Trends in prevalence and case finding in the ALERT leprosy control programme, 1979-1999.

From 1979 to 1999, the ALERT leprosy control programme has covered a well-defined area in central Ethiopia using standardized case finding strategies. During this period, the leprosy prevalence has decreased more than 30-fold, there has been a 3-fold decrease in case detection and a 6-fold decrease in the case detection rate. The proportion of MB patients among new cases increased by around 80% and the proportion of children among new cases decreased by around 60%. Several factors may have contributed to these trends. The impact of the introduction of MDT and the shortening of the duration of the MB regimen are shown, but other factors are also discussed at length: an increase in the population of the area, cleaning up of the registers, changing case definitions, changes in staff motivation and fluctuations, even small ones, in case finding intensity and coverage. Do the observed trends reflect a reduction in the transmission of the leprosy infection? Because of the many confounding factors, it would be difficult to answer that question positively at present. Additional rigorous data collection and analysis is required.

Which physical signs help most in the diagnosis of leprosy? A proposal based on experience in the AMFES project, ALERT, Ethiopia.

As integration of leprosy control programmes proceeds, general health staff will have responsibility for the diagnosis of most new cases of leprosy. The training required by these workers has not yet been set out in detail. In this paper the criteria for making the diagnosis of leprosy in the AMFES cohort of 594 new cases are examined. Since this study does not include details of suspects in whom leprosy was excluded on clinical grounds, true sensitivity and specificity values cannot be calculated, but the positive predictive value of the diagnostic criteria can be measured. Sensory loss in a typical skin patch is the most important sign of early leprosy, but was not present in 132 (49%) of the 268 cases with a positive skin smear. Thickening of the ulnar nerve is a valuable sign of leprosy in Ethiopia. It can be taught to health workers, who can practise by examining their own ulnar nerves. It is more likely to be present than nerve function impairment and is particularly important when skin smears are difficult to do or are unreliable. We recommend that five basic signs are used, the presence of any two being diagnostic of leprosy: Skin lesion(s) consistent with leprosy. Loss of sensation in such a lesion. Thickening of either ulnar nerve. Loss of sensation in the palm of the hand or the sole of the foot. The presence of acid-fast bacilli in skin smears. Exact policies for the diagnosis of leprosy should be worked out and validated for each national programme.

Classification of leprosy cases under field conditions in Bangladesh. I. Usefulness of skin-smear examinations.

In 2 non-governmental organization projects in Bangladesh 244 new leprosy patients were classified in the field according to clinical criteria. Skin smears were taken at 4 standardized sites and at the most active peripheral lesion, where a biopsy was also taken. Comparison of the clinical field classification with the results of the skin smears and biopsies gives a sensitivity of 92.1% for the clinical criteria, but a specificity of only 41.3%. The skin-smear results, on the other hand, have a sensitivity of 88.4% and a specificity of 98.1%. Thus, skin smears may contribute considerably to the operational classification of leprosy patients under field conditions. Quality control of the peripheral laboratory is essential. Appropriate site selection for the smear taking will also contribute to increased performance. Analysis of the skin-smear results suggests that the policy of taking smears at standardized sites should be abandoned in favour of the earlobes and active peripheral lesions.

Classification of leprosy cases under field conditions in Bangladesh. II. Reliability of clinical criteria.

In 2 non-governmental organization projects 244 new leprosy patients in Bangladesh were classified in the field according to clinical criteria i.e. number of skin lesions and number of enlarged nerves. Comparison of these classification results with the results of skin smears and biopsies yielded a sensitivity (for detection of a MB case) of 92.1%, but the 'unconfirmed MB rate' amounted to 52.6%. In order to improve the reliability of the operational classification, several additional clinical criteria were investigated. It was found that neither the presence of anaesthesia in the skin lesions nor the presence of grade 2 disabilities or peripheral anaesthesia or voluntary muscle testing (VMT) impairment contributed to an improved classification. Counting the number of body areas showing signs of leprosy, which had proven very useful in other programmes, did not result in a more reliable classification in the 2 projects in Bangladesh. The presence of clinical signs of lepromatous leprosy, more specifically nodules or diffuse infiltration, could be a useful addition to the classification criteria. If the sensitivity must remain higher than 90%, the lowest 'unconfirmed MB rate' obtainable in Bangladesh, using clinical criteria only, is 46.4%, for a sensitivity of 91.0%. However, the inclusion of skin-smear results in the classification criteria could improve the sensitivity to 96.6% and lower the 'unconfirmed MB rate' to 40.3%. A reduction in MB overclassification will result in more efficient and more cost-effective leprosy control programmes.