An Analysis of the Survival Probability of Tuberculosis Patients with Right Censored and Interval Censored Observation in Zahedan during 2014 - 2016

This study was conducted on patients with tuberculosis (TB), based on regional needs and the outbreaks of the contagious disease, particularly those diagnosed with the smear-positive during 2014 - 2016. The regions neighboring this province, low health information, poorly equipped hospitals/medical clinics, high rate of welfare, the illegal entrance of foreigners to the province are necessities that have to be mentioned. Spreading awareness of the disease in the province and the examination of possible ways to control and prevent its spreading are the purposes of this study. First, the information concerning the files of 250 patients with smear-positive pulmonary tuberculosis was collected in Zahedan’s Tuberculosis Coordinator and the diagnostic criterion for the studied participants was a microscopic observation of the sputum. All patients had a chest X-ray and were examined every two months by an infectious disease specialist who diagnosed them with smear-positive pulmonary tuberculosis. As the observations were incomplete, we could not apply the regular methods and SPSS software to estimate the survival probability (function); instead, we used Generalized Turnbull’s Estimator (GTE) and R software to calculate the non-parametric conditional probability of the patient’s survival and recovery times. For Instance, for the ith person, Li and Ri have been considered based on the last positive result and the first negative result of the disease, respectively. Among 250 studied patients, four patients are right censored and the rest of them are interval censored. The patients’ age ranged from 10 to 91 years, the average age of diagnosis in infected males is 58.54 with a standard deviation (SD) of 19.10 years and females was 55.40 with an SD of 18.09 years. During this period there were no major differences between males and females. Moreover, 49.2% of the patients infected via sexual transmission were males and 50.8% of the patients were females. In this study, the patients’ weight was considered an effective variable in the evaluation of the survival function (the possibility of conditional survival) and we considered the effect of factors such as sex, the previous diagnosis of diabetes/AIDS, the previous history of being in contact with people with TB disease, and a history of imprisonment on the survival probability. As we can see, all the auxiliary variables mentioned above, are significantly effective in the course of the patient’s treatment and recovery (survival) time.