Trends in the prevalence of Pulmonary Tuberculosis over a period of seven and half years in a rural community in south India with DOTS.

Setting: Tiruvallur district In Tamil Nadu where DOTS was implemented by the State Government as the tuberculosis control measure in 1999, and monitored by the National Institute for Research in Tuberculosis for over five years. Objective: To estimate trends in TB prevalence in a rural community with DOTS. Design: Surveys of pulmonary tuberculosis were undertaken in representative samples of subjects aged >15 years (N = 83,000 – 92,000), initially and after two and half, five and seven and half years of implementation of DOTS. Sputa were collected from those with abnormal radiograph and/or presence of chest symptoms, and examined by direct smear and culture. Results: The prevalence of culture-positive tuberculosis was 607, 454, 309 and 388 per 100,000 in the four surveys, and that of smear-positive tuberculosis was 326, 259, 168 and 180. In the first five years; annual decrease was 12.4% (95% CI 10.4 - 14.4%) for culture-positive tuberculosis, and 12.2% (95% CI 8.0–16.2) for smear-positive tuberculosis. This was, however, followed by a significant increase in the next two and half years. The average new smear-positive case-notification rate was 75 per 100,000 during first four years but declined to 49 in subsequent years. There were no methodological differences during this period and information on changes in socio-economic indicators and nutritional standards was unavailable. Conclusion: Despite the average annual success rate (78%) in this tuberculosis unit being lower than the expected rate of 85%, the implementation of DOTS was followed by a substantial decrease in the prevalence of pulmonary tuberculosis over the seven and half year period. Our findings suggest that sustaining the high effectiveness of DOTS programme needs vigilant supervision.

Special considerations in the design, conduct and analysis of prophylaxis trials.

Methodological considerations in clinical trials apply to prophylaxis studies also. In addition, there are certain aspects that need special attention. These are the identification of a valid group of controls, the choice of the unit of randomization and its impact on subsequent analyses, the specificity and the sensitivity of case diagnosis and their impact on estimated efficacy and its reliability. The ethical aspects of the trial also need special consideration, bearing in mind that the intervention is on healthy individuals, and not patients with disease. These are discussed in the context of community prophylaxis trials of tuberculosis and leprosy undertaken in south India.

Lot quality assurance sampling for monitoring immunization coverage in Madras City.

OBJECTIVE: To explore the usefulness of Lot Quality Assurance Sampling (LQAS) to identify divisions in a city that had immunization coverage levels of 80% for any of the four EPI vaccines. METHODS: Only 43 divisions were considered for the study, the stratification factor being the death rate. The hypothesis that 80% coverage is 'unacceptable' was stipulated. Critical value (the number of unimmunized children) was chosen as 3. A simple random sample of 36 children in the age-group 12-23 months was taken from each selected division. Since sampling frames of children were not available, a simple random sample of 36 households was selected. Immunization status of each child was assessed by interviewing the child's mother/guardian. If the number of unimmunized children exceeded 3, then the division was regarded having coverage level 80% and rejected. RESULTS: The coverage was classified as unacceptable(i. e., below 80%) in 19 divisions for Polio and DPT vaccines, in 26 divisions for Measles vaccine and in 4 divisions for BCG vaccine. The average time spent for undertaking the LQAS survey was 6 man-days per division. CONCLUSION: This study demonstrated the utility of the LQAS technique in identifying 'unsatisfactory' pockets in Madras City, when the overall coverage was satisfactory. The technique will have greater application with an increase in the number of large units (cities/districts) having an overall coverage of 90% or more.

Randomised controlled field trial of two antenatal care packages in rural south India.

A randomised community intervention trial was undertaken in 12 subcentres in Karur health unit district, Tamil Nadu, to compare the efficacy of two antenatal care packages. A newly recommended 'high-risk' strategy package and a uniform package recommended by the Tamil Nadu Government were each implemented in 4 randomly selected subcentres by the study team, and the latter was also delivered by routine health services in the 4 remaining subcentres. Analyses were based on 294 pregnant women on the high-risk package (HR), 242 on the Tamil Nadu Government (TNG) package and 335 women in the control series. The HR package reduced the differences between the high-risk women and the others in mean haemoglobin and the percentages with preventable neonatal morbidity and low birth weight, and consequently the overall outcome was better in the HR series than in the TNG series. Finally, the results with the TNG package were better when it was implemented by the study team than by the routine health services, in terms of preventable maternal morbidity and preventable perinatal morbidity, but there was no impact on birth weight.

A concurrent comparison of a WHO-recommended 30-cluster survey and a modified version of it under Indian conditions in the estimation of immunization coverages.

