ANNUAL RISK OF TUBERCULOUS INFECTION (ARI) IN

NORTH ZONE OF INDIA

(Submitted for publication to bulletin of WORLD HEALTH ORGANISATION)

ABSTRACT

 

Objective: To estimate Annual Risk of Tuberculous Infection (ARI) in North zone of India.
Methods: A community based cross-sectional tuberculin survey was conducted among children aged 1 to 9 years residing in a sample of villages and urban blocks of six selected districts in North zone of India. A stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 48,323 children in 598 clusters were subjected to tuberculin testing with 1TU PPDRT23 with Tween 80 and maximum transverse diameter of induration was measured about 72 hours after the test.
Findings: Among the test read children, 45.3% were found to be with BCG scar. The frequency distribution of tuberculin reaction size among 25,816 children without BCG scar was bimodal. All reactions ³ 14 mm were considered attributable to infection with tubercle bacilli, for estimating prevalence of infection. The prevalence of infection with tubercle bacilli among children without BCG scar was estimated to be 10.3%. The ARI was computed as 1.9%. The proportion of infected children was found to be significantly higher in urban compared to rural areas.
Conclusion: The high rate of ARI in the north zone of India calls for further intensification of tuberculosis control efforts.
Keywords: Tuberculin test, Cross-sectional survey, cluster sampling, Children without BCG scar, Prevalence, Infection with tubercle bacilli, Annual risk of infection.

 

ANNUAL RISK OF TUBERCULOUS INFECTION IN

THREE DISTRICTS OF MAHARASHTRA

V K Chadha, et al

 

ABSRACT

A nation wide tuberculin survey to estimate the annual risk of infection (ARI) in different parts of India is currently under progress. For this purpose, three districts viz. Nagpur, Thane and Ratnagiri were selected from the state of Maharashtra. A total of 29,805 children aged 1 to 9 years from the rural and urban areas of these districts were subjected to tuberculin testing with ‘1TU PPDRT23 with Tween 80’ and maximum transverse diameter of induration was measured about 72 hours later. The cut-off point for identification of ‘infection with tubercle bacilli’ was identified at 15 mm, based on the frequency distribution of reaction sizes among children without BCG scar.

The estimated ARI in the rural and urban areas of Nagpur district was 1.2% and 1.6% respectively. It was 1.6% and 3.3% in the rural and urban areas of Thane district. In rural areas of Ratnagiri district, the ARI was estimated as 1.8%.

The results indicate a high rate of transmission of tuberculous infection in the community and suggest further intensification of tuberculosis control measures, especially in the urban areas.

 

 

 

 

ANNUAL RISK OF TUBERCULOUS INFECTION IN RURAL AREAS OF UTTAR PRADESH, INDIA

(Submitted for publication to INTERNATIONAL JOURNAL of TUBERCULOSIS and LUNG DISEASES)

 

SUMMARY

 

Setting: Rural areas of three districts of Uttar Pradesh, the most populous state in India.
Objectives: To estimate Annual Risk of Tuberculosis Infection (ARI).
Study Design: A cross-sectional tuberculin survey was conducted among children aged 1 to 9 years residing in the selected samples of villages in three districts of Uttar Pradesh viz. Rae Bareli, Hardoi and Jaunpur. The registered children were subjected to tuberculin testing with 1TU PPDRT23 with Tween 80 and maximum transverse diameter of induration was measured about 72 hours after the test. ARI was estimated based on the antimode identified on the frequency distribution of reaction sizes among children without BCG scar.
Results: The proportion of children with BCG scar varied from 25% to 31% in the three districts. A total of 4837 children without BCG scar were test-read in Rae Bareli, 6152 in Hardoi and 7253 in Jaunpur district. The cut-off point for identification of infection with tubercle bacilli was observed at 14 mm in Rae Bareli district and 13 mm in Hardoi and Jaunpur districts. The prevalence of tuberculosis infection among children aged 1 to 9 years in the rural areas of three districts was estimated as 11.80%, 11.02% and 8.85% respectively with the computed ARI rates being 2.11%, 2.03 % and 1.61%.
Conclusion: High rates of transmission of tuberculous infection in rural areas of the state of Uttar Pradesh call for urgent and intensified Implementation of tuberculosis control measures.

 

 

ANNUAL RISK OF TUBERCULOUS INFECTION IN WEST ZONE OF INDIA

(Submitted for publication in INTERNATIONAL JOURNAL of EPIDEMIOLOGY)

SUMMARY

 

Background: Tuberculosis continues to be a major public health problem in India. However, there is a paucity of information on the prevailing epidemiological situation of tuberculosis (TB) for most parts of India. Hence it was decided to carry out a nation wide tuberculin survey to estimate Annual Risk of Tuberculous Infection (ARI) in different part of India. The results from west zone of India are presented.
Methods: A community based, cross-sectional tuberculin survey was conducted among children aged 1 to 9 years residing in a sample of rural and urban areas of six districts in west zone of India. A stratified two-stage cluster sampling was adopted for selection of rural and urban clusters. A total of 48 473 children in 600 clusters were subjected to tuberculin testing with 1TU PPDRT23 with Tween 80 and maximum transverse diameter of induration was measured about 72 hours after the test.
Findings:

The BCG scar was observed in 52% of the test read children. Based on the frequency distribution of tuberculin reaction size among 22 259 children without BCG scar, the reactions ³ 15 mm were considered attributable to infection with tubercle bacilli, for estimating prevalence of infection. The prevalence of infection was estimated to be 9.3%. The ARI computed from the estimated prevalence was 1.8%. The proportion of infected children was found to be significantly higher in urban than in rural areas.

