Epidemiology of Tuberculosis in Ardabil Province, 2011-2016

Department of Community Medicine, Faculty of Medicine, Ardabil University of Medical Science, Ardabil, Iran; firouz.amani@arums.ac.ir Department of Internal Medicine, Faculty of Medicine, Ardabil University of Medical Science, Ardabil, Iran; a.zakeri@arums.ac.ir Ardabil TB Register Center, Ardabil University of Medical Science, Ardabil, Iran; msadeg75@yahoo.com Department of Neurology, Faculty of Medicine, Ardabil University of Medical Science, Ardabil, Iran. v.abbasi@arums.ac.ir Department of Infection Disease, Faculty of Medicine, Ardabil University of Medical Science, Ardabil, Iran; j.mohammadshahi@arums.ac.ir


Introduction
Tuberculosis (TB) is a common cause of death due to Single-agent infectious diseases in world and despite the advances in medical science; it remains a health problem in many countries. TB is occurring due to Mycobacterium Basil and usually enters to body during infancy. By over time and also due to weakening of the immune system, Bacilli were multiplying and cause recurrence of the disease. TB had the 10 th rank in burden of diseases and it predicted that till 020 it reaches to 7 th rank.
According to the report of WHO in year 2011 the total cases of TB was 14.8 million and yearly about 9.3 million suffer to TB and 18 million die due to TB.
According the report of Iran ministry health, yearly 14.4 cases per 100000 suffered to TB. The incidence of extra-pulmonary in Iran from 2011 with 4.16 per 100000 decreased and reaches to 3.2 per 100000 in 2016 (2555 cases). About one-third of people with AIDS are associated with tuberculosis and this rate in Mediterranean was 23%. The HIV infection increase the risk of TB activation more than 10 times and according to the WHO in year 2011 about 13% of TB patients also had HIV. Tb could infect whole organs of the body, but the common form of TB is pulmonary that in adults, it is usually accompanied with smear positive sputum and highly contagious. TB appears in 85% of cases by pulmonary form and rest of them by extra-pulmonary form. Khazaei et al., in a study on 440 TB patients with smear positive sputum found that the median time for negative result of smear sputum in patients was 3 months. In the end of second month, smear sputum in 69% of patients was negative and this rate reach to 88% in the end of third month 1 .
One of the Millennium Development Goals (MDGs), was decreasing the rate of death due to TB in 2015 to half of 1990 death rate. Because of Iran's neighbors with Pakistan and Afghanistan countries and also due to the higher rate of TB in these countries, the risk of suffering to TB in our country is high and Iran had the 17 th rank in the world 2 .
Gupta et al., in a study found that factors such as smoking, Alcohol consumption, liver and kidney diseases, mall-nutrition and history of TB in family are effective factors 3 .
Heshmati et al., in a study showed that 74.7% of TB patients are in the form of pulmonary and most of extrapulmonary cases were lymph nodes with 3.3% 4 .
Shaghafipour et al., in a study during 2003-2010 found that 71.9% of pulmonary TB cases were positive smear and rest of the negative smear 5 .
In a study done by Hazrati et al., in Ardabil in 2005-2010 results showed that the TB total incidence rate was 8.54 per 100000 in Ardabil city and 56.2% of patients have pulmonary TB and rest of them have extra-pulmonary TB 6 .
Salek et al., in a study showed that the incidence of positive smear pulmonary TB decreased 4 times and also the rate of other TB cases decreased. Until age 10 year, there wasn't difference between two sexes but in age groups 10-14, the rate of incidence in girls was 2 times boys. Also, they found that this reduction can be related to improve the care system and health promotion 7 .
Beyramvand et al., in a study in 2014 showed that the simultaneous incidence of HIV infection and tuberculosis in the southwest of Iran was high 2 .
Study the epidemiology of TB during time and identify of disease trends and its changes in over time can be great importance in implications and achieve to using strategies for control disease, improve health and health promotion. The aim of this study was to investigate the epidemiological situation of tuberculosis in Ardabil province during 2011-16.

Materials and Methods
This retrospective descriptive cross-sectional study has been done on all 797 TB patients that registered in Ardabil province from 2011 to 2016. The sampling method was census and all TB registered cases during study years entered the study and all TB cases confirmed by experimental tests by specialists. All patients with positive smear results entered the study and doubtful cases without TB excluded from the study. Personal Information and epidemiological data such as age, Sex, residence place, name of city and clinical data (Smear results, type of TB, and cause of extra-pulmonary TB) were collected by a checklist for all registered TB patients and then analyzed through SPSS.16 software by descriptive and analytical statistical methods. Also, we used the population statistics of each study years for estimation the incidence of TB in Ardabil province during the study years. The data extracted from the national TB registered data of Ardabil province which ethically approved by Ardabil University of Medical Science, Ardabil, Iran.

