenic plant foods have potential antithyroid activity and supplementation of extra iodine fails to counteract their effect.21 In this region, people also consume vegetables of Brassica family, spinach, and others, which have presence of goitrogens that can interfere with iodine metabolism by competitive inhibition of iodide transport into the thyrocyte. Biswas et al.22 found a significant positive correlation between urinary iodine and urinary thiocyanate concentrations suggesting that when consumption of thiocyanate is increased as evidenced by increased urinary thiocyanate levels, the excretion of iodine almost increased proportionally.

CONCLUSION

Considering prevalence of Goiter in 6-12 years children, Ramanagara district of Karnataka is an Endemic district for Iodine deficiency disorder. IDD is a mild public health problem in Ramanagara district as inferred from median UIE cut-offs. House hold level salt is adequately iodised as per NIDDCP recommendations. It is recommended that intensified information, education, and communication activities, along with further strengthening the system of monitoring the quality of iodized salt provided to the beneficiaries should be continued to progress toward elimination of IDD.

Limitations of the study:

1. All students were examined for the presence of goitre but salt iodine testing and urine iodine testing was done for every fifth and tenth child. Testing for salt iodine and urine iodine in children with grade 1 or 2 goitre may indicate the causal factors for goitre in that child.

2. A subset of the selected students were asked to bring salt samples from their homes for testing for iodine levels. Many households have reported consumption of both common salt and rock salt; but the salt sample testing was done only for one sample that was brought by the students. This may not give the accurate picture of the pattern of consumption of iodised salt in the community.

3. As the adolescent boys/girls due to hormonal changes the thyroid gland may enlarged. To be ruled out by specific test like T3, T4, TSK.