A cross-sectional community based study was conducted at the national level in Ethiopia during February to May 2005, among women age 15 – 49 years. Women of this age group are recommended for the assessment of the severity of iodine deficiency and the link between iodine deficiency and poor pregnancy outcome because of their dramatic response to the inadequate intake of iodine.
Ethiopia, situated in the horn of East Africa, is mountainous where the top layer of the soil in many parts has been eroded for decades leading to leaching away of nutrient including iodine [15].
According to the Federal Ministry of Health of Ethiopia 2004 [16], the country's estimated population was more than 73 million. Majority, more than 85% are rural dwellers depending on subsistent agricultural economy. The staple crops are teff (Eragrostis tef) and cereals in the North and Central part, enset (Ensete ventricosum), cassava (Manihot esculenta), maize (Zea mays), cereals and root crops in the South and Southwest, and sorghum and maize in the East of the country.
Out of 11 regional states, 10 were included in the study. In one of the regions only regional capital and surrounding areas were assessed because other parts were inaccessible for security reason. In the selected cluster (a cluster is equivalent to the smallest administrative unit as defined by the Government and is commonly known as "kebele"), only women in child bearing age, married and volunteer to participate in the interview were included.
Multistage cluster sampling methods was applied to select study population. A total of 10998 women, thirty per cluster, were included in the study. Thirty clusters per regional state were selected by assigning probability proportional to the population size. In each regional state, cumulative populations were calculated and attributed number assigned. The sampling interval was then calculated by dividing the total number of study population with the number of clusters (thirty). A random number was drawn using a random number table. The first cluster selected based on this number. To select the others clusters the sampling interval was added sequentially to the random number till all thirty clusters were selected.
In four large and densely populated regional states namely Amhara, Oromia, Southern Nations Nationalities and peoples (SNNP) and Tigray, where more than 80% of the country's population live the study was conducted both in high and low land villages of the selected areas. The sample size taken in each of these regions was nearly twice that of the sample size in the rest of the states. The initial aim was to assess IDD in the two eco-zones independently. However, because of lack of separately delineated lowland and highland population; results were not compared by topography. Besides, in some of the regions due to non-respondents and security reason expected sample size was not obtained.
In each cluster households were selected by locating the centre of the locality/kebele and spinning a pen and proceeding to the direction that the pen pointed to. Household along the direction to the boundary of the locality was counted and numbered. A random number selected which determined the starting point, the first house selected, to examine and interview eligible women. Then the subsequent households in the identified direction were visited until thirty women per cluster were obtained for thyroid size estimation and interview. Those women who were not present at the time of the survey were revisited, interviewed and examined clinically for goitre.
Doctors and nurses were recruited and trained for one week to serve as data collectors. The training was focused on how to do standardized clinical examination of goitre and on interview techniques. Doctors were assigned to examine thyroid size of a group of subjects selected from goitre endemic village. The data from each examiner was compiled and the variation was assessed. The standardization procedure continued until inter-observer variation was negligible. In the actual study, team leaders did random counter checking on clinical examination everyday. Doctors undertook the clinical examination, and nurse the interviews.
Reproductive failure is defined as a history of having at least one or more miscarriage and or stillbirth. Retrospective information on reproductive failure and knowledge on IDD such as causes of goitre, health problems associated with goitre, importance of iodated salt, iodated salt handling and other health and demographic information were collected using structured household questionnaire. The nurses administered the questionnaire to women. Data were collected by house-to-house visit.
Supervisors who are responsible to coordinate and lead the overall activities reviewed the questionnaires on the spot to ensure completion and accuracy. Every evening survey group had meeting to discuss the experience of the day and plan for the next day.
Physical examination of the thyroid gland was done to assess goitre rate using the WHO/UNICEF/ICCIDD classification scheme [17] as follows:
Grade 0: None or no goitre (palpable or visible)
Grade 1 or palpable: A goitre that is palpable but not visible when the neck is in the normal position, (i.e. the thyroid is not visibly enlarged).
Grade 2 or visible: A swelling in the neck that is clearly visible when the neck is in a normal position and is consistent with an enlarged thyroid when the neck is palpated.
Total Goitre Rate (TGR): Sum of goitre grades 1 and 2.
Data was entered into a computer and analyzed using SPSS for windows, version 10, 1997. X2 – test was used to assess level difference in reproductive failure between high (seven) and less endemic (three) regions. The grouping of endemic regions was done based on the median urinary iodine level determined by another component of the study (reference 14). Accordingly 7 of the 10 regions studied were grouped to high and the remaining 3 to low endemic regions
Similarly history of reproductive failure was compared between goitrous and non goitrous women. Goitre prevalence of each regional state was weighted according to total population size of the region. Then the overall (national weighted rate of goitre with 95% confidence interval (CI) was given to make regional distribution of goitre nationally representative.
Informed consent
In each regional state, regional administration approved this study. All women gave their informed consent prior to their inclusion in interview and clinical examination.