Tuberculosis: A Risk Factor Approach

Background Multiple studies of tuberculosis treatment have indicated that patients with diabetes mellitus may experience poor outcomes. We performed a systematic review and meta-analysis to quantitatively summarize evidence for the impact of diabetes on tuberculosis outcomes. Methods We searched PubMed, EMBASE and the World Health Organization Regional Indexes from 1 January 1980 to 31 December 2010 and references of relevant articles for reports of observational studies that included people with diabetes treated for tuberculosis. We reviewed the full text of 742 papers and included 33 studies of which 9 reported culture conversion at two to three months, 12 reported the combined outcome of failure and death, 23 reported death, 4 reported death adjusted for age and other potential confounding factors, 5 reported relapse, and 4 reported drug resistant recurrent tuberculosis. Results Diabetes is associated with an increased risk of failure and death during tuberculosis treatment. Patients with diabetes have a risk ratio (RR) for the combined outcome of failure and death of 1.69 (95% CI, 1.36 to 2.12). The RR of death during tuberculosis treatment among the 23 unadjusted studies is 1.89 (95% CI, 1.52 to 2.36), and this increased to an effect estimate of 4.95 (95% CI, 2.69 to 9.10) among the 4 studies that adjusted for age and other potential confounding factors. Diabetes is also associated with an increased risk of relapse (RR, 3.89; 95% CI, 2.43 to 6.23). We did not find evidence for an increased risk of tuberculosis recurrence with drug resistant strains among people with diabetes. The studies assessing sputum culture conversion after two to three months of tuberculosis therapy were heterogeneous with relative risks that ranged from 0.79 to 3.25. Conclusions Diabetes increases the risk of failure and death combined, death, and relapse among patients with tuberculosis. This study highlights a need for increased attention to treatment of tuberculosis in people with diabetes, which may include testing for suspected diabetes, improved glucose control, and increased clinical and therapeutic monitoring.

There are 9 million cases of active tuberculosis reported annually; however, an estimated one-third of the world's population is infected with Mycobacterium tuberculosis and remains asymptomatic. Of these latent individuals, only 5-10% will develop active tuberculosis disease in their lifetime. CD4(+) T cells, as well as the cytokines IL-12, IFN-γ, and TNF, are critical in the control of Mycobacterium tuberculosis infection, but the host factors that determine why some individuals are protected from infection while others go on to develop disease are unclear. Genetic factors of the host and of the pathogen itself may be associated with an increased risk of patients developing active tuberculosis. This review aims to summarize what we know about the immune response in tuberculosis, in human disease, and in a range of experimental models, all of which are essential to advancing our mechanistic knowledge base of the host-pathogen interactions that influence disease outcome.

This study evaluates polymorphonuclear neutrophil (PMN) cell performance in 61 diabetic patients free of infection (40 Type 1, 21 Type 2), using tests that explore all the functional steps of PMN: (1) adherence: expression of adhesion molecules, CD 11a, CD 11b, CD 11c; nylon fiber adherence test; (2) chemotaxis under agarose towards the bacterial oligopeptide FMLP and complement fractions, used as attracting agents; (3) phagocytosis of opsonized latex microbeads; (4) bactericidal activity: chemiluminescence assessment of the oxidative killing potential before and after stimulation by opsonized zymosan and PMA; nitroblue tetrazolium reduction test. Results were analysed according to potentially influential factors: metabolic control (HbA1C, glycaemia), age of patient, type of diabetes, disease duration, and existence of vascular complications. PMN chemotaxis was significantly lower in patients than in healthy controls (p < 0.001) and associated with spontaneous adherence and increased expression of adhesion molecules (CD 11b, CD 11c). The increased response to chemiluminescence reflects spontaneous activation of PMN cells and increased free radical production; after stimulation, response was lower than in controls. The type of diabetes, the age of patients, HbA1C level and disease duration did not affect the responses. Chemotaxis and chemiluminescence were further reduced in patients with vascular complications and hyperglycaemia. We conclude that all steps of PMN functioning are altered in diabetic patients, which may increase the risk of vascular complications and infectious episodes.