Co-morbidity of Diabetes and Tuberculosis Can Affect the Results of Treatment; A Case Control Study in Iran

Background and Purpose: Several evidences have shown some synergistic effect of diabetes co-morbidity on the tuberculosis (TB) treatment results, while some other studies have not found such associations. This study aimed to investigate the relationship between TB-diabetes co-morbidity and outcomes of TB treatment. Materials and Methods: The research population in this case control study were patients with smear positive tuberculosis. The cases were 158 patients with TB and diabetes selected by consensus method, while controls were 316 patients randomly selected from TB patients without diabetes. Results: Frequency of unfavorable outcome among cases was higher than among controls (7.6% vs 7.3% respectively, p-value =0.901). Multivariate logistic regression models showed that the odds ratios for adverse treatment outcome, death, treatment failure, positive smear after the intensive phase of treatment and high grade positivity (2+ & 3+) were 0.97(0.45- 2.06), 0.97(0.42-2.24), 0.91(0.17-4.85), 1.39(0.79- 2.44) and 2.57(0.83- 7.92) respectively. Moreover, treatment adverse outcomes among patients with drug complications (22.2% vs. 6.5%, p-value =0.010) and rural residents (10% vs 4.9% respectively, p-value =0.037) were significantly higher than those among patients without complication and urban residents respectively. Conclusion: Although we did not observe any significant association between TB-diabetes co-morbidity and treatment results, there was a significant effect measure regarding the effect of smear positivity at the end of the intensive phase of treatment, especially high grade of smear positivity. Because of probable bias in the classification of the exposure, screening of TB patients regarding diabetes mellitus at the beginning of the treatment is recommended.