A concurrent comparison of the WHO 30-cluster sample survey method for estimating immunization coverages (DPT, Polio, BCG, Measles) and an Indian modification of (GOI) was undertaken in five districts in South India. The essential difference between the two methods is the manner in which the first household is selected in the chosen clusters. With the WHO method, it is chosen clusters. With the WHO method, it is chosen at random, whereas with the GOI method it is often close to the village centre. Estimates with the required degree of precision, i.e., 95% confidence limits of +/- 10 percentage points, were provided in 18 (90%) of 20 instances by the WHO method and in 19 (95%) by the GOI method, findings which are in accordance with expectation. The estimated coverages were, however, higher by the GOI method than by the WHO method in two districts, lower in one district, and in the remaining two districts there was no clear pattern. On the average, there was a suggestion that the GOI method yielded slightly higher coverages, but the differences were not statistically significant.

Estimation of immunisation coverages in children by WHO 30-cluster survey.

A WHO 30-cluster survey for estimating immunisation coverages in infancy was undertaken in each of 5 districts in Tamil Nadu, strictly according to the specifications laid out in the WHO manual. The main aim was to examine whether the technique would provide estimates with the required degree of precision under Indian conditions. Of 60 sample survey estimates, 57 had the targeted degree of precision (i.e., 95% confidence limits of +/- 10 percentage points), which is in excellent agreement with expectation. The proportions of infants on whom immunisation was initiated, were very high for DPT vaccine (88-99%) and polio vaccine (85-99%); however, of those who had received the first dose, 23-39 per cent did not complete the 3-dose schedule. Estimated coverage with measles vaccine ranged from 15 to 54 per cent, while BCG coverage ranged from 53 to 97 per cent. Better health education regarding the need and correct age for immunisation, and more effective motivation at the time of administration of the first dose of DPT/polio vaccine, are recommended.

Confidence intervals in medical research.

The utility of confidence intervals in a wide variety of situations in the medical field is re-emphasized, with examples drawn from controlled clinical trials, disease control programmes, vaccine trials and laboratory studies. It is shown that the confidence interval approach is more informative than a mere test of statistical significance, and should therefore be employed as an useful adjuvant. Since proportions are widely quoted in medical literature and as the determination of the exact confidence limits for a binomial proportion is iterative and time-consuming, an assessment is made of 15 published methods which provide approximate confidence limits; the 'Square root transformation' method is recommended since it is accurate and the computation of limits is relatively easy. In the case of a difference between two proportions, the usual method may be employed if sample sizes exceed 75; for smaller sample sizes (even for sizes of 5), the Jeffreys-Perks method is very satisfactory and is therefore recommended.

Some indices pertaining to the leprosy control programme in Tamil Nadu, based on data from a random sample of fourteen government control units.

From a random sample of 14 Government Leprosy Control Units in Tamil Nadu, information on the profile of the newly-diagnosed leprosy patients and some important aspects of the control programme in 1978-81 was collected when monotherapy with dapsone was the practice. Among the new patients, 55 per cent were males, 24 per cent were children, 6 per cent had lepromatous leprosy and 9 per cent had a deformity. About 65 per cent were detected by active case-finding methods and 25 per cent were voluntary referrals. Of the total diagnosed patients, only 68 per cent started treatment; further, of these, about 40 per cent collected drugs for at least 6 months in the first year of treatment. The average attendance at the clinic was 34 per cent of the due attendance. Coverage in the annual examination of family contacts was 57 per cent. During the 4 yr period, about 70 per cent of the villages had population surveys with a coverage of 75 per cent or more. The introduction of multi-drug therapy has provided a new impetus to the programme and therefore a similar study is called for to provide valuable information about the extent of improvement in completion rates and overall impact.

A 20-year study of the Leprosy Control Programme at the Hemerijckx Leprosy Centre in Polambakkam in South India.

The Hemerijckx leprosy centre at Polambakkam in South India covers a rural population of about 800,000 and has treated over 40,000 cases of leprosy during the period 1955-75. Based on a stratified random sample of 25% of the case records, information was obtained about the profile of newly-detected cases in various cohorts (1955-57, 1958-60, 1961-64, 1965-69, 1970-75), regularity in drug collection and response to treatment. In newly-detected cases, the ratio of males to females was stable (3:2), but the proportion of adults aged 45 years or more increased from 15% in 1958-60 to 20% in 1970-75 and the lepromatous rate decreased from 9% to 6%; the proportion deformed at the time of diagnosis ranged from 11% to 15%. Regularity in drug collection was unsatisfactory even in the first year of treatment, with less than half the patients making 6 (or more) of the 12 monthly drug collections. The clinical status at 4-6 years was known for 70-75% of the patients who started treatment and of those approximately 60% had inactive or arrested disease. Data from population surveys was sparse; about 60% of the expected numbers were initiated and less than 30% of these had a coverage of 75% or more. The limited evidence, however, showed a decline in the prevalence of about 2 per thousand per annum. Field studies to evolve strategies for better motivation of patients, introduction of short-course regimens, and continuous monitoring of the programme are urgently needed.