Survival analysis of adult tuberculosis disease

We conducted a survival analysis of all the confirmed cases of Adult Tuberculosis (TB) patients treated in Cork-City, Ireland. The aim of this study was to estimate Survival time (ST), including median time of survival and to assess the association and impact of covariates (TB risk factors) to event status and ST. The outcome of the survival analysis is reported in this paper.

We used a retrospective cohort study research design to review data of 647 bacteriologically confirmed TB patients from the medical record of two teaching hospitals. Mean age 49 years (Range 18-112). We collected information on potential risk factors of all confirmed cases of TB treated between 2008-2012. For the survival analysis, the outcome of interest was 'treatment failure' or 'death' (whichever came first). A univariate descriptive statistics analysis was conducted using a non- parametric procedure, Kaplan -Meier (KM) method to estimate overall survival (OS), while the Cox proportional hazard model was used for the multivariate analysis to determine possible association of predictor variables and to obtain adjusted hazard ratio. P value was set at <0.05, log likelihood ratio test at >0.10. Data were analysed using SPSS version 15.0.

There was no significant difference in the survival curves of male and female patients. (Log rank statistic  = 0.194, df  = 1, p = 0.66) and among different age group (Log rank statistic  = 1.337, df = 3, p = 0.72). The mean overall survival (OS) was 209 days (95%CI: 92-346) while the median was 51 days (95% CI: 35.7-66). The mean ST for women was 385 days (95%CI: 76.6-694) and for men was 69 days (95%CI: 48.8-88.5). Multivariate Cox regression showed that patient who had history of drug misuse had 2.2 times hazard than those who do not have drug misuse. Smokers and alcohol drinkers had hazard of 1.8 while patients born in country of high endemicity (BICHE) had hazard of 6.3 and HIV co-infection hazard was 1.2.

There was no significant difference in survival curves of male and female and among age group. Women had a higher ST compared to men. But men had a higher hazard rate compared to women. Anti-TNF, immunosuppressive medication and diabetes were found to be associated with longer ST, while alcohol, smoking, RICHE, BICHE was associated with shorter ST.