Prevalence of systemic lupus erythematosus in India.

Prevalence of systemic lupus erythematosus (SLE) was studied in the northern Indian population by means of a two-pronged approach: (a) antinuclear antibody (ANA) screening of the general population by a new well-standardized finger-prick 'filter paper' technique (sensitivity and specificity: 95.4% and 86.2%, respectively); and (b) a questionnaire survey carried out primarily by trained personnel in the community (sensitivity and specificity: 100% and 68.6% respectively). The low specificity of the two methods was improved by the introduction of a step of secondary screening by the authors, thus excluding false positives. ANA screening of 52,062 individuals yielded 13 positive results, of which only two were found to be true cases of SLE after secondary screening. Questionnaire survey of 39,826 individuals similarly yielded 3393 positive results. On secondary screening, only one of these persons was found to be a case of SLE. Thus, three cases of SLE were detected in a population survey of 91,888, giving a point prevalence of 3.2 per 100,000 (95% CI = 0-6.86 per 100,000). The reported prevalence of SLE ranges from 14 to 60 per 100,000. Thus, the prevalence of SLE in India is comparatively low. Although the reasons for low prevalence are not clear, the study used highly sensitive methodology and it is therefore unlikely that SLE cases were missed. It is hypothesized that SLE is a disease of modernization and therefore its prevalence in a predominantly rural population like that of India is low.