The problem in using simple tools e.g. chest symptoms for epidemiological surveys, designed to quantify the problem is that estimates from these simple surveys are considerable underestimates. Recent research has, however, paved the way for the use of these simpler tools for use in estimating tuberculosis case prevalence rates in the community. A tool which is simple, convenient to use and maintain, cheap but highly sensitive is called "screening tool". Such tools are used for making initial selection of the given population. Tuberculin test, X-ray & symptom elicitation are the main screening tools used for epidemiological surveys and TB Control Programme. In the programme, symptom elicitation and X-ray examination are the screening tools of choice for Case-finding. In the survey, tuberculin and X-ray are the only two tools used, although tuberculin is not a good screening tool (40% population infected). Use of symptom screening in surveys, however, is restricted in the absence of adequate information on comparison of prevalence rates obtained by this method of screening with the best estimate. The performance of symptom screening with either culture or smear microscopy have been attempted. They showed that by applying suitable correction factors they may be rendered comparable to the best estimate. The symptoms may be useful in the survey as a screening tool and may give the rates as proximate to the true rates as possible. They will enable considerable simplification of epidemiological studies in tuberculosis without compromising on the precision of the estimates arrived at.

Screening of the population by Mass Miniature Radiography (MMR) followed by sputum examination by culture of the X-ray abnormals is the customary method for arriving at the prevalence rate of cases in the community. It is not possible to use this methodology by states to carry out prevalence surveys in these areas, even if they desire to evaluate the effect of anti tuberculosis measures implemented by them. Therefore, simpler means of screening population through chest symptom for sputum examination has been studied by National Tuberculosis Institute (NTI). The objectives of the present investigation were to find out the prevalence of bacillary cases by screening the population through identification of chest symptomatics by Social Investigators (Sls) or General Health Workers (GHWs) compared to that by MMR. In a peri urban area 10 kms away and around Bangalore city all the villages were listed and of the 60 villages were selected on the basis of a sample random sample. Of them, 30 were covered by Sls of NTI and the other 30 by GHWs of the state government. The methodology adopted was that (1) After census taking and registration of the entire population aged 15 years and above, Sls questioned the persons house to house for presence of cardinal chest symptoms of any duration. All chest symptomatics were subjected to MMR and sputum examination. (2) Similar methodology was adopted by GHWs in the other 30 villages allotted to them. (3) Without knowing the symptom status of all the registered persons, aged 15 years and more belonging to all the 60 villages, were subjected to MMR and from among those having X-ray abnormalities, to sputum examination.

It was found that GHWs had identified the same proportion of the persons either having general symptoms or having chest symptoms from the general population, as Sls. Prevalence rates of culture positive as well as smear positive cases were similar by any of the three methods i.e., 0.18%, 0.23% & 0.25% respectively. Prevalence rates of smear positive cases obtained through symptom questioning, either by Sls or GHWs, were more or less similar to the estimates obtained by the more comprehensive screening method of MMR and/or symptom questioning. The culture positive prevalence rate following MMR screening was 0.25%, which was lower than the rates observed in other surveys. The paper discusses the possible hypothesis that could explain the observation. It also presents correction factors to compute rates comparable to the best estimate i.e., that obtained through comprehensive screening by MMR and/or symptom questioning, followed by sputum culture.

Persons suffering from pulmonary tuberculosis generally experience symptoms such as cough, chest pain, fever and haemoptysis. It is possible to identify the symptomatics by interviewing them during community health surveys. The symptom survey was carried out in 62 villages and 4 town blocks of Tumkur district in Karnataka as a sequel to an epidemiological survey undertaken to estimate the prevalence of tuberculosis. The data was collected through structured schedule. The interviewers were given the identification details of individuals having X-ray shadows suggestive of tuberculosis and an equal number of matched controls within 4 weeks of the survey. A total of 1752 persons were taken into the study of whom 875 had x ray shadows and 877 were normals. Of the total persons under study 89.7% were satisfactorily interviewed. It was observed that 42.6% of the total symptomatics gave history of one symptom at the first general question, 13% responded having symptoms after being asked specific questions. In conclusion a 42.6% affirmative response to the initial question of 'How is your health' is noteworthy that an investigator is acceptable health agency as the interviewee is willing to confide in him regarding his health problems. Additional number of persons responded to direct specific questions.

It must be pointed out that interview is a generic term applied to a tool that may be used for obtaining information through verbal communication. As a tool in surveys for screening for tuberculosis it is amenable to divese techniques and has great potentialities of being applied to different situations and various categories of respondents. Hence, it is necessary to identify the nature of data to be obtained and to decide on the technique that would be most suitable. Proper training, skill and supervision of the interviewer can obviate any possible bias and subjectivity that could vitiate an interview. As compared to many of the tools of social science research, the interview is simple, easy and amenable to being used in live situations. It is also of prime importance among populations for whom vocalisation is the most important medium of communication. Hence, in a community survey for the estimation of the prevalence of chest symptomatics the interview can be a valuable tool. It also shows that the interview is adequate as a tool of community survey in tuberculosis.