Between July 2005 and December 2009, 362 patients with culture confirmed pulmonary tuberculosis were reported to Tarrant County Health and were eligible for study enrolment (Figure ). Of these, 320 (88%) were enrolled. Sixty-nine (22%) self-identified as non-Hispanic White, 85 (27%) as non-Hispanic Black, 81 (25%) as Asian, 82 (26%) as Hispanic and 3 (0.9%) were combined as "other" racial/ethnic group. The 3 subjects in the "other" racial/ethnic group were all male and included two with mild impairment and one non-impaired and were excluded from further analysis.
TB disease type and site, and patients' access to TB care was similar between race/ethnicity (Table ). There were significantly different demographic and clinical characteristics between race/ethnicity (Table ). HIV infection was significantly higher among non-Hispanic Blacks and level of education significantly lower among Hispanics compared to non-Hispanic Whites. Clinical and demographic characteristics, including age and smoking of US-born were significantly different from those who were foreign-born. Both proportion of ever-smokers and level of lifetime cigarette use was significantly higher among Whites (p < 0.001 for both measures) than other groups (Table ).
Demographic and clinical characteristics of 317 patients with pulmonary tuberculosis (TB) included in the analysis
The distribution of pulmonary impairment after tuberculosis (PIAT) and its severity among racial/ethnic groups, by smoking status and by socioeconomic status is shown in Figures , , and , respectively. PIAT was more frequent among non-Hispanic Whites compared to other race/ethnic groups (p < 0.001), and was more severe (p = 0.001) (Figure ). Pulmonary impairment was identified in 71% of non-Hispanic Whites, 58% of non-Hispanic Blacks, 49% of Asians and 32% of Hispanics. PIAT frequency was significantly higher among non-Hispanic Whites compared to other racial/ethnic groups in both ever-smokers and never-smokers, (p < 0.0001) (Figure ).
Figure 2 Comparisons of frequency and severity of pulmonary impairment between 317 self-identified racial and ethnic groups comprising 69 non-Hispanic Whites, 85 non-Hispanic Blacks, 82 Asians and 81 Hispanics. Figure 2 demonstrates that proportions impaired and (more ...)
Comparison of the frequency of pulmonary impairment among all self-identified racial groups by country of birth and smoking status.
Comparisons of the frequency and severity of pulmonary impairment among patient with different socioeconomic status. Figure 4 shows that proportions impaired and the severity of impairment does not vary with increase in socioeconomic status.
The distribution of employment, income, occupation, and education data among subjects was similar to that reported for other US TB patients (9-11). Education and income were significantly correlated (Pearson's correlation coefficient (r) = 0.21, p < 0.001). When occupational status was ranked according to prestige, it also significantly correlated with both education and income (r = 0.33, p < 0.001 and r = 0.15, p = 0.005, respectively). PIAT prevalence was evenly distributed across all levels of socioeconomic status: when the highest level of education attained was used as a proxy for socioeconomic status (Figure ).
The median "time to beginning TB treatment" for non-impaired persons was 62 days (interquartile range [IQR] was 12-110); 93 days for mildly impaired persons (IQR 61-110), 138 days for moderately impaired subjects (IQR 32-271), and 37 days for severely impaired subjects (IQR 12-60). There was no significant association between race/ethnicity and time to beginning TB treatment, (p = 0.978) (Table ). Similarly, no association between time to beginning treatment and PIAT was observed (p = 0.058) (data not shown).
We obtained baseline chest x-ray results for 99% of subjects (n = 314), and for 90% (n = 254) of subjects after either 20 weeks or at therapy completion. Pulmonary impairment was significantly (p < 0.001) correlated with the presence and magnitude of abnormal chest x-ray findings for both baseline (Spearman's correlation coefficient (r) = 0.4), and subsequent readings, (r = 0.42). Figure shows the distribution of a standardized severity index among subjects with pulmonary impairment identified by spirometry.
Distribution and severity of lung damage and baseline chest x-ray (first). Distribution and severity of lung damage at subsequent chest x-ray (second).
In univariate analysis race/ethnicity, age and US-birth were significantly associated with PIAT (Table ). The likelihood of PIAT increased by 2% (95% confidence interval [CI] 1, 3) for each 1 year increase in age. PIAT was 2.3 times more common (95% CI 1.46, 3.61) in US-born than foreign-born subjects. Race/ethnic groups and foreign birth were correlated: Spearman's r = 0.69, p < 0.001.
Unadjusted odds ratio for some pulmonary impairment
In a multivariate analysis that controlled for potential demographic and clinical confounders; the only significant predictor for PIAT was non-Hispanic White race/ethnicity, among whom PIAT prevalence was 3 times greater (95% C.I. 1.18, 8.40). Since race/ethnic group and foreign birth were significantly correlated, and to avoid confounding, separate multivariate regression models were constructed and are shown in Tables and . Risk factors for impairment were variable between race/ethnicity, with age independently predicting impairment in non-Hispanic Whites and non-Hispanic Blacks (Table ). Smoking was associated with three fold (95% CI 1.15, 7.85) increased risk for impairment among Asians, but was not predictive for impairment among non-Hispanic Whites (Table , Figure ). Table shows the multivariate regression model containing age, smoking and race/ethnicity of 144 US-born persons. In the model, only non-Hispanic White race/ethnicity and age independently predict PIAT. The age-related risk for PIAT increased 5% (95CI 2.0, 8.1) per year of age.
Predictors for pulmonary impairment in all 69 Whites, 85 Blacks, 82 Asians and 81 Hispanics with pulmonary tuberculosis
Predictors for pulmonary impairment in 144 US- born patients with pulmonary tuberculosis
Onset of age-related lung function decline is variable [19
]; however, for this study cohort onset of impairment was related to the age at which the different race/ethnic groups acquired tuberculosis. Consequently, the risk for moderate or severe pulmonary impairment is significantly higher among older Whites compared with non-Whites. As an example, the median age was 51 years for non-Hispanic Blacks, 59 for Whites, 56 for Asians and 71 years for Hispanics (Figure ). Similarly, the probability for developing moderate to severe impairment was higher in non-Hispanic Blacks of younger age groups compared to other race/ethnic groups (Figure , panel B). The median age for non-Hispanic Blacks was 63 and that for non-Hispanic Whites was 72, p
= 0.0239. The hazard ratio [HR] was 0.45 (0.22, 0.90).
Figure 6 Hazard ratios for different racial groups in developing some pulmonary impairment (Panel A.) and moderate or severe pulmonary impairment (Panel B) with increase in age. The median ages for panel A are; non-Hispanic Whites 58 years, non-Hispanic Blacks (more ...)