Indian Pediatrics 2003; 40:239-243 

Prevalence of Tuberculosis Infection Among Children in Slums of Ahmedabad

Key words: Prevalence, Slums,Tuberculosis.

Prevalence of tuberculosis infection obtained through tuberculin testing in children, over a period of time, is recognized to be a reliable indicator for evaluating the tuberculosis situation and its trend in the community(1). Annual rate of infection (ARI) expresses the overall impact of various factors influencing the transmission of tubercle bacilli. It holds the key to the study of epidemiological trends since any change in disease situation and programme imple-mentation efficiency is first reflected in change in ARI values(2).

Tuberculosis is commonly associated with poverty, overcrowding, illiteracy and mal-nutrition. Living conditions in cities have deteriorated in recent years due to unprecedented migration and population growth. The upward shift in age structure and advent of HIV epidemic are likely to further aggravate the situation. Tuberculosis is also described as urban health penalty. Thus it is required to evaluate the TB situation from time to time. A tuberculin survey (a preliminary study) was conducted in urban slums of Ahmedabad city to estimate the prevalence of infection in order to assess the existing situation of tuberculosis.

Subjects and Methods

Ahmedabad city has five zones and 43 election wards. In these 43 wards, 90,119 houses are situated in 2432 slum pockets. Listing of all 43 wards with total households of each area was done. A cumulative frequency of the household was found out after arranging them in a list and 30 clusters selected from this by cluster sampling method(3).

Children below 15 years of age without BCG scar were chosen for the tuberculin testing. For sampling UIP evaluation survey method was used. By house-to-house survey method 7 eligible children were identified from each cluster completing total 210 children in selected 30 clusters. Consent was taken from the parents before subjecting them for tuberculin testing. Identified children were tested by 1TU PPD RT 23 with Tween 80. A dose of 0.1 ml was injected intradermally on the flexor surface of forearm. Maximum transverse diameter of the site was measured on the third day (after 72 hours). The administration of tuberculin injection and its reading were done by highly experienced health workers of the District Tuberculosis Demonstration Center, Ahmedabad.

To estimate the prevalence of infection, the standard cut-off values of 10 mm is taken as level of demarcation between infected and uninfected children. The proportion of children above the level of demarcation was obtained as estimated prevalence of infection.

The average ARI calculated by the formula(4)

ARI = 1 – (1 – P)1/A

where P = Prevalence of infection,

A = Median age of children surveyed.

Results

Of 210 children, 118 (56.2%) were boys and 92 (43.8%) girls; 70% of the children were above the age of five years (Table I) and median age was 6.3 years. The degree of induration did not show gender differences (P >0.05)

Table I__Prevalence of Tuberculosis Infection in Different Age Groups

Age group (yr)	N	Infected children	Prevalence rate (%)	95% CI
0- 4	63	5	7.9	1.1-14.7
5- 9	94	36	38.3	28.3-48.3
10-14	53	23	43.4	29.8-57.0
0-14	210	64	30.4	24.0-36.7

95% CI : 95% confidence intervals

 

The frequency distribution of tuberculin reaction sizes for children without BCG scar for overall study group is presented in Fig.1. A bimodal distribution was observed with first mode at 0-4 mm and second mode at 5-30 mm. Since there was no clear-cut demarcation between infected and noninfected in the second mode, a standard cut off induration of 10 mm size was considered to demarcate infected from non-infected children. The prevalence rate of tuberculosis infection in children was found to be 30.4% (95% CI 24.0-36.7), as 64 children out of 210 had induration >10 mm size. The prevalence rate of tuberculosis infection in different age group is presented in Table I. The highest prevalence was observed in the age group of 10-14 years (43.4%, 95% C.I. 29.8 - 57.0). The estimated average annual risk of infection was found to be 5.4% in the age group of 0-14 years.

Size of Induration (in mm)

 

Fig. 1. Distribution of children according to size of induration.

Discussion

Tuberculosis infection in the community is the result of the interplay between the socio-economic status of the population, the host and the agent characteristics. A high prevalence of tuberculosis infection was observed in the present study (20.5%) with ARI 5.4%. A high rate of ARI (3%) was also observed in the study conducted among urban slum children of Chooli in Chennai(5). Another study conducted among school children in Bangalore city observed 11.0% prevalence of infection with ARI 1.7%(2). In various studies the prevalence rate of infection ranged from 4-12% (Table II). It appears that considerable differences exist in the infection rate among children from area to area within the country. This could be a manifestation of the prevailing socioeconomic conditions in the population(5).

Table II__Prevalence and Incidence of Tuberculosis Infection in Various Studies

Authors	Years of study	Study area	Age group(yr)	N	Vaccination status	PPD strength	Cut off value	Prevalence rate (%)	Incidence rate
Chadha(2)	1996-97	Bangalore city	6-7	9340	BCG –ve (3687) BCG +ve (5653)	1TU 1TU	22 mm 20 mm	11.03 11.11 11.10	1.7 1.7 1.7
Chakraborty(6)	1974-75	Villages surrounding Bangalore	0-9	12535	BCG –ve	1TU	10 mm	4.9	–
Chadha(7)	1990-94	Bangalore	1–9	4575	BCG –ve	1TU	–	4.7-6.3	–
Chakraborty(5)		–	Slums of Bangalore Rural Bangalore	5-9 5-9	– –	– –	– –	– -	11.9 7.9
Present study	2001	Slums of Ahmedabad	0-14	210	BCG –ve	1TU	10 mm	30.4	5.4

TU = Tuberculin unit.

 

In the present study prevalence rate of tuberculosis infection is in conformity with the high prevalence and incidence of tuberculosis disease in the slums of Ahmedabad city (data not presented). It is stated that the existing structure of health services and their development, socio-economic and nutritional conditions of people, the nature and extent of their participation in the program all influence the general health of people and natural trend of tuberculosis in the community(8). A limitation of this tudy is its sample size; a large sample size is required to obtain adequate data on the infection rates.

Because of increased popoulation mobility due to urbanization, the socio-economic and environmental conditions became deplorable in slums of cities. The multiplicity of health care agencies and inappropriate diagnostic and treatment practices in the private sector in cities make the situation worse(2).

The association between poverty and tuberculosis is well established. Even within the developed world the highest rates of disease are seen in the poorest sections of the community(9). It is now obvious that the TB epidemic is growing larger and more dangerous each year. There has been no perceptible change in the epidemiology of TB since the National Sample Survey of 1956-57. The National Tuberculosis Control Program, after nearly four decades of its launch, has not been able to make a dent on the epidemiology of TB due to several operational and mana-gerial constraints although highly effective regimens of treatment are available(10).

This study was conducted during 2000-01 and thus represents data from recent years. This certainly points to the poor case finding and motivation activities for the National Tuberculosis Control Program. It is emphasized that the mere existence of a control program does not guarantee the involvement of workers in the community.

Acknowledgement

The authors are indebted to Dr. V.S. Rawal, Professor and Head, Department of Preventive and Social Medicine for his guidance. We are grateful to Commissionerate of Health for financial support.

Contributors: AB, AMK, MKL planned, coordinated and conducted the study, PJ, TP, MP collected the data. AB drafted the manuscript and will act as a guarantor for the manuscript.

Funding: Commisionerate of Health, Gujarat.

Competing interests: None stated.

 References

 

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