Daniel M. Keller, PhD

July 16, 2012

July 16, 2012 (Bangkok, Thailand) — China has cut the prevalence of tuberculosis (TB) in half and the number of deaths from TB by 75% over the past 2 decades. Despite these gains, China is still ranked second in the world for TB disease burden.

Weibing Wang, PhD, associate professor of epidemiology at the School of Public Health at Fudan University in Shanghai, China, reported these results here at the 15th International Congress on Infectious Diseases. His team conducted a retrospective cohort study to investigate the factors associated with all-cause and TB-specific deaths among TB patients in 4 urban settings in China.

Dr. Wang said that from 1990 to 2010, the prevalence of TB decreased from slightly more than 200 per 100,000 population to slightly more than 100 per 100,000 population. At the same time, mortality (excluding HIV coinfected patients) decreased from about 18 per 100,000 population to about 4 per 100,000 population.

In patients without HIV, deaths from TB decreased from 24% in 1990 to 6% in 2009. Although TB treatment in China is provided free of charge, the epidemic is unbalanced, with a higher prevalence of the disease in the cities than in rural areas, Dr. Wang explained.

Appropriate antibiotic use can prevent death in most patients with TB. However, many of the factors associated with TB death have never been clearly established, he noted.

In their study, Dr. Wang and colleagues collected data in 4 of the 19 districts in Shanghai from a national TB information system, medical records, a case-management system, face-to-face or telephone follow-up interviews, and death records. The 4 districts comprised about 6 to 7 million of the 20 million residents of Shanghai.

The study involved patients with pulmonary TB from January 1, 2004 to December 31, 2008. Patients with extrapulmonary TB were excluded. Of 5001 patients who qualified for inclusion, 4271 were eligible for analysis.

Two to 6 years after diagnosis, 15% of the patients had died from any cause, and 17% had died from TB. In other words, TB was the cause of death in 2.5% of all the patients, and resulted in 7.2 years of life lost per patient. Dr. Wang explained that this 17% rate is "very similar to that in developed countries, like the United States and Canada."

The rates for both all-cause and TB-specific deaths were highest in the first year after diagnosis. "From the second year of treatment, the risk of death was dramatically lower, compared with the first year," Dr. Wang said.

Being male was significantly associated with all-cause (P < .001) and TB-specific (P = .001) death. After adjustment for age, sex, and treatment history, 4 factors were significantly associated with a higher risk for all-cause death (P < .05 for all) — psychopathology (hazard ratio [HR], 2.09; 95% confidence interval [CI], 1.04 to 4.20), chronic bronchitis (HR, 1.47; 95% CI, 1.05 to 2.04), cancer (HR, 1.72; 95% CI, 1.10 to 2.68), and having 2 or more diseases (HR 1.42; 95% CI, 1.04 to 1.94). The only significant factor for TB-caused death was chronic bronchitis, and that was only when the HR was not adjusted for other factors (unadjusted HR, 3.77; 95% CI, 1.76 to 8.09; P < .01).

Other respiratory ailments accounted for about 36% of deaths, cancers for nearly 20%, circulatory problems for 10%, and other or unknown causes for 17%.

Dr. Wang concluded that the multiple factors that lead to death in TB patients must be considered when control measures are being developed. He suggested that running TB control programs alongside other public health programs might be necessary to better address the health of these patients and reduce mortality. "And attention to the first year during TB treatment is very important," he noted.

Session moderator Narin Hiransuthikul, MD, MPH, PhD, chair of the Department of Social and Preventive Medicine at Chulalongkorn University in Bangkok, Thailand, who was not involved in the study, told Medscape Medical News that one limitation of the study is that it is not possible to tell why the death rate was higher in first year of treatment from the data presented.

"It may be due to the tuberculosis by itself, or it may be due to some kind of treatment that you give to the patient," he said.

In addition, the cause of death might not have been exact in all cases. "The big problem is how to verify that a death was due to the TB, and not another cause." Sometimes patients have both TB and other conditions, Dr. Hiransuthikul noted. He said all these uncertainties need to be taken into account when interpreting the study results.

But he noted that a strength of the study is that it was done in China, where "you have a large sample...and you can follow-up for a long time."

Dr. Hiransuthikul has disclosed no relevant financial relationships.

15th International Congress on Infectious Diseases (ICID): Abstract 14.005. Presented June 14, 2012.