Results
Of all patients, 429 (54%) cases were male and rest of them was female. The mean age of patients was 44.3±18.1 in ranging 1 to 91 years. 662 (83%) of patients were living in urban and 17% in rural areas. (Table 1) The most of Tb cases were seen in age group 35-65 years and the least of cases were in age group low than 10 years. The rate of incidence of TB during study years had swinging ( Table 2).
During study years, 452 cases (56.7%) had pulmonary TB that of them 52.2% occurred among men and 63.1% among urban people. There wasn't significant relation between TB type and sex but the relation between type of TB and residence place was significant (Table 3).
Of all cases, 0.6% had HIV, 56.7% had pulmonary TB and of them 77.2% had positive smear results (Table 4).
2.3% of patients had a prison history. The mean of overall TB incidence rate was 9.3 per hundred thousand in the city of Ardabil during the study years (Table 1).     Table 2). According to the results, the total rate of TB in year 2012 with 13.2 per 100000 was the most (Table 5).
Of all extra-pulmonary TB cases, the most of TB cases related to lymph nodes Tuberculosis with 84 cases (24.2%) ( Table 6). Results showed that the rate of smear positive and negative TB after 2012 had decreasing trend till end of study ( Figure 1).

Discussion
During study years, in Ardabil Province the mean of incidence rate was low than 11 per 100000 even though fluctuations have been observed over these six years. In Ebrahimzadeh et al., study the incidence rate of TB in Birjand had decreasing trend. Also, in Sofian study in Arak and Yazdani in Mazandaran there was decreasing trend. In Arsang study the total TB incidence rate had decreasing trend [8][9][10][11] The mean age of patients in this study was 44 which was in line with Beyramvand et al., study in south-east of Iran with 39 year and Vosougi et al., study in Hamadan with 54 year 2,12 .
In this study most of cases were in age group up 65 years. The most cases in Ilam and Arsang studies was up 65 years, in Hamadan up 50 year and in some places were in range 40-70 years 8,10-14 .
As the age of the immune system increases, as the age grows, the chance of becoming a tuberculosis infection increases with tuberculosis and also, we can consider the increasing age as a risk factor for TB suffering. In this study 39.5% of cases were in rural and 60.5% in urban areas which in other studies in Iran the urban rate changes from 51% to 64% which was in line with our study results [14][15][16] .
The results showed that of all cases, 56.7% had pulmonary TB and 43.3% had extra-pulmonary TB. Results showed that the type of TB in Ardabil province related  to the TB status in other places. The most of smear positive pulmonary TB cases is related to 2012 year, after 2012 year was declining that statistically no significant, it can be concluded that number of patients found have a constant trend. From all 797 patients, 43.8% in smear positive pulmonary TB, 12.9% in smear negative pulmonary TB and 61.7% in extra pulmonary TB cases were men that is similar to other studies 7,12 . Tb is the second leading cause of death from an infectious disease worldwide (after HIV which caused an estimated 1.8 million deaths in 2008). Tuberculosis is the largest cause of death from single factor infectious diseases in the world (more than Aids, Malaria and Measles). TB is in the tenth rank of burden diseases and predicted until 2020 maintain its current position and some time increase to seven ranks. Currently, the incidence of smear positive pulmonary TB is the main indicator to measure the situation of TB in the community is the number of people with smears positive pulmonary TB during a year per hundred thousand people. Doing screening tests for exposed people, applied new diagnosis and treatment methods must be included in TB control strategic programs. Also achieve to the smear positive case identification more than 85% and success in TB treatment rate more than 90% is predicted in country of Iran FOR 2025. Obviously, the lower mean age of patients reflects the situation of TB control is worse and upper mean age reflect it is better. In this study 39.5% of patients were in urban area which is similar with references resource. Primarily in areas with high population density and poor, TB prevalence expected to be high. Correct diagnosis of pulmonary tuberculosis is one of the problems in medicine and also as an important factor in TB epidemiology. In this study the frequency of patients in age group 35-65 years with 380(47.8%) is more than other age groups and based on the mean age of 44 years for patients can say that the pattern of disease in Ardabil city was slightly different from other places so, in other studies the disease is more in age up 60 years which this difference to became one of the challenges in the city of Ardabil 7,8,12,14 . In this study, pulmonary TB cases (56.7%) were more than extra-pulmonary cases and also, the most common organ involved in extra-pulmonary TB was lymph with 24.2% which is similar to other provinces patterns 7,8,14,15 . TB incidence rate in Iran has decreasing trend in recent ten years. The study on 134 countries in years 1997-2006 on TB incidence rate showed that the annually TB incidence decreasing rate is rapidly in high income countries 15 . According to statistics during the study years, the prevalence and incidence of TB in Iran has been decreased from 40 and 24 per 100000 in 2005 to 27 and 17 per 100000 in 2010; respectively. Also, TB incidence rate may be having significantly relation with welfare indicators such as income level, GDP and social conditions.

Conclusion
Due to the lack of decrease in the incidence of extra pulmonary tuberculosis in Ardabil province, we should have done more studies about this disease and effected causes for transmit, prediction and treatment of TB in Ardabil province. Also, by considering the affect of age on disease occurrence, it suggested that we most done exact screening in high risk age groups. Also, higher percentage of simultaneous HIV infections and tuberculosis in society and its effect on general health, so screening and early diagnosis of infections, training and doing necessary actions for prediction of people to suffering TB is recommended in future.

Conflict of Interest
None