Conclusion: The high rate of ARI in the west zone of India calls for further intensification of tuberculosis control efforts.
Keywords: Tuberculin test, Cross-sectional survey, Cluster sampling, Children without BCG scar, Prevalence, Infection with tubercle bacilli, Annual risk of infection, India.

 

PPD RT23 FOR TUBERCULIN SURVEYS IN INDIA

(Submitted to INTERNATIONAL JOURNAL of TUBERCULOSIS and LUNG DISEASES)

SUMMARY
Setting:

Tuberculosis Sanatoria and villages of Bangalore district.

Objectives: To study the appropriateness of continued use of 1TU dilutions prepared in India from freeze dried form of PPD RT23 with Tween 80 received from SSI, Copenhegen, for tuberculin surveys in India.
Design: The responses to dual tuberculin tests were compared among:
  1. 63 smear positive cases using 2TU PPD RT23 dilutions prepared by BCG Laboratory, Guindy (Dilution-G) and 2TU PPD RT23 Dilutions prepared by SSI (Dilution-S).
  2. 124 smear positive cases using 1TU and 2TU of Dilution–G.
  3. 1338 apparently healthy children using 1TU and 2TU of dilution-G.

Allocations of test sites were made using double-blind randomized technique. Further, tuberculin responses obtained during various studies conducted within India and other countries were compared.

Results : The differences in sensitivity of tuberculin test using different preparations viz. 2TU of Dilution-S and 1TU and 2TU of Dilution-G were found to be small and statistically non-significant. Among children, a higher proportion of reaction sizes in 10-14 mm and 15+ mm categories was observed to 2TU compared to 1TU of Dilution-G. This could be reflective of lower specificity of 2TU in the study area where non-specific sensitivity is highly prevalent. Various studies in India and other countries do not suggest any loss in potency of 1TU PPD RT23 with tween 80.
Conclusion: Use of 1TU dilutions of PPDRT23 with Tween 80 obtained from BCG Lab, Guindy may be continued for tuberculin surveys in India.

 

Annual Risk of Tuberculous Infection in

rural areas of Junagadh District

 

ABSTRACT:

Paucity of epidemiological data on tuberculosis in India prompted the National Tuberculosis Institute, Bangalore to embark upon a Nation-wide survey to estimate the Annual Risk of Tuberculosis Infection in different parts of the country. The survey in Junagadh district, one of the 26 districts drafted under the nation-wide survey is reported here.

The prevalence of infection from the analysis of 3164 children not displaying scars of the BCG vaccination was 4.16 % (C.I : 3.17-5.14) and from this data the ARI was computed as 0.73%(C.I: 0.55-0.91). The inclusion of vaccinated children into the study group yielded similar results.

The estimate of the ARI in Junagadh district is lesser than that in several other parts of India which is probably in consonance with its better socio-economic development.

 

 

PPD RT23 FOR TUBERCULIN SURVEYS IN INDIA 

V.K Chadha, P.S Jagannatha, Preetish Vaidyanathan, P. Jagota 

(Submitted for publication in The International Journal of Tuberculosis and Lung Disease)

  

Setting:          Tuberculosis Sanatoria and villages of Bangalore district. 

Objectives:   To study the appropriateness of continued use of 1TU dilutions prepared in India from freeze dried form of PPD RT23 with Tween 80 received from SSI, Copenhegen, for tuberculin surveys in India.  

Design:        The responses to dual tuberculin tests were compared among:

(i)                 63 smear positive cases using 2TU PPD RT23 dilutions prepared by BCG Laboratory, Guindy (Dilution-G) and 2TU PPD RT23 Dilutions prepared by SSI (Dilution-S).

(ii)               124 smear positive cases using 1TU and 2TU of Dilution–G.

(iii)              1338 apparently healthy children using 1TU and 2TU of dilution-G.  

Allocations of test sites were made using double-blind randomized technique.   

Further, tuberculin responses obtained during various studies conducted within India and other countries were compared.  

Results :      The differences in sensitivity of tuberculin test using different preparations viz. 2TU of Dilution-S and 1TU and 2TU of Dilution-G were found to be small and statistically non-significant. Among children, a higher proportion of reaction sizes in 10-14 mm and 15+ mm categories was observed to 2TU compared to 1TU of Dilution-G. This could be reflective of lower specificity of 2TU in the study area where non-specific sensitivity is highly prevalent. Various studies in India and other countries do not suggest any loss in potency of 1TU PPD RT23 with tween 80.  

Conclusion:   Use of 1TU dilutions of PPDRT23 with Tween 80 obtained from BCG Lab, Guindy may be
  
                     continued for tuberculin surveys in India .