Study Area and Period
Hospital based unmatched case control study was conducted among 341 women attending gynecologic OPD in Nekemte town, from May 1 to July 30/2019. Nekemte town, the capital city of East Wollega zone, which is found at 331 km west of Addis Ababa. There are two public hospitals in the town namely Nekemte specialized hospital and Wollega University referral hospital. These hospitals give service to nearly 5 million people in western Ethiopia and adjacent areas. They have well organized gynecology and obstetrics departments which are led by 7 gynecologists.
All women attending gynecologic OPD at public hospitals in Nekemte town were the source population
All women attending gynecologic OPD at public hospitals in Nekemte town during the study period. Cases were women with utero-vaginal prolapse and controls were those women free from utero-vaginal prolapse but with some other gynecologic disease during the same study period. All women aged more than 18 years attending OPD during the study period were included into the study. However, critically ill women and women with mental problems were excluded from the study.
Sample Size Determination and sampling procedure
Sample size was calculated using Epi-info software version 7 using sample size determination for unmatched case–control studies. The parameters that were used to calculate sample size were; Confidence level 95%, power 80%, control to case ratio of 3: 1, the proportion of controls with exposure 6.2%, proportion of cases with exposure 18.5%, and Odd Ratio of 3.1. It was calculated from the study conducted in Bahir Dar town, North West Ethiopia by taking BMI (< 18.5 kg/m2) as one of the main exposure variables for pelvic organ prolapse that provide the maximum sample size . Therefore, it yields 78 cases and 232 controls. Adding a 10% non-response rate, the final sample size becomes 341 (86 cases and 258 controls).
Two hospitals in Nekemte town were selected purposively. Then based on the number of clients who visited gynecologic OPD of these two hospitals during previous three months, sample size was proportionally allocated to each hospital. For each case, three controls were selected consecutively.
Age, level of education, occupation, religion, ethnicity, marital status, educational status, income, obstetric factors, gynecologic history, medical factors
Data Collection Procedures
Data on socio demographic, obstetric, gynecologic and medical history were collected by using a pre-tested structured questionnaire which was developed by reviewing different literatures [13, 27, 30, 32]. Cases were identified by trained physicians working at gynecology OPD of the hospitals. Four nurse professionals were recruited and trained to collect data. All questionnaires were checked for completeness by the principal investigator.
Physical measurement was used to obtain data on weight and height of women. In this regard, the weight of each woman was measured using balanced beam in kg nearest to 0.1kg and height was measured using measuring tape to the nearest 0.1cm.
Shaw’s classification system of utero vaginal prolapse was used for grading of the disease. In this classification system, descent is classified into four grades; the first grade is descent of cervix into the vagina, second grade is descent of cervix into introitus, third grade is descent of the cervix outside introitus, and the fourth grade is when the whole of the uterus is outside introitus .
Data Quality Assurance
The questionnaire was first prepared in English and then translated to local language (Afan Oromo). The data collectors and supervisors were trained for two days on data collection and details of the study. Pretest was conducted on 4 cases and 12 controls at Mettu Karl Hospital which is located in south west Ethiopia.
Data Processing and Analysis
Data entry was done using Epi-Info version 3.5.3 after checking for completeness. It was then cleaned and exported to SPSS Version 20 for analysis. Frequencies and other descriptive statistics were done. Bivariate analysis was used to examine the association between dependent and independent variables; Odds Ratios (ORs) and their 95% Confidence Intervals (CIs) were calculated. All variables that had a P-value of < 0.2 in the bivariate analysis were included in the multivariate logistic regression analysis model to determine the factors associated with dependent variables. Statistical significance was set at p-value of < 0.05.