Relationship of ARTI to incidence and prevalence of tuberculosis in a district of south India.

OBJECTIVE: To validate the currently used empirical relationship between annual risk of tuberculous infection (ARTI) and incidence and prevalence of smear-positive cases. SETTING: Two disease surveys to estimate the prevalence and incidence of tuberculosis (TB) among adults in Tiruvallur district, south India, and a tuberculin survey to estimate the ARTI among children. RESULTS: The incidence of TB was estimated to be 82 and prevalence 210 per 100,000 population and ARTI 1.6%. We estimated that 1% ARTI corresponded to 51 new and 131 prevalent cases. CONCLUSION: The currently used empirical relationship between ARTI and incidence can be used by programme managers as an effective monitoring tool.

Trends in the prevalence and incidence of tuberculosis in south India.

OBJECTIVE: To study trends in the prevalence and incidence of tuberculosis in south India. METHODS: In 1968-1970, about 100,000 subjects were surveyed for tuberculosis and followed thereafter for 15 years, mainly by repeat survey once every 2.5 years. New entrants were inducted at every repeat survey. Radiographic examination of subjects aged 5 years or more and sputum smear and culture examinations of those with an abnormal shadow were undertaken; tuberculin tests were done initially on all, and at 4, 10 and 15 years in selected samples of those aged 1-9 years. RESULTS: The prevalence of culture-positive tuberculosis decreased by 1.4% per annum to 694/100,000, while that of smear-positive tuberculosis showed no significant decrease from 457/100,000. The annual incidence of culture-positive tuberculosis decreased by 4.3%/annum to 189/100,000 and that of smear-positive tuberculosis decreased by 2.3%/annum to 113/100,000. Decreases in incidence occurred exclusively in those with abnormal radiographic findings suggestive of tuberculosis at the start of the period. The annual risk of tuberculosis infection (ARTI) was initially 2%, and showed no sign of decline over the period. CONCLUSION: The prevalence of tuberculosis and ARTI showed little or no decrease over the 15-year period. A significant decrease in incidence occurred, but exclusively in those with abnormal radiograph suggestive of tuberculosis at the start of the period.

Serial evaluation of serum neopterin in HIV seronegative patients treated for tuberculosis.

OBJECTIVE: To delineate the course of serum neopterin (s-neo) concentrations in patients with pulmonary tuberculosis who are on anti-tuberculosis therapy. DESIGN: S-neo concentrations were measured by high performance liquid chromatography (HPLC) in 39 patients treated for pulmonary tuberculosis at pretreatment, at one month and at end of treatment. It was also measured in 11 relapse cases and their matched controls at the above time points and at the time of relapse. The results were correlated with bacteriological and radiological findings. RESULTS: All patients had elevated levels of s-neo at pretreatment which had declined at 1 month and were near normal at the end of treatment. The decline was more significant in patients with moderate lesions, suggesting that immune activation is maximum in this group of patients. The mean decrease was 37% at one month and 66% at the end of treatment. The corresponding decreases were 11% and 56% in patients with limited lesions and 11% and 45% in those with extensive lesions. It continued to fall after completion of therapy in patients who did not relapse, whereas an increase after completion of therapy was associated with bacteriologically proven relapse. CONCLUSIONS: The measurement of s-neo concentration could be of help in evaluating response to therapy. This study provides a rational basis for the association between s-neo concentration and relapse.

Associations of HLA-DRB1, DQB1 and DPB1 alleles with pulmonary tuberculosis in south India.

SETTING: Tuberculosis is endemic in south India: sputum positive pulmonary tuberculosis is predisposed by HLA-DR2 in south India and few other populations of the world. OBJECTIVE: To study HLA-DRB1, DQB1, DQA1 and DPB1 allelic polymorphism in pulmonary tuberculosis patients and endemic controls from south India. DESIGN: One hundred and twenty-six, sputum positive pulmonary tuberculosis patients and 87, endemic controls, from Madurai were studied for MHC class II allelic polymorphism by PCR-SSOP method. XI IHWC primers and probes and non-radioactive probing methods were employed. RESULTS: HLA DRB1*1501 and DQB1*0601 predisposed for pulmonary tuberculosis (DRB1*1501: odds ratio (OR) = 2.68, 95% confidence interval (CI) = 1.30-5.89, P value (P) = 0.013, aetiological fraction (EF) = 0.17; DQB1*0601: OR = 2.32, CI = 1.29-4.27, P = 0.008, EF = 0.26). Haplotype DRB1*1501-DQB1*0601 was higher in patients (1324 per 10,000, X2 = 27.07) than controls (F = 404/10,000, X2 = 8.84). In a subset of 63 caste matched samples, DPB1*04 was preventive (OR = 0.45, CI = 0.21-0.95, P = 0.036, PF = 0.26): the distributions of DRB1*1501-DQB1*0601-DPB1*04 phenotypes were different between patients and controls (P = 0.0092). These alleles were predominant in patients and controls of T5SU caste. CONCLUSION: HLA-DRB1*1501 and DQB1*0601 predisposed to sputum positive pulmonary tuberculosis, and DPB1*04 was preventive and epistatic to this risk. Caste T5SU is an ideal model to study immunology of tuberculosis.