Study design and setting
An institution based cross-sectional study was conducted. The study was conducted at Addis Ababa, the capital city of Ethiopia. According to the central statistical agency of Ethiopia, the city has an estimated total population of 3,103,999, out of which 1,479,000 were men and 1,624,999 women in 2012. In Addis Ababa there are ten sub-cities and 99 kebeles (the lowest administrative unit in Ethiopia). In the city there are 80 public health facilities, of which 14 are hospitals and the remaining 66 are health centers. Each health center has a catchment population of 40,000. There are also 35 private and 3 Non-Governmental Organizations (NGOs) hospitals in the city. The study was conducted from November 2013 to January 2014.
Source and study population
The source populations were TB patients who have follow up at public health facilities of Addis Ababa. Whereas the study populations were TB patients aged 18 years and above who have follow up at TB clinics of the selected public health facilities. TB patients who were 18 years and above, came to attend their follow up during the first two months of treatment and volunteers to participate were included in the study. All TB patients who cannot properly communicate, are mentally ill, have physical disabilities, and are pregnant or lactating mothers (Body Mass Index (BMI) was difficult to assess) were excluded from the study.
The outcome variable was undernutrition. Adult TB patients with BMI <18.5 Kg/m2 were considered to have undernutrition. BMI was calculated after measuring weight and height. In order to measure weight, the patient should remove shoes, in minimal clothing, standing erect on the center of the balance and record the weight to the nearest 0.1 kilo gram. By the same procedure the height was measured by asking the patient to be barefoot, wearing no head gear, knees were fully straight and both hands were held down to the side and record the height to the nearest 0.5 centimeter. The predictor variables were socio-demographic variables, eating problem, HIV status, dietary counselling, house hold hunger scale and participation in nutrition intervention.
Sample size determination
The sample size was determined considering the following assumptions using the single population formula. Z score at 95 % CI = 1.96, margin of error = 4 %, the prevalence of undernutrition among TB patients in Gondar 65.4 %  giving a sample size of 550. Since the numbers (470) of TB patient who have follow up at public health facilities in the study area were less than 10,000 we used correction formula which yields a sample size of 253. Then adding a 10 % non-response rate, the sample size became 278. A study conducted in Ghana  found income, educational status and family size to be factors associated with undernutrition among TB patients. By taking these factors into consideration, 95 % confidence interval, 10 % non-response rate, exposed to non-exposed ratio of 1:2 and taking 80 % power give the following results. Income (undernutrition among exposed 57 % and unexposed 43 % gives a sample size of 356), educational status (undernutrition among exposed 66 % and unexposed 44 % yields a sample size of 360) and family size (undernutrition in exposed 53 % and unexposed 47 % gives a sample size of 360). From the above calculation the minimum larger sample size was 360 which is the final sample size of this study.
In Addis Ababa there are ten sub-city health bureaus; from each sub-city one health center which renders anti-TB service was randomly selected based on the recent two months TB patient flow. Then the total sample size was proportionally allocated to the number of adult TB patients at each health center and participants were interviewed consecutively (Fig. 1). In order to avoid double counting those TB patients coming for follow up were asked if they were interviewed for this study in previous days and excluded from the interview if they had been.
Data collection tools, procedure and quality assurance
A pretested and structured questionnaire was used for the study (Additional file 1). After pretesting, some unclear or vague questions were modified and wrong skip patterns were also corrected. The questionnaire was prepared first in English and translated to Amharic (the official language of Ethiopia) then back to English so as to check for consistency. The data was collected by trained health professionals who have a previous basic knowledge of TB and those who are working in the TB clinic. Data collectors were provided with two days training on the objective, methods, tool and ethics of the study. The data collection process was supervised by two health officers and the principal investigator on a daily basis.
Data analysis and management
First, each questionnaire was cleaned and checked for completeness. Then the data were entered to EPI info version 3.6.1 computer software. Thereafter the data were exported to SPSS windows version 20 for analysis. Frequency, percentage and mean were run to get descriptive statistics of the data. Bivariate logistic regression analysis was done to explore the crude association between different predictor variables and undernutrition. To control for possible confounding factors and to identify factors that are independently associated with undernutrition, multivariate logistic regression analysis was performed for those variables with p value of less than 0.2 in the bivariate analysis. Having a p value less than 0.05 was used to declare the presence of statistically significant association between different variables.
Body mass index (BMI)
Is defined as the weight in kilogram of the individual divided by the square of the height in meter and used to determine the nutritional status of TB patients and classified as follows: Severe undernutrition (BMI < 16.0 Kg/m2), moderate undernutrition (BMI = 16.0-16.99 Kg/m2), mild undernutrition (BMI = 17.0-18.49 Kg/m2), normal weight (BMI = 18.5-24.99 Kg/m2), over weight (BMI = 25.0-29.99 Kg/m2) and obesity (BMI ≥30.0 Kg/m2) (Source: WHO 1995, 2000 & 2004).
Household Hunger Scale (HHS)
Is a household food deprivation scale derived from the United States (U.S) household food security survey module for use in developing country contexts and to assess the validity of the Household Food Insecurity Access Scale (HFIAS) for cross-cultural use. HHS has three house hold hunger categories as follows: HHS of 0-1 (little or no hunger), HHS of 2-3 (moderate hunger), HHS of 4-6 (severe hunger) in the house hold. (Source: Food and Nutrition Technical Assistance III Project (FANTA), 2011).
Is a process by which a health professional with special training in nutrition helps people make healthy food choices and form healthy eating habits.
✓ Working: Able to carry on normal activity and no special care needed.
✓ Ambulatory: Unable to work, able to live at home and able to care for most of personal needs and requires occasional assistance.
✓ Bed ridden: Unable to care for self, require institutional or hospital care
Nutritional care and support
Have many components such as nutrition education and counselling in health facilities, water, hygiene or food safety interventions to prevent diarrhea as well as provision of adequate quality/quantity of food and food aid by any organization.
The study protocol was reviewed and ethical clearance was obtained from Institutional Review Board of university of Gondar and Addis Ababa city administration health bureau. A formal letter of permission was sent to the respective health centers. The participant’s confidentiality was assured by avoiding their name and other personal identifying information. Participants were assured that their decision not to participate wouldn’t hamper their follow up care at the health facility and they can discontinue from participating in the research at any time. The interview took place after informed written consent was obtained from each